Scientists have developed new eye drops that allow mouse eyes to perform certain steps of photosynthesis.

The drops, which contain photosynthetic machinery extracted from spinach leaves, use light-driven reactions to improve symptoms of dry eye disease, according to a study published May 15 in the journal Cell. Although the researchers tested the drops in mice, the hope is that with further testing, the therapy could be used in people someday.

The study is a "cool application" of engineering inspired by symbiotic relationships in nature, said Corey Allard, a cell biologist at Harvard Medical School who was not involved in the work.

Plants rely on photosynthesis to make energy, in the form of glucose, from sunlight. Organelles called chloroplasts conduct photosynthesis and give plants their green color. While no animals photosynthesize naturally on their own, a few have developed symbiotic relationships with photosynthetic algae that let them harness solar power. Some species of sea slug, including leaf sheep (Costasiella kuroshimae) and the mangrove leaf slug (Elysia bangtawaensis), even steal chloroplasts from algae they eat.

In the new study, David Tai Leong, a chemical engineer at the National University of Singapore, and colleagues tested whether mammal eyes could tolerate similar behavior, in hopes of pointing to a way to treat dry eye disease, which affects the film of tears covering the eye and produces oxidants and inflammation that can impair vision.

To create the eye drops, the team first removed stacked compartments called thylakoid grana from chloroplasts in spinach. Thylakoid grana are the chlorophyll-bearing structures inside chloroplasts where the first, light-dependent steps of photosynthesis occur. Then, the team encapsulated those thylakoid stacks in tiny packages to create a system they dubbed "light- reaction enriched thylakoid NADPH-foundry," or LEAF.

When incorporated into eye drops, LEAF reduced eye inflammation in mice induced to have dry eye disease. Along the path to making glucose, chloroplasts produce a chemical called NADPH at the thylakoid grana. NADPH acts as an antioxidant, and it helped to eliminate compounds that were exacerbating eye inflammation in the mice.

After five days, the mice treated with the LEAF eye drops were comparable to mice treated with an existing, commercially available medicine to treat dry eye disease. They showed greater tear production and reduced cornea damage compared with the mice that received only saline eye drops.

"The eye is uniquely suited for this type of strategy, since light is already an intrinsic component of its normal physiological function," Dr. Xianfeng Lin, an orthopedic surgeon at Zhejiang University School of Medicine in China, wrote in an email to Live Science. Although Lin wasn't involved with the new work, he and colleagues published a 2022 study in the journal Nature using a similar photosynthetic system to combat inflammation from arthritis in mouse knees.

"The work extends the role of light in the eye from being purely sensory to potentially contributing to local metabolic support and tissue repair," Lin said.

Even though the eye drops contain chlorophyll, the concentration is very low, and the drops appear transparent.

"We are able to use a highly optimized photosynthetic machine, so we do not need huge amounts of the LEAF system," Leong said. "Because it's so low concentration, you can't see the green color. So we won't have green eyes like the Incredible Hulk."

The eye drops aren't ready for human use yet; they still need to undergo extensive testing for safety and long-term efficacy. But the team is working to set up a clinical trial that will first look at safety, Leong told Live Science.

If approved for human use, the medicine would take advantage of how our eyes naturally work, since it only requires ambient light to activate. A patient would be "receiving a therapy that is aligned with how we normally go about our day," Leong said.

The sun has been Earth's constant companion ever since our planet emerged. But if the sun were to suddenly disappear, what would happen to our home planet?

To understand the fate of a sunless Earth, it's important to know how both arose. The sun formed about 4.6 billion years ago, when a massive spinning cloud of gas and dust collapsed in on itself and condensed, creating the biggest object in what would become our solar system and eventually reaching a temperature of 27 million degrees Fahrenheit (15 million degrees Celsius) at its core.

Much of the remaining material nearby then clumped up to form Earth and the other rocky planets, including Mercury, Venus and Mars, as well as moons and asteroids. Since its formation, Earth has been heavily reliant on its star. The sun's gravitational pull keeps our planet in orbit in the "Goldilocks zone," the just-right distance from its star where it's not too hot or too cold for water to exist as a liquid on a planet's surface. The sun also drives photosynthesis and water cycles, and it provides sunlight and heat, which influence our climate. Plus, the sun's ultraviolet light helps our bodies make vitamin D, which is needed for healthy bones and teeth.

If the sun suddenly vanished, Earth and the vast majority of life would be in dire straits. It would start "a ticking time bomb on the survival of every living thing on earth that relies on photosynthesis, which is the vast majority of surface life and all of humanity," Timothy Cronin, an associate professor of atmospheric science at MIT, told Live Science over email.

For at least 8 minutes, 20 seconds, no one would know the sun went missing ‪—‬ that's how long it takes light from the sun to reach Earth. During that time, "we'd almost certainly have no idea that anything had happened," Cronin said.

Then, the real trouble would begin.

After the sun's eight-minute swan song, there would be "a sudden blackout," Cronin said. Without sunlight, artificial lighting from electricity, oil or gas would be the main ways we could still generate light, along with fire, bioluminescence and fluorescence. We'd lose track of day and night. The moon, which reflects the sun's light, would go completely dark, although distant stars in the sky would still be visible. And without the sun's mass and gravity keeping the planets and other celestial bodies in orbit, "all the planets would fly off in the direction of their current travel," Cronin said.

But humanity would have more immediate problems than flying off into interstellar space. No sunlight would mean crucial processes, such as growing food, would become much more complicated.

Photosynthetic organisms would be done for, Michael Summers, a professor of planetary sciences and astronomy at George Mason University in Virginia, told Live Science. Most plants that weren't grown under artificial lighting would quickly suffer. And while some "might stay dormant for weeks to months, like they do in the wintertime, eventually all photosynthetic organisms would die."

Fungi, meanwhile, feed on living or dead matter, and "there would be a great deal of dead material available," Summers said. So fungi likely wouldn't die from a lack of food, but from the cold.

Cold planet

It wouldn't take long for frigid temperatures to change the Earth as we know it.

At first, Earth would cool by an average of roughly 36 F (20 C) every 24-hour period, Summers said. "That plunges almost the whole world into subfreezing temperatures within just two to three days," although as it got colder, the temperature change per day would decrease, he said. Small ponds might freeze over within a week, whereas lakes might take weeks or months. The oceans could persist "for many years, maybe decades," and in certain places, like "the deepest parts of the oceans where you have volcanoes, they might stay liquid for potentially as long as the volcanoes last," Summers said. "And that could be billions of years."

To understand how cold Earth would ultimately get, let's consider Pluto. Right now, Pluto is "about 40 times as far from the sun as Earth is, and the temperature there now is about minus 400 degrees Fahrenheit [minus 240 C]," Summers said. "Once you eject the Earth out of our solar system, it's going to get much further away than Pluto very quickly."

But Earth's temperature wouldn't reach absolute zero, thanks to the Big Bang that happened around 13.8 billion years ago. Even "the lowest temperatures in the universe are limited by heat that's left over from the Big Bang," Summers said. "Take any object very far away from a star and let it cool for a million years," and it will still remain a few degrees above absolute zero. The temperature of the leftover radiation known as the cosmic microwave background is about minus 454 F (minus 270 C), whereas absolute zero is slightly chillier at about minus 459 F (minus 273 C).

At an ultracold temperature, human civilization and most of life would almost certainly collapse. "It's conceivable that people could survive underground in caves, sustained by geothermal or nuclear energy, with plants grown under artificial lighting," Cronin said, "but this would be an extinction event to make all others look puny."

What would survive?

One thing that might survive? Near-microscopic animals called tardigrades, also known as water bears. "Ugly little critters," Summers said, but "hard to kill." They can be zapped with radiation or immersed in certain types of alcohol and still survive; perhaps hitting them with a hammer would kill them, he suggested. "Otherwise, they're pretty much one of the hardiest forms of life on Earth."

Likewise, bacteria that don't require photosynthesis, such as types that live around deep ocean vents, would likely survive. That's because certain microbes, including some bacteria and archaea, use chemosynthesis, as opposed to photosynthesis, to "live off of chemical bonds in rocks and minerals," Summers added.

Fortunately for humanity, there is no reason to believe the sun will vanish in the blink of an eye. Over time, however, the sun will die. It will continue to create heat and light for another 5 billion years or so, but once its fuel runs out, it will expand into a red giant, swallowing Mercury and Venus and perhaps Earth. Regardless, humans likely won't last that long; the sun's gradual increase in brightness is expected to vaporize Earth's oceans in a little over a billion years from now.

While those impacts may be a long way away, Summers said it's important to consider the potential outcomes. When "we understand more about stars and how they can change over time, on short timescales and on long timescales, we understand the universe better."

Sun quiz: How well do you know our home star?

Mass tree planting in China is turning one of the world's largest and driest deserts into a carbon sink, meaning it absorbs more carbon from the atmosphere than it emits, new research reveals.

The Taklamakan Desert (also spelled Taklimakan or Takla Makan) is slightly larger than Montana, stretching across about 130,000 square miles (337,000 square kilometers). It is encircled by high mountains, which block moist air from reaching the desert for most of the year, creating extremely arid conditions that are too harsh for most plants.

However, over the past few decades, China has sowed a forest around the Taklamakan's edges, and a new study suggests this approach is beginning to bear fruit.

"We found, for the first time, that human-led intervention can effectively enhance carbon sequestration in even the most extreme arid landscapes, demonstrating the potential to transform a desert into a carbon sink and halt desertification," study co-author Yuk Yung, a professor of planetary science at Caltech and a senior research scientist in NASA's Jet Propulsion Laboratory, told Live Science in an email.

Over 95% of the Taklamakan Desert is covered in shifting sand, meaning it has long been considered a "biological void," according to the study. The desert has been growing since the 1950s, when China underwent massive urbanization and farmland expansion. This conversion of natural land created the conditions for more sandstorms, which, in general, blow away soil and deposit sand instead, causing land degradation and desertification.

In 1978, China implemented the Three-North Shelterbelt Program, a huge ecological engineering project intended to slow desertification. Also called the "Great Green Wall," the project aimed to plant billions of trees around the margins of the Taklamakan and Gobi deserts by 2050. More than 66 billion trees have been planted in northern China to date, but experts debate whether the Great Green Wall has significantly reduced the frequency of sandstorms.

China finished encircling the Taklamakan Desert with vegetation in 2024, and researchers say the effort has stabilized sand dunes and grown forest cover in the country from 10% of its area in 1949 to more than 25% today.

Now, scientists have found that sprawling vegetation in the Taklamakan Desert's periphery is absorbing more carbon dioxide (CO₂) from the atmosphere than the desert is releasing, meaning the Taklamakan may be transforming into a stable carbon sink.

The researchers analyzed ground observations of different vegetation-cover types, as well as satellite data showing precipitation, vegetation cover, photosynthesis and CO₂ fluxes in the Taklamakan Desert over the past 25 years. They also used the National Oceanic and Atmospheric Administration's Carbon Tracker, which models CO₂ sources and sinks globally, to bolster their findings.

The results, published Jan. 19 in the journal PNAS, show a long-term trend of expanding vegetation and rising CO₂ uptake along the desert's edges that coincides both in time and space with the Great Green Wall.

Over the study period, precipitation during the Taklamakan Desert's wet season from July to September was 2.5 times higher than it was in the dry season, averaging about 0.6 inches (16 millimeters) per month. Precipitation enhanced vegetation cover, greenness and photosynthesis along the desert's margins, thereby lowering CO₂ levels over the desert from 416 parts per million in the dry season to 413 ppm in the wet season.

Previous research indicated that the Taklamakan Desert may be a carbon sink, but those studies focused on CO₂ that is absorbed by the desert's sand. They also suggested that sand is not a stable carbon sink under climate change, because rising temperatures can cause air in the sand to expand, which releases extra CO₂.

"Based on the results of this study, the Taklamakan Desert, although only around its rim, represents the first successful model demonstrating the possibility of transforming a desert into a carbon sink," Yung said.

The Great Green Wall's potential to slow desertification remains unclear, but its role as a carbon sink "may serve as a valuable model for other desert regions," he added.

Scientists in Switzerland have created a new "living" material that contains blue-green algae and could one day be used in buildings to fight climate change, they say.

Thanks to the blue-green algae, or cyanobacteria, the new material is photosynthetic. This means it can chemically convert carbon dioxide (CO₂), sunlight and water into oxygen and sugars, which promote growth.

In the presence of certain nutrients, the material can also convert CO₂ into solid carbonate minerals, such as limestone, the researchers said in a new study, published April 23 in the journal Nature Communications. Over time, these minerals build a robust lattice inside the material that strengthens it and stores carbon in a more stable form than photosynthesis does.

"The material can store carbon not only in biomass, but also in the form of minerals — a special property of these cyanobacteria," study co-author Mark Tibbitt, an associate professor of macromolecular engineering at the Swiss Federal Institute of Technology (ETH) Zurich, said in a statement. "As a building material, it could help to store CO₂ directly in buildings in the future."

Without the ability to sequester carbon in mineral form, the new material would be floppy and jelly-like. But by producing a mineral skeleton with CO₂ and nutrients, the material gradually enhances its own mechanical strength, making it a good candidate for construction, according to the study.

The researchers suggest the material could one day be used as a coating on building facades to suck CO₂ directly out of the atmosphere. In the study, the material continuously sequestered CO₂ for 400 consecutive days, storing approximately 26 milligrams of CO₂ per gram of material in the form of carbonate precipitates. This rate is highly efficient and significantly higher than other forms of biological CO₂ sequestration, the researchers said.

Related: New wonder material designed by AI is as light as foam but as strong as steel

The material's increasingly vibrant green color is evidence that it stores CO₂ in the form of biomass. But cyanobacteria can only grow so much, and the rate at which carbon was stored inside the bacterial cells leveled out after about 30 days, according to the study. This means that carbon sequestration in the form of biomass decreases beyond this timeframe, but it doesn't stop.

The base of the new material is a 3D printable hydrogel — a gel with a high water content made of cross-linked molecules. The researchers selected a porous hydrogel and grew cyanobacteria inside it, ensuring that enough light, water and CO₂ could penetrate the gel to reach the bacteria. The scientists then tested different shapes of hydrogel to determine the best geometry for cyanobacteria survival.

"Cyanobacteria are among the oldest life forms in the world," study co-author Yifan Cui, a doctoral student in macromolecular engineering at ETH Zurich, said in the statement. "They are highly efficient at photosynthesis and can utilize even the weakest light to produce biomass from CO₂ and water."

In the study, the researchers bathed the hydrogels in artificial seawater to supply the necessary nutrients for mineral precipitation. Further research is needed to determine how those nutrients, which include calcium and magnesium, could be injected into the material if it was coating a building.

In the meantime, the researchers are dreaming up different shapes that the material could take. At an architecture exhibition in Venice, the team presented their material in the form of two tree trunk-like objects that could each absorb up to 40 pounds (18 kilograms) of CO₂ per year — or as much as a 20-year-old pine tree, according to the statement.

It might be possible to genetically engineer cyanobacteria to increase their photosynthetic rates before embedding them in the material, the researchers noted in the study.

"We see our living material as a low-energy and environmentally friendly approach that can bind CO₂ from the atmosphere and complement existing chemical processes for carbon sequestration," Tibbitt said.

Plants are an incredibly diverse group of organisms, ranging from tiny algae to majestic redwood trees. Plants have colonized nearly every environment on Earth, evolving ways to thrive in blistering deserts, salty coastlines and dripping rainforests. They support most life on Earth because they sit at the base of almost every food chain and pump out the oxygen we need to breathe.

Most plants have green leaves, and many have beautiful-smelling flowers that come in many sizes and every color of the rainbow.

Plants often rely on wind, water and animals (like bees, butterflies or birds — known as pollinators) to reproduce. To do so, plants transfer pollen from a male flower to a female flower. This process creates a seed, which then grows into a new plant that gets half its genes from the male "parent" and half from the female "parent." Some plants make more of themselves without this transfer process, creating a new plant that's essentially a clone of itself, meaning it carries all the same genes as its parent.

5 fast facts about plants

• Plants can communicate with each other by releasing chemicals when they are under attack.
• Despite not having brains, some plant species can "remember" things from the past and react accordingly.
• Some plants, like Venus flytraps, eat animals like flies or frogs.
• There are around 390,000 plant species in the world.
• Plants first evolved in the water, and then started growing on land about 400 million years ago.

Everything you need to know about plants

Plant pictures

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• Where did the 1st seeds come from?
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The emergence of human life may not have been as improbable as scientists once thought, a new model suggests. The finding increases the likelihood of intelligent life elsewhere in the universe, the researchers say.

Previously, scientists assumed that for human life to emerge on Earth, it needed to pass through a series of "hard steps" — flukes in evolution that are incredibly unlikely to occur within the lifetime of an average star. This makes our position as intelligent observers of the universe a rare occurrence and our chances of finding intelligent aliens low.

But a new model has challenged this decades-old assumption by proposing that human intelligence wasn't a long shot but instead an outcome that unfolded according to predictable geological processes. The researchers published their findings Feb. 14 in the journal Science Advances.

"We're arguing that intelligent life may not require a series of lucky breaks to exist," lead author Dan Mills, a researcher at the University of Munich, said in a statement. "Humans didn't evolve 'early' or ‘late' in Earth's history, but 'on time,' when the conditions were in place. Perhaps it's only a matter of time, and maybe other planets are able to achieve these conditions more rapidly than Earth did, while other planets might take even longer."

First proposed by physicist Brandon Carter in 1983, the hard steps model is an attempt to explain why humans emerged on Earth so late in the life of the sun — roughly 4.5 billion years into its 10 billion-year lifespan. Carter reasoned that intelligent life evolved through a chain of highly improbable evolutionary events — the formation of replicating molecules, the emergence of RNA and DNA, the evolution of multicellular organisms, and the inventions of sex and language.

Related: Alien life may look nothing like life on Earth — so how should we go about looking for it?

Carter's proposal quickly took root in astrobiology, encouraging the view that our own evolution was a remarkably uncommon accident and that the odds of us encountering human-like beings elsewhere in the universe was, therefore, dishearteningly low.

But it may not be true after all, the new research suggests. By combining expertise in physics and geobiology, they studied the key steps that led to the evolution of life on our planet.

This produced a model that explains our origins through the sequential openings of key "windows of habitability," such as oxygen and nutrient availability, ocean salinity and sea surface temperatures. According to this model, human life didn't emerge late on our planet but simply when the planetary conditions were right.

"We're taking the view that rather than base our predictions on the lifespan of the sun, we should use a geological time scale, because that's how long it takes for the atmosphere and landscape to change," Jason Wright, a professor of astronomy and astrophysics at Penn State and a co-author of the paper, said in the statement. "These are normal timescales on the Earth. If life evolves with the planet, then it will evolve on a planetary time scale at a planetary pace."

To test this new proposal, the researchers outlined a number of research projects that include testing unicellular and multicellular organisms at extreme temperatures and oxygen levels to ascertain the range of conditions in which they could have emerged. They also proposed scanning the atmospheres of distant exoplanets for key biosignatures, such as the existence of oxygen, and searching the evolutionary record for signs that singular innovations on the path to human life (such as photosynthesis and eukaryotic cells) evolved more than once.

"This is a significant shift in how we think about the history of life," co-author Jennifer Macalady, a professor of geosciences at Penn State, said in the statement. "It suggests that the evolution of complex life may be less about luck and more about the interplay between life and its environment, opening up exciting new avenues of research in our quest to understand our origins and our place in the universe."

Tiny photosynthetic microbes could be secretly thriving on Mars — hiding inside small bubbles of liquid water in the thin layers of dusty ice that litter the Red Planet's surface, a new NASA-led study reveals.

Researchers believe the icy patches could be among the most promising targets in the hunt for extraterrestrial life within our solar system — and plan to recreate them in the laboratory on Earth to test the predictions.

Mars is a surprisingly icy world: The planet has frozen sand dunes covering its north pole, giant slabs of carbon dioxide ice above its south pole and massive chunks of frozen water buried near its equator. However, it also has smaller sub-zero features, including patches of dusty water ice left behind by ancient snow drifts that clung to specific spots on the planet's surface, such as the bottoms of gullies and ravines.

In a new study, published Oct. 17 in the journal Communications Earth and Environment, researchers created computer models to simulate the conditions within this dusty surface ice and found that it could contain tiny bubbles of meltwater, which can act as miniature "habitable zones" for microbial life left over from Mars' watery past.

The researchers proposed that the hidden cavities could provide single-celled organisms with three key requirements for photosynthesis: liquid water, carbon dioxide gas from Mars' wispy atmosphere and sunlight, which shines through the thin ice above. The ice could also theoretically shelter microbes from potentially deadly solar radiation and cosmic rays, which bombard Mars' surface because of the planet's lack of magnetic shielding.

Related: NASA may have unknowingly found and killed alien life on Mars 50 years ago, scientist claims

It would be easy for future astronauts and colonists to reach the dusty ice and find these bubbles, which makes them an even more appealing place to look for extraterrestrial life, the researchers wrote. "If we're trying to find life anywhere in the universe today, Martian ice exposures are probably one of the most accessible places we should be looking," study lead author Aditya Khuller, a planetary scientist at NASA's Jet Propulsion Laboratory, said in a statement.

According to the researchers, grains of dark-colored dust buried beneath thin layers of surface ice can be heated by sunlight shining through the ice, creating pockets of space that fill up with melting water. This is perhaps one of the only places where liquid water could readily form on Mars because ice normally sublimates — or turns directly into gas — when it gets heated, the researchers wrote.

A similar process happens on our planet: When dust gets trapped within snow, glaciers and ice sheets, it creates spaces known as cryoconite holes, which often contain liquid water — and sometimes life.

"This is a common phenomenon on Earth," study co-author Phil Christensen, a planetary scientist at Arizona State University, said in the statement. "Dense snow and ice can melt from the inside out, letting in sunlight that warms it like a greenhouse, rather than melting from the top down."

A wide variety of photosynthetic organisms live in cryoconite holes, such as algae, fungi and cyanobacteria. During winter, when temperatures drop and the holes refreeze, these lifeforms enter into a hibernation-like stasis where they effectively pause all key functions until the holes reform in summer, the researchers wrote. Any potential Martian microbes may do something similar, they added.

Based on the new computer models, researchers think that the meltwater bubbles could form in ice up to 9 feet (3 meters) deep, as long as the dust content is low (less than 1%). However, this is only likely to happen at latitudes between 30 degrees and 60 degrees. Any closer to the planet's poles, and the ice will likely be too cold for bubbles to form.

The team plans to continue studying this proposed phenomenon, using additional computer models and Earth-based experiments to learn more about how and where it might happen.

"I am working with a team of scientists to develop improved simulations of if, where, and when dusty ice could be melting on Mars today," Khuller told Live Science's sister site Space.com. "Additionally, we are recreating some of these dusty ice scenarios in a lab setting to examine them in more detail."

Plants can grow with much less light than previously thought, according to a new study on tiny water-based organisms called microalgae that has been published in Nature Communications. The German-led team of researchers lowered light sensors into Arctic water to a depth of 164 feet (50 metres) to test how low light levels must become before plant life ceases to exist, with incredible results.

They found that plants were able to perform photosynthesis — the process in which their leaves convert sunlight into energy — with very little light indeed. Not only did the microalgae carry out this process at the lowest light levels ever recorded (just 0.04 micromoles of photons m⁻²/s⁻¹), this wasn't very far from what computer simulations predict to be the lowest light possible in any circumstances (0.01 micromoles of photons m⁻²/s⁻¹).

To put this in context, typical light conditions outside on a clear day in Europe are between 1,500-2,000 micromoles of photons m⁻²/s⁻¹ — that's more than 37,000-50,000 times the amount of light required by those Arctic microalgae. It is an amazing discovery that some plants are adapted to survive with so much less light.

This discovery offers several exciting possibilities for the field of plant sciences:

1. Extended growing seasons

Many areas around the world receive too little sunlight because they are far from the equator and endure long winters, or are persistently covered by cloud. The UK is affected by cloud cover, for instance: in 2024 it is on the way to having one of the worst periods of total light hours since the 1900s (only the 1930s and early 1990s were worse).

Now that we know how little light is required for photosynthesis, scientists could develop crops that require much less light to thrive in such places by learning from these Arctic microalgae. By unlocking their genetic potential, many crops could benefit by using plant breeding or biotech approaches to alter them accordingly.

In particular, this could help to eke more out of short growing seasons and increase food production. Even in a relatively southerly place like the UK, breeding plants that can photosynthesise with less light would potentially increase crop yields.

Related: Near-indestructible moss can survive gamma rays and liquid nitrogen

2. Sustainable agriculture

There could be additional benefits for growing plants indoors such as in greenhouses, polytunnels or vertical farms (where crops are grown in vertically stacked layers, such as racks of shelves). These systems sometimes rely on artificial lighting, which is both energy-intensive and costly.

If crops can be engineered to perform photosynthesis at lower light intensities — without compromising things like yield, taste or smell, the energy demand for artificial lighting could be reduced. This would reduce costs, a benefit that could be passed on to customers, and also help cut carbon emissions.

3. Space farming

Perhaps one of the most exciting prospects of this research is that it could potentially make it easier to grow plants in space. One of the main challenges for space missions to the Moon, Mars or eventually beyond, is how to feed anyone trying to live in those worlds for any length of time. Sunlight can be limited, so we'll need highly efficient ways of producing food that don't use much energy.

The discovery that photosynthesis can occur under such minimal light conditions suggests that crops could be grown either on other worlds or in spaceships using less energy to create light than previously thought. Combined with crops that are conducive to space conditions — spinach, lettuce and potatoes are among those that have been grown there before — this could be a critical step forward for long-term missions.

In short, this discovery is a promising breakthrough for the future. For those who sat through photosynthesis lessons in school and perhaps found it tedious, these new possibilities move it to a whole other galaxy.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

The earliest direct evidence of photosynthesis has been discovered in fossils dating back to 1.75 billion years ago.

Scientists collected fossils from Australia, Canada and the Democratic Republic of Congo and found the samples from Australia and Canada contained evidence of cyanobacteria, the oldest known lifeform on Earth. Scientists believe that cyanobacteria first emerged 2 to 3 billion years ago, before evolving to be capable of oxygen-producing, or oxygenic, photosynthesis.

In a study published Jan. 3 in the journal Nature, researchers revealed these cyanobacteria fossils featured photosynthetic structures, known as thylakoid membranes, which contain pigments like chlorophyll that convert light into chemical energy via photosynthesis.

The cyanobacteria were preserved in a mud clay that was compacted over time to become rock. The researchers used a technique called transmission electron microscopy (TEM) to see the membranes and other tiny details preserved in the fossils.

Instead of using light to image objects, TEM uses electrons, which have a much smaller wavelength than light, allowing us to see much finer details down to the atomic level. Scientists bombard a sample with an electron beam. Some electrons will pass through while some will be absorbed or scattered off more dense parts of the object. 

Related: 'Once again, innovation and proliferation ended with catastrophe': The environmental disaster of plants taking over the world

"Finding these membranes tells us that [these cells] are indeed cyanobacteria that are performing oxygenic photosynthesis," lead author Emmanuelle Javaux, a paleobiologist from the University of Liège in Belgium, told Live Science. "This pushes back the fossil record of such membranes by 1.2 billion years."

Javaux said identifying the exact time in which cyanobacteria evolved the ability to produce oxygen is an important milestone in Earth's natural history.

The concentration of oxygen in Earth's atmosphere rose dramatically around 2.45 billion years ago, in what is known as the Great Oxidation Event.

The rise in atmospheric oxygen transformed life on Earth. It unlocked aerobic respiration for many lifeforms and increased the rate at which minerals weathered and provided nutrients to different environments. 

However, scientists don't know whether the Great Oxidation Event was triggered by the evolution of oxygenic photosynthesis, or whether other ecological or geological events occurred first. 

The exact biological and physical drivers of the Great Oxidation Event are deeply debated amongst scientists. Though cyanobacterial photosynthesis is generally accepted as the key reason why oxygen concentrations increased, drivers like volcanic eruptions or a decreased level of iron in the oceans may have also played a part.

"If oxygenic photosynthesis evolved very early, but oxygen levels only accumulated in the atmosphere much later, that suggests that there are other processes at work like the burial of organic carbon," Greg Fournier, a geobiologist at the Massachusetts Institute of Technology who was not involved in the study, told Live Science. 

Fournier said that the age of the fossilized structures in the new study fits well into the bounds of current theories of when cyanobacteria with thylakoid membranes emerged. 

The researchers' use of electron microscopy potentially paves the way to reanalyze older, existing fossil samples with the same imaging technique to identify exactly when cyanobacteria first evolved thylakoid membranes.

"We could potentially time these evolutionary innovations and connect them to the history of the biosphere," Fournier said.

Name: Mangrove leaf slug (Elysia bangtawaensis)

Where it lives: Shallow pools of water in the mangrove forests and swamps of southeast Asia and Australia

What it eats: The content of tiny algal cells

Why it's awesome: In addition to looking like a starry night sky, this fabulous slug belongs to the sacoglossans, also known as the "solar-powered sea slugs" — the only known group of animals that can photosynthesize by retaining chloroplasts from algae.

Mangrove leaf slugs have seven to nine sharp teeth, which they use to puncture algal cells to then suck out the good stuff inside. That includes chloroplasts, the cellular structures plants use to transform sunlight into sugars during photosynthesis. Mangrove leaf slugs, which grow up to 2 inches (5 centimeters) long, use the chloroplasts they ingest to power themselves, enabling them to survive without food for two to three months.

Related: This sea slug can chop off its head and grow an entire new body, twice

As well as producing energy, chloroplasts tint these slugs a dark, leafy-green color. This helps mangrove leaf slugs blend into their surroundings and go unnoticed by potential predators, such as crustaceans and birds, as they lounge in shaded pools amid the mangrove trees.  

After a few months, however, the chloroplasts start to shrink and the slugs turn a yellowish color, at which point they have to replenish their photosynthetic machinery with another meal of algae. Once they have fed, the famished slugs regain their leafy-green color.

And if their photosynthetic abilities weren't weird enough, mangrove leaf slugs are simultaneous hermaphrodites, meaning each slug has the sexual organs of both sexes. To reproduce, two slugs hug tight and insert their penises into each other's vaginas at the same time. After sex, the slugs sometimes form a ball as they withdraw their penises. They then lay egg strings up to 28 inches (71 cm) long and coil them around solid features on the swampy substrate. The eggs hatch within a week, releasing a fresh batch of tiny mangrove leaf slug larvae.

 Image courtesy of Nick Volpe Wildlife Photography. 

Earth is being choked by a thick, curling fog of carbon dioxide that coats the planet as the months go by, a series of NASA videos shows. The newly released animations visualize the astonishing scale of human carbon dioxide (CO2) emissions over a year by coloring the invisible greenhouse gas.

The animations were produced by NASA's Scientific Visualization Studio and show CO2 emissions, which are cooking the planet, during the year 2021, with contributions from various human and natural sources highlighted in different colors.

In the animations, emissions from fossil fuel combustion are shown in orange, and those from burning biomass — living or dead vegetation burned to clear land for agriculture or set on fire by lightning, for example — appear in red. Carbon dioxide produced by land ecosystems through plant respiration is depicted in green, and emissions escaping from the oceans are in blue.

The model also shows where CO2 is absorbed by marine and land ecosystems, such as rainforests, via photosynthesis (in the oceans, this is done by algae). Collectively, these natural ecosystems soak up half of human emissions every year and play a vital role in mitigating climate change by periodically acting as carbon "sinks."

Related: New map of methane 'super-emitters' shows some of the largest methane clouds ever seen

"Though the land and oceans are each carbon sinks in a global sense, individual locations can be sources at different times," scientists noted in a NASA statement.

The three videos present the ebb and flow of CO2 across different regions of the world and highlight where the gas is emitted and absorbed over the course of a year.

In an animation featuring North and South America, a yellowish-brown cloud representing emissions from fossil fuels and burning biomass gradually builds in the Northern Hemisphere. Even on such a large scale, emissions can be attributed to specific regions.

"Some interesting features include fossil fuel emissions from the northeastern urban corridor that extends from Washington D.C. to Boston in the United States," scientists wrote in the statement.

Small green streaks that show emissions from land ecosystems curl in and out of this cloud during the winter months. That's because plants that absorb CO2 through photosynthesis during the growing season release much of this carbon in the wintertime, according to the statement.

The dotted green surface pulsing across South America depicts the absorption of CO2 by trees, which occurs only during the day. "The fast oscillation over the Amazon rainforest shows the impact of plants absorbing carbon while the sun is shining and then releasing it during nighttime hours," the scientists wrote in the statement.

A second animation covers parts of Asia and Australia. "The most notable feature is fossil fuel emissions from China," the statement said. Australia acts mainly as a carbon sink — as illustrated by flashing, green dots across most of the country — because the relatively sparse population emits less CO2 than its neighbors. Toward the end of the animation, the cloud of fossil fuel emissions from the Northern Hemisphere drifts southward and envelopes Australia too.

What the NASA video doesn't show is that Australia has the world's highest CO2 emissions from coal per person. 

The third video highlights Africa, Europe and the Middle East, with the vast majority of fossil fuel emissions produced in Europe and Saudi Arabia. Wispy red clouds hovering over central Africa depict emissions from fires that people light to clear leftover crops, according to the statement.

While CO2 emissions from fossil fuels are the main driver of climate change, fires contribute to global warming by reducing the amount of carbon that land ecosystems will soak up in the future, according to the statement. That's because charred soils lock up less carbon, and because fires diminish the density and size of trees. 

Light is the basis for almost all life on Earth. Using energy from the sun, plants, algae and some bacteria create complex sugar molecules that serve as the foundations for most of nature's food chains. But parts of this world-feeding chemical reaction have remained somewhat of a mystery — until now. 

For the first time, researchers have observed the beginnings of photosynthesis, starting with a single photon. 

"A huge amount of work, theoretically and experimentally, has been done around the world trying to understand what happens after the photon is absorbed. But we realized that nobody was talking about the first step," Graham Fleming, a chemist at the University of California Berkeley and co-author of the new research, said in a statement. Fleming and his team described the process in a study published June 14 in the journal Nature.

Related: Scientists accidentally discover photosynthesis doesn't work exactly like we thought it did

When light hits a plant's chloroplast — the sugar factory of the organelle world — it absorbs energy from the incoming photons and uses it to turn carbon dioxide and water into glucose and oxygen, thanks to a pigment called chlorophyll. 

Scientists have known about this process since at least the late 1700s, but it's taken much longer to unravel the granular details. A pair of French scientists first isolated chlorophyll in the early 1800s, and by the end of the century, botanist Theodor Wilhelm Engelmann had uncovered its role in absorbing sunlight, according to a 2019 paper published in the Annals of Botany. Researchers made more progress in determining the biochemistry of photosynthesis throughout the 20th century, discovering, for example, that excited electrons help to transfer energy through the chloroplasts. 

They also realized that chloroplasts must be very sensitive to light — after all, plants can photosynthesize in shady conditions, and the photons in a ray of sunshine are relatively diffuse. Scientists hypothesized that only a small number of photons are needed to kick off the process. However, nobody had successfully observed that crucial first step.

In the new study, the researchers looked at purple photosynthetic bacteria, which share an ancient ancestor with modern-day plants and algae. They set up a photon source that spits out just two photons at a time. During each test, the first photon fired out was absorbed by an ultra-sensitive detector, while the other struck the bacteria's equivalent of a chloroplast. Sure enough, when the second photon hit its target, photosynthesis started up.

The researchers performed this test over 1.5 million times to ensure that the second photon, rather than some outside force, was triggering the chemical reaction. This confirmed that just one photon was enough to set off photosynthesis. 

"This experiment has shown that you can actually do things with individual photons. So that's a very, very important point," Birgitta Whaley, a chemical physicist at UC Berkeley and co-author of the study, said in a statement. 

One of the most well-studied chemical processes in nature, photosynthesis, may not work quite how we thought it did, scientists have accidentally discovered.

Photosynthesis is the process by which plants, algae and some bacteria convert carbon dioxide and water into oxygen and sugars to use as energy. To do this, the organisms use sunlight to oxidize, or take electrons from, water; and reduce, or give electrons to, carbon dioxide molecules. These chemical reactions require photosystems — protein complexes that contain chlorophyll, a pigment that absorbs light and gives plant leaves and algae their green color — to transfer electrons between different molecules.

In the new study, published March 22 in the journal Nature, researchers used a new technique, known as ultrafast transient absorption spectroscopy, to study how photosynthesis works at a timescale of one quadrillionth of a second (0.000000000000001 second) for the first time. The team was initially trying to figure out how quinones — ring-shaped molecules that can steal electrons during chemical processes — impact photosynthesis. But instead, the researchers found that electrons could be released from photosystems much earlier during photosynthesis than scientists previously believed was possible.

"We thought we were just using a new technique to confirm what we already knew," study co-author Jenny Zhang, a biochemist specializing in photosynthesis at the University of Cambridge in England, said in a statement. "Instead, we found a whole new pathway, and opened the black box of photosynthesis a bit further."

Related: New 'artificial' photosynthesis is 10x more efficient than previous attempts 

Two photosystems are used during photosynthesis: photosystem I (PSI) and photosystem II (PSII). PSII primarily provide electrons to PSI by taking them from water molecules: PSI then further excites the electrons before releasing them to eventually be given to carbon dioxide to create sugars, via a series of complex steps. 

Past research had suggested that the protein scaffolding in PSI and PSII was very thick, which helped to contain electrons within them before being passed on to where they were needed. But the new ultrafast spectroscopy technique revealed that the protein scaffolding was more "leaky" than expected and that some electrons could escape from the photosystems almost immediately after light was absorbed by the chlorophyll within the photosystems. These electrons could therefore reach their destinations faster than expected.

"The new electron transfer pathway we found here is completely surprising," Zhang said. "We didn't know as much about photosynthesis as we thought we did."

The electron leaking was observed in both isolated photosystems and within "living" photosystems inside cyanobacteria.

In addition to rewriting what we know about photosynthesis, the discovery opens up new avenues for future research and biotechnology applications. The team believes that by "hacking" photosynthesis to release more of these electrons at earlier stages, the process could become much more efficient, which could help produce plants that are more resistant to sunlight or be replicated artificially to create renewable energy sources to help combat climate change, according to the statement. However, much more research is needed before this can happen.

"Many scientists have tried to extract electrons from an earlier point in photosynthesis, but said it wasn't possible because the energy is so buried in the protein scaffold," Zhang said. "The fact that we can [potentially] steal them at an earlier process is mind-blowing."

Logic-defying phytoplankton blooms have been discovered lurking beneath the ocean's surface in both of Earth's polar regions, two unrelated new studies have revealed. The highly unlikely "bottom blooms," which grow near the seafloor in the Arctic and below sea ice in Antarctica, could support hidden ecosystems that scientists know nothing about.

Phytoplankton are tiny photosynthetic algae that account for around half of the primary production — the conversion of sunlight to organically available energy — in Earth's oceans and help to prop up the marine food web. Phytoplankton blooms, which are often visible from space as beautiful green swirls on the ocean's surface, occur when the algae rapidly reproduce due to an overabundance of available nutrients. However, phytoplankton also require sunlight, which limits blooms to the upper layer of the ocean, where sunlight is strongest.   

The Arctic and Antarctica are home to some of the most nutrient-rich waters in the world and support massive phytoplankton blooms during their respective summer months, when sea ice is at its minimum extent and sunlight can reach more of the ocean's surface. But as sea ice builds up in the wintertime, the blooms lose access to sunlight and start to die.

However, a pair of new studies published by two different research teams has revealed that some of these blooms are either surviving in deeper waters after the sea ice thickens, as is the case in the Arctic, or starting to bloom beneath the sea ice before it begins its seasonal melt, as seen in Antarctica. 

Related: Discovery of 'hidden world' under Antarctic ice has scientists 'jumping for joy' 

Both studies suggest that climate change may be playing a key role in the emergence of these bottom blooms, by thinning out sea ice, increasing the amount of time the oceans are ice-free and increasing the amount of sunlight that reaches deeper waters. 

Arctic blooms 

In 2016, a scientific expedition conducting routine samples of the Arctic water column in the Chukchi Sea, between Siberia and Alaska, found an abundance of phytoplankton in waters near the seafloor. Normally, phytoplankton that have sunk down to this depth have either died or become almost completely inactive, but these algae were still photosynthesizing at a normal rate, which suggested that they could still be blooming. 

After the discovery of this potential bottom bloom, Takuhei Shiozaki, a member of the expedition and a microbial oceanographer at the University of Tokyo, returned with a new team of researchers to take more samples. They later carried out a series of laboratory experiments to see how the algae were able to survive at this depth. 

The results, which were published Sept. 27 in the journal Global Change Biology, revealed that the bottom-dwelling phytoplankton were able to survive even when the light was only 1% as strong as it was at surface levels. The researchers suspect that because sea ice is forming later in the year as a result of climate change, the phytoplankton that sink to the seafloor still receive enough light to continue blooming. 

However, more samples from the Arctic are required to understand the full extent of bottom blooms in the region.

"We still don't know the total production and the amount of phytoplankton 'seed' on the seafloor that [could] be the origin of a bottom-associated bloom," Shiozaki told the American Geophysical Union's magazine, Eos. 

Antarctic blooms 

More recently, a study published Nov. 17 in the journal Frontiers in Marine Science revealed that phytoplankton can also bloom beneath Antarctic sea ice. 

Scientists had previously thought that Antarctic sea ice — much like ice in the Arctic — would be too thick to allow enough light through to sustain an algal bloom. But after hearing about some of the preliminary results from the Arctic study, a separate team of researchers suspected that the algae in Antarctica also might be able to bloom beneath sea ice before the ice began to melt in the summer.

The team used deep-diving floats to measure the amount of chlorophyll-a, the pigment used by algae and other plants during photosynthesis, in the water. They also measured how much light scattered through the water column, which is another indicator of phytoplankton.

Related: Enormous river discovered beneath Antarctica is nearly 300 miles long

"We found that nearly all examples of floats profiling under Antarctic sea ice record increases in phytoplankton before sea ice retreats," study lead author Christopher Horvat, a mathematical oceanographer at Brown University in Rhode Island, said in a statement. "In many cases, we observed significant blooms."

The researchers are confident that these types of blooms are widespread in the region. "We found that 50% or more of the under-ice Antarctic might support under-ice blooms," Horvat said. 

Hidden ecosystems 

Phytoplankton form the foundation of the marine food web, so if they can bloom in areas where scientists previously assumed they could not, there may be other unknown populations of marine organisms in these areas possibly feeding off them.

"Higher trophic levels migrate to where the productivity is, and if it is under the ice, one might expect the food web follows," Horvat said, adding that more research is needed to tell for sure.

Bottom blooms could also play a key role in the local carbon cycle, because phytoplankton absorb carbon from the water during photosynthesis.

"Investigations of the carbon sequestration capacity of the Arctic Ocean have [so far] focused on surface processes," Shiozaki said. "However, assuming that carbon is actively fixed by phytoplankton in the subsurface, this process should be taken into account [as well]."

A new method of artificial photosynthesis could get humans one step closer to using the machinery of plants to make fuels. 

The new system is 10 times more efficient than previous synthetic photosynthesis methods. While natural photosynthesis allows plants to turn carbon dioxide (CO2) and water into carbohydrates using the power of the sun, the artificial method can turn carbon dioxide and water into energy-dense fuels like methane and ethanol. This could provide an alternative to fossil fuels drilled out of ancient rock. 

"The biggest challenge many people don’t realize is that even nature has no solution for the amount of energy we use,"  University of Chicago chemist Wenbin Lin, one of the authors of the new study, said in a statement. Natural photosynthesis, while sufficient for plants to feed themselves, falls short of providing the quantity of energy required to fuel our homes, cities and nations. "We will have to do better than nature, and that’s scary," he said.

Researchers have been working to borrow the machinery of photosynthesis to create their own desired chemicals for years, but tweaking photosynthesis to serve human needs is not easy. The process is complicated and involves two steps: First, breaking apart water and CO2, and second, reconnecting the atoms into carbohydrates. Lin and his team had to create a system that would instead produce methane, or CH4, which is a carbon surrounded by four hydrogen molecules. 

Though combusting this synthetic methane would still lead to greenhouse gas emissions, researchers are also working on using artificial photosynthesis to make hydrogen fuels, which release only water vapor and warm air.

Related: Effects of global warming

To do this, they began with a metal-organic framework — a web made of charged metal atoms linked by organic molecules. (Organic molecules contain carbon.) They submerged single layers of this metal-organic framework in a cobalt solution; this element is good at picking up electrons and moving them around during chemical reactions. 

Then the researchers did something that hadn't been tried before. They added amino acids, the molecular building blocks of proteins, to the mix. These amino acids boosted the efficiency of both sides of the reaction, breaking down CO2 and water and rebuilding them as methane. The resulting system was 10 times more efficient than previous artificial photosynthesis methods, the team reported in the journal Nature Catalysis on Nov. 10. 

However, that's still not efficient enough to make enough methane for human fuel use. 

"Where we are now, it would need to scale up by many orders of magnitude to make a sufficient amount of methane for our consumption," Lin said. But, he said, the team was able to determine how the system works on a molecular level, which had never been fully understood before. Understanding the process is a crucial step before they can scale up the process. 

If the system isn't currently efficient enough to fuel cars or heat homes, it may already be feasible for other uses that don't require such a high volume of product. For example, Lin said, a similar method could be used to produce basic chemicals for pharmaceuticals. 

"So many of these fundamental processes are the same,” said Lin. "If you develop good chemistries, they can be plugged into many systems." 

Layered rocks in Western Australia are some of Earth's earliest known life, according to a new study. 

The fossils in question are stromatolites, layered rocks that are formed by the excretions of photosynthetic microbes. The oldest stromatolites that scientists agree were made by living organisms date back 3.43 billion years, but there are older specimens, too. In the Dresser Formation of Western Australia, stromatolites dating back 3.48 billion years have been found. 

However, billions of years have wiped away traces of organic matter in these older stromatolites, raising questions about whether they were really formed by microbes or whether they might have been made by other geological processes. 

The new study's verdict: It was ancient life. 

"We were able to find certain specific microstructures within particular layers of these rocks that are strongly indicative of biological processes," said Keyron Hickman-Lewis, a paleontologist at the Natural History Museum in London, who led the research. 

Related: Oldest animal life on Earth possibly discovered. And it’s related to your bath sponge. 

Microbial mats 

The findings could have implications for the search for life on Mars, Hickman-Lewis told Live Science. The stromatolites in the Dresser Formation are encrusted in iron oxide from the reaction of iron with oxygen in the atmosphere. Mars' surface is similarly oxidized — thus the rusty orange color — but its rocks could hold similar structures left behind by ancient Martian life, Hickman-Lewis said. 

Hickman-Lewis and his team examined Western Australian stromatolites first discovered in 2000 by study co-author Frances Westall at the National Center for Scientific Research (CNRS) in France. They used a variety of high-resolution 2D and 3D imaging techniques in order to peer into the layers of the stromatolite at a fine scale. 

What they saw hinted at biological growth in all its messy glory. The researchers observed uneven layers, including little dome shapes that are indicative of photosynthesis, since microbes with the most access to the sun will grow more vigorously than those not as high in the structure. They also saw columnar structures that are typical in modern stromatolites, which are still found in a few locations around the globe. 

"Microbial mats give you layers that are uneven in their thickness and tend to be wrinkly or crinkly or go up and down on very small spatial scales," said Linda Kah, a sedimentologist and geochemist at the University of Tennessee who was not involved in the new study. Putting all the structural clues together, she told Live Science, "you end up with what looks like the characteristics of a microbial mat."  

Martian microbes? 

The evidence that the Dresser Formation stromatolites are signs of ancient life doesn't make them the oldest life on the planet. That (possible) honor may go to stromatolites found in 3.7 billion-year-old rock in Greenland, or possibly to microfossils from Canada that might be as old as 4.29 billion years. It's very difficult to distinguish biological life from non-organic processes in these very old rocks, however, so these finds and others from a similar timeframe are controversial.  

Based on the minerals in the stromatolites, the Western Australia microbial mats probably formed in a shallow lagoon fed by hydrothermal vents that was also connected to the ocean, the researchers reported Nov. 4 in the journal Geology.

The techniques used to study the Western Australian stromatolites could be useful for seeking life on Mars, Hickman-Lewis said, especially if Mars samples can be returned to Earth. 

Scientists should "consider some of the analyses here as a trial run of the analyses we will have to do in around a decade's time when we have materials from Mars." 

Photosynthesis is the process used by plants, algae and some bacteria to turn sunlight into energy. The process chemically converts carbon dioxide (CO2) and water into food (sugars) and oxygen. The chemical reaction often relies on a pigment called chlorophyll, which gives plants their green color.  Photosynthesis is also the reason our planet is blanketed in an oxygen-rich atmosphere.

Types of photosynthetic processes

There are two types of photosynthesis: oxygenic and anoxygenic. They both follow very similar principles, but the former is the most common and is seen in plants, algae and cyanobacteria. 

During oxygenic photosynthesis, light energy transfers electrons from water (H2O) taken up by plant roots to CO2 to produce carbohydrates. In this transfer, the CO2 is "reduced," or receives electrons, and the water is "oxidized," or loses electrons. Oxygen is produced along with carbohydrates.

This process creates a balance on Earth, in which the carbon dioxide produced by breathing organisms as they consume oxygen in respiration is converted back into oxygen by plants, algae and bacteria.

Anoxygenic photosynthesis, meanwhile, uses electron donors that are not water and the process does not generate oxygen, according to "Anoxygenic Photosynthetic Bacteria" by LibreTexts. The process typically occurs in bacteria such as green sulfur bacteria and phototrophic purple bacteria. 

The Photosynthesis equation

Though both types of photosynthesis are complex, multistep affairs, the overall process can be neatly summarized as a chemical equation.

The oxygenic photosynthesis equation is: 

6CO2 + 12H2O + Light Energy → C6H12O6 + 6O2 + 6H2O

Here, six molecules of carbon dioxide (CO2) combine with 12 molecules of water (H2O) using light energy. The end result is the formation of a single carbohydrate molecule (C6H12O6, or glucose) along with six molecules each of oxygen and water.

Similarly, the various anoxygenic photosynthesis reactions can be represented as a single generalized formula:

CO2 + 2H2A + Light Energy → [CH2O] + 2A + H2O

The letter A in the equation is a variable, and H2A represents the potential electron donor. For example, "A" may represent sulfur in the electron donor hydrogen sulfide (H2S), according to medical and life sciences news site News Medical Life Sciences. 

How is carbon dioxide and oxygen exchanged?

Plants absorb CO2 from the surrounding air and release water and oxygen via microscopic pores on their leaves called stomata. 

When stomata open, they let in CO2; however, while open, the stomata release oxygen and let water vapor escape. Stomata close to prevent water loss, but that means the plant can no longer gain CO2 for photosynthesis. This tradeoff between CO2 gain and water loss is a particular problem for plants growing in hot, dry environments. 

How do plants absorb sunlight for photosynthesis?

Plants contain special pigments that absorb the light energy needed for photosynthesis.

Chlorophyll is the primary pigment used for photosynthesis and gives plants their green color, according to science education site Nature Education. Chlorophyll absorbs red and blue light and reflects green light. Chlorophyll is a large molecule and takes a lot of resources to make; as such, it breaks down towards the end of the leaf's life, and most of the pigment's nitrogen (one of the building blocks of chlorophyll) is resorbed back into the plant,  When leaves lose their chlorophyll in the fall, other leaf pigments such as carotenoids and anthocyanins begin to show. While carotenoids primarily absorb blue light and reflect yellow, anthocyanins absorb blue-green light and reflect red light, according to Harvard University's The Harvard Forest.

Related: What if humans had photosynthetic skin?

Pigment molecules are associated with proteins, which allow them the flexibility to move toward light and toward one another. A large collection of 100 to 5,000 pigment molecules constitutes an "antenna," according to an article by Wim Vermaas, a professor at Arizona State University. These structures effectively capture light energy from the sun, in the form of photons.

The situation is a little different for bacteria. While cyanobacteria contain chlorophyll, other bacteria, for example, purple bacteria and green sulfur bacteria, contain bacteriochlorophyll to absorb light for anoxygenic photosynthesis, according to "Microbiology for Dummies" (For Dummies, 2019). 

How does photosynthesis start?

It was previously hypothesized that just a small number of photons would be needed to kickstart photosynthesis, but researchers never successfully observed this first step. However, in 2023, scientists discovered that photosynthesis appears to begin with a single photon. 

The researchers set up an experiment where a photon source spat out two photons at a time. One was absorbed by a detector, while the other hit a bacteria's chloroplast equivalent. When the second photon hit, photosynthesis began. 

After performing the test over 1.5 million times, the researchers confirmed that just one photon is needed to start photosynthesis.

Where in the plant does photosynthesis take place?

Photosynthesis occurs in chloroplasts, a type of plastid (an organelle with a membrane) that contains chlorophyll and is primarily found in plant leaves. 

Chloroplasts are similar to mitochondria, the energy powerhouses of cells, in that they have their own genome, or collection of genes, contained within circular DNA. These genes encode proteins that are essential to the organelle and to photosynthesis.

Inside chloroplasts are plate-shaped structures called thylakoids that are responsible for harvesting photons of light for photosynthesis, according to the biology terminology website Biology Online. The thylakoids are stacked on top of each other in columns known as grana. In between the grana is the stroma — a fluid containing enzymes, molecules and ions, where sugar formation takes place. 

Ultimately, light energy must be transferred to a pigment-protein complex that can convert it to chemical energy, in the form of electrons. In plants, light energy is transferred to chlorophyll pigments. The conversion to chemical energy is accomplished when a chlorophyll pigment expels an electron, which can then move on to an appropriate recipient. 

The pigments and proteins that convert light energy to chemical energy and begin the process of electron transfer are known as reaction centers.

Light-dependent reactions

When a photon of light hits the reaction center, a pigment molecule such as chlorophyll releases an electron.

The released electron escapes  through a series of protein complexes linked together, known as an electron transport chain. As it moves through the chain, it generates the energy to produce ATP (adenosine triphosphate, a source of chemical energy for cells) and NADPH — both of which are required in the next stage of photosynthesis in the Calvin cycle. The "electron hole" in the original chlorophyll pigment is filled by taking an electron from water. This splitting of water molecules releases oxygen into the atmosphere.

Light-independent reactions: The Calvin cycle

The Calvin cycle is the three-step process that generates sugars for the plant, and is named after Melvin Calvin, the Nobel Prize-winning scientist who discovered it decades ago. The Calvin cycle uses the ATP and NADPH produced in chlorophyll to generate carbohydrates. It takes plate in the plant stroma, the inner space in chloroplasts.

In the first step of this cycle, called carbon fixation, an enzyme called RuBP carboxylase/oxygenase, also known as rubiso, helps incorporate CO2 into an organic molecule called 3-phosphoglyceric acid (3-PGA). In the process, it breaks off a phosphate group on six ATP molecules to convert them to ADP, releasing energy in the process, according to LibreTexts.

In the second step, 3-PGA is reduced, meaning it takes electrons from six NADPH molecules and produces two glyceraldehyde 3-phosphate (G3P) molecules.

One of these G3P molecules leaves the Calvin cycle to do other things in the plant. The remaining G3P molecules go into the third step, which is regenerating rubisco. In between these steps, the plant produces glucose, or sugar.

Three CO2 molecules are needed to produce six G3P molecules, and it takes six turns around the Calvin cycle to make one molecule of carbohydrate, according to educational website Khan Academy.

Types of photosynthesis

There are three main types of photosynthetic pathways: C3, C4 and CAM. They all produce sugars from CO2 using the Calvin cycle, but each pathway is slightly different.

C3 photosynthesis

Most plants use C3 photosynthesis, according to the photosynthesis research project Realizing Increased Photosynthetic Efficiency (RIPE). C3 plants include cereals (wheat and rice), cotton, potatoes and soybeans. This process is named for the three-carbon compound 3-PGA that it uses during the Calvin cycle. 

C4 photosynthesis

Plants such as maize and sugarcane use C4 photosynthesis. This process uses a four-carbon compound intermediate (called oxaloacetate) which is converted to malate, according to Biology Online. Malate is then transported into the bundle sheath where it breaks down and releases CO2, which is then fixed by rubisco and made into sugars in the Calvin cycle (just like C3 photosynthesis). C4 plants are better adapted to hot, dry environments and can continue to fix carbon even when their stomata are closed (as they have a clever storage solution), according to Biology Online. 

CAM photosynthesis

Crassulacean acid metabolism (CAM) is found in plants adapted to very hot and dry environments, such as cacti and pineapples, according to the Khan Academy. When stomata open to take in CO2, they risk losing water to the external environment. Because of this, plants in very arid and hot environments have adapted. One adaptation is CAM, whereby plants open stomata at night (when temperatures are lower and water loss is less of a risk). According to the Khan Academy, CO2 enters the plants via the stomata and is fixed into oxaloacetate and converted into malate or another organic acid (like in the C4 pathway). The CO2 is then available for light-dependent reactions in the daytime, and stomata close, reducing the risk of water loss. 

Additional resources

Discover more facts about photosynthesis with the educational science website sciencing.com. Explore how leaf structure affects photosynthesis with The University of Arizona. Learn about the different ways photosynthesis can be measured with the educational science website Science & Plants for Schools.  

This article was updated by Live Science managing editor Tia Ghose on Nov. 3, 2022.

Powerful earthquakes that shook Earth some 3.8 billion years ago split open the planet's crust and allowed chemical reactions to unfold deep within the fractured rock. These reactions, fueled by seismic activity, water and near-boiling temperatures, may have provided oxygen to some of the world's earliest life forms, a new study suggests. 

This oxygen would have come packaged in the compound hydrogen peroxide (H2O2), which contains two hydrogen atoms and two oxygen atoms bound together, according to the study, published Monday (Aug. 8) in the journal Nature Communications. Perhaps best known as an antiseptic, hydrogen peroxide can, of course, be toxic to living organisms, but it can still be a useful oxygen source once broken down by enzymes or by reactions that occur under high heat, Jon Telling, the study's senior author and a senior lecturer in geochemistry and geomicrobiology at Newcastle University in the U.K., told Live Science. 

Now, in laboratory experiments, Telling and his colleagues have uncovered a way that ample amounts of hydrogen peroxide may have formed on early Earth and thus served as a potential oxygen source for some of the planet's earliest organisms. These reactions occur most efficiently at temperatures near the boiling point of water — 212 degrees Fahrenheit, or 100 degrees Celsius — but still produce a little H2O2 at temperatures below 176 F (80 C), the researchers found. 

Notably, these temperatures overlap with the temperature range that thermophiles and hyperthermophiles — meaning heat-loving bacteria and archaea — are known to thrive in, Telling said. It's thought that the common ancestor of all life on Earth also evolved to live in scorching hot environments, and so in theory, this mysterious ancestral organism may have been influenced by the presence of hydrogen peroxide forged deep in the planet's crust. 

Related: Earth nearly lost all its oxygen 2.3 billion years ago

And importantly, because hydrogen peroxide can damage the fats, proteins and DNA of cells, early organisms would have needed strategies to "detoxify" the compound if it was present in their environment, said Lynn Rothschild, a senior research scientist at the NASA Ames Research Center in California, who was not involved in the new study. Hydrogen peroxide is also a natural byproduct of photosynthesis, so to evolve the ability to photosynthesize, organisms likely needed to be able to deal with H2O2, first. 

"There had to be sources of reactive oxygen species" — including hydrogen peroxide — "on early Earth before the advent of oxygenic photosynthesis," Rothschild told Live Science.

Deep inside the crust 

Previous studies, including work led by Rothschild's lab, suggested that minerals thought to exist in early Earth's crust could be a potential source of hydrogen peroxide, and thus, a potential source of oxygen. 

Some of these experiments involved pulverizing rocks under specific conditions and then exposing those crushed rocks to water. This series of events mimics, on a small scale, the physical stress rocks endured in tectonically active regions of early Earth's crust, where the crust cracked open and water could then seep inside. When Earth was less than a billion years old, the planet did not yet have large slabs of crust sliding over its mantle, as tectonic plates move across the world today, Telling said. However, at that time, the crust still buckled and cracked in localized regions due to volcanic activity and interactions between far smaller chunks of crust, he said. 

Although past experiments demonstrated that this early tectonic activity could potentially produce hydrogen gas (a component of hydrogen peroxide) and fully-formed hydrogen peroxide, these studies only generated small amounts of these compounds. In their new study, Telling and his colleagues ran similar experiments but exposed the crushed rocks to a wider range of temperatures and for longer periods of time — up to a week. Based on the past studies, they suspected that this approach might boost the amount of hydrogen peroxide produced.

In their rock-crushing experiments, the team used granite, a rock found in continental crust, and basalt and peridotite, which would have been abundant in early Earth's oceanic crust. They ground these rocks to fine powder in oxygen-free containers, carefully transferred the crushed rock to airtight bottles, added water and then cranked up the heat. 

Related: Earth's 1st continents arose hundreds of millions of years earlier than thought

As the rock powders reached near-boiling temperatures, "defects" within their component minerals grew less stable and more likely to react with water. Specifically, these defects included "peroxy linkages," or places where two oxygen atoms are bound together within the minerals' crystal structure, where usually oxygen would only bind to the element silicon. Such defects can be introduced into a crystal if water is inadvertently added to its structure as it forms, Telling said. 

"When these rocks containing these peroxy linkages are put under stress, these defects can actually kind of dislocate," he explained. "They can move through the crystal structure to the surfaces where they can then start to interact with water," and this interaction ultimately makes hydrogen peroxide. 

These results suggest that, at least in regions of early Earth rocked by quakes and baked at high temperatures, hydrogen peroxide may have been a common feature of the environment. That said, the experiments can't capture the exact rate or scale at which these H2O2-producing reactions took place on early Earth, Telling noted.

"It would be interesting to see how widespread this phenomenon is" and how hydrogen peroxide influenced the evolution of early organisms, on a global scale, said Rothschild, who studies how life may have originated and evolved on early Earth and potentially elsewhere in the galaxy. That said, H2O2 wouldn't have needed to be present in all environments on early Earth to hold sway over the evolution of life on the planet. If you're a tiny microbe that measures mere microns across, you're only influenced by the chemicals in your immediate surroundings, anyway. 

"Honestly, it's good enough if you have reactive oxygen species in your neighborhood," Rothschild said. This early exposure to environmental H2O2 may have provided essential "training" for the organisms that evolved into cyanobacteria, the blue-green algae responsible for pumping Earth's atmosphere full of oxygen and thus shaping the course of our planet's history, she said. 

Originally published on Live Science.

As soon as the weather warms, lawn mowers also begin to start up (at least in suburbia), creating those perfectly shaped and brilliantly green lawns. But why is grass green and not blue or purple, say?

The short answer is a green pigment called chlorophyll. The longer answer has to do with wavelengths and cellular components called organelles and photosynthesis, which plants use to make food from sunlight.

Tucked inside tiny organelles called chloroplasts are molecules of chlorophyll. A molecule of chlorophyll consists of a magnesium ion at its center that is bonded to a porphyrin, which is a large organic nitrogen molecule, according to WebExhibits, an online museum of science, humanities and culture. 

Chlorophyll gets its name from the Greek word "chloros," which means "yellowish-green," according to WebExhibits. But how does it make your freshly cut lawn appear a gorgeous green? The molecule absorbs certain wavelengths of visible light, primarily red (a long wavelength) and blue, a shorter wavelength. The green region of the electromagnetic spectrum doesn't get absorbed and instead is reflected, right to your eyes. And voilà — you have green grass.

Related: Do trees exist (scientifically speaking)?

Chlorophyll does more than paint your lawn a verdant hue. It's important for photosynthesis, in which a plant uses the sun's energy to turn carbon dioxide and water into food (in the form of sugars) for growth.

This sugar-making process takes place inside chloroplasts (the same teensy spots where chlorophyll resides). Inside these structures, chlorophyll (and to a lesser extent other pigments) absorb the sun's light and transfer the energy from that light to two energy-storing molecules, National Geographic reported. The plant then uses that energy to turn the CO2 and water into sugars. In combination with nutrients in the soil, for instance, plants can use those sugars to build more green plant parts.

Originally published on Live Science. 

Here's a new spin on how Earth became an oxygen-rich planet: As our planet's rotation slowed, microbes were bathed in longer stints of sunlight that revved up their release of oxygen into the atmosphere.

Every breath you take is possible because billions of years ago, dense mats of cyanobacteria — the first life on Earth — began churning out oxygen as a byproduct from photosynthesis. But scientists still didn't know for sure what triggered two transformative oxygenation events that turned Earth from a low-oxygen planet into an oxygen-rich world where complex organisms could evolve and diversify. 

Now, researchers have identified an important factor that could have spurred the release of microbial-generated oxygen: slowdowns in Earth's rotation beginning about 2.4 billion years ago. Earth spun more quickly when it was a newborn planet, completing a turn in just a handful of hours, but it gradually decelerated over hundreds of millions of years. Once the length of a day reached a certain threshold — possibly during those key oxygenation periods — longer stretches of sunlight may have enabled more oxygen molecules to hop from areas of high concentration (inside the bacteria mats) to areas of lower concentration (the atmosphere), according to a new study.

Related: Earth's 8 biggest mysteries

Scientists recently found clues to this link in a sinkhole at the bottom of Lake Huron. Bordered by Michigan in the United States and by Ontario in Canada, Lake Huron is one of the biggest freshwater lakes in the world. The lake's Middle Island Sinkhole measures 300 feet (91 meters) in diameter and lies about 80 feet (24 m) below the surface. There, sulfur-rich water nourishes colorful microbes that thrive in a low-oxygen environment, much like Earth's earliest forms of bacteria did.

In the sinkhole's chilly depths live two types of microbes: sunlight-seeking purple cyanobacteria, which produce oxygen through photosynthesis, and white bacteria, which consume sulfur and instead release sulfate. The microbes jockey for position throughout the day, with the sulfur-eating bacteria covering their purple neighbors in the morning and evening hours, blocking the purple microbes' access to the sun. However, when daylight is strongest, the white microbes shun the light and migrate deeper into the sinkhole, leaving the purple cyanobacteria uncovered and thereby able to photosynthesize and release oxygen.

There might have been similar competitions between communities of microbes billions of years ago, with oxygen-producing bacteria's sunlight exposure hampered by their microbial neighbors, the researchers wrote in the study. Then, as days on Earth became longer, the oxygen-makers gained more time in the sunlight — and released more oxygen into the atmosphere.

"We realized that there is a fundamental link between light dynamics and release of oxygen, and that link is grounded in the physics of molecular diffusion," when thermal changes cause molecules to migrate from areas of higher concentration to lower ones, said study lead author Judith Klatt, a research scientist with the Max Planck Institute for Marine Microbiology in Bremen, Germany.

"A shorter day would allow less oxygen to escape a mat, even if the same amount of oxygen is produced per hour," Klatt told Live Science in an email.

Spin cycle

Now, Earth completes a full rotation on its axis once every 24 hours, but more than 4 billion years ago, a day lasted only about six hours, the researchers reported. Over billions of years, Earth's ongoing dance with the moon has slowed the planet's rotation through a process known as tidal friction. As Earth rotates, the pull of the moon (and the sun, to a lesser extent) attracts Earth's oceans. This stretches the seas so that they bulge away from Earth's center, siphoning energy away from the spin and slowing it down, said study co-author Brian Arbic, a professor in the Earth and Environmental Sciences department at the University of Michigan's College of Literature, Science and the Arts. 

This deceleration is small, but it added up to hours of additional daylight over hundreds of millions of years; and the slowdown is still going on today, Arbic told Live Science in an email.

"Tidal friction continues to slow down the rotation rate — the days will continue to lengthen over geological time," Arbic said.

Breath of fresh air

The researchers modeled scenarios that varied day length and oxygen escape from microbial mats. When they compared their models with an analysis of the competing microbial mats sampled from the Middle Island Sinkhole, they found confirmation of their predictions: Photosynthesizing bacteria released more oxygen when days were longer.

This wasn't because the microbes photosynthesized more; rather, it was because longer periods of sunlight meant that more oxygen escaped from the mats in a single day, said study co-author Arjun Chennu, a research scientist at the Leibniz Centre for Tropical Marine Research in Bremen.

"This subtle uncoupling of oxygen release from sunlight is at the heart of the mechanism," Chennu said in a statement.

Earth's atmosphere took shape after the planet formed and cooled, around 4.6 billion years ago, and was mostly made of hydrogen sulfide, methane and carbon dioxide (CO2) — as much as 200 times the amount of CO2 as there is in the atmosphere today, according to the Smithsonian Environmental Research Center. 

That all changed following the Great Oxidation Event (GOE) about 2.4 billion years ago, followed by the Neoproterozoic Oxygenation Event about 2 billion years later, bringing atmospheric oxygen up to the present-day level of about 21%. Those two oxygenation events have previously been linked to the activity of photosynthesizing cyanobacteria, and this new evidence suggests that another factor could have been daytime on Earth — "a previously largely unconsidered factor" — becoming long enough to trigger the release of even more oxygen from microbial mats, working "in parallel with the other previously suggested drivers of oxygenation," Klatt said.

The findings were published on Aug. 2 in the journal Nature Geoscience.

Originally published on Live Science.

Two species of sea slugs can pop off their heads and regrow their entire bodies from the noggin down, scientists in Japan recently discovered. This incredible feat of regeneration can be achieved in just a couple of weeks and is absolutely mind-blowing.

Most cases of animal regeneration — replacing damaged or lost body parts with an identical replacement — occur when arms, legs or tails are lost to predators and must be regrown. But these sea slugs, which belong to a group called sacoglossans, can take it to the next level by regrowing an entirely new body from just their heads, which they seem to be able to detach from their original bodies on purpose. 

If that wasn't strange enough, the slugs' heads can survive autonomously for weeks thanks in part to their unusual ability to photosynthesize like plants, which they hijack from the algae they eat. And if that's still not enough in the bizarro realm, the original decapitated body can also go on living for days or even months without their heads.

Related: 11 body parts grown in the lab

"We believe that this is the most extreme form of autonomy and regeneration in nature," lead author Sayaka Mitoh, a doctoral student at Nara Women's University in Japan, told Live Science.

Further investigations revealed that another species of sacoglossan sea slug (Elysia atroviridis) also undergoes this type of regeneration and that certain individuals can pull off the trick more than once. 

How to grow a brand-new body 

Mitoh first stumbled across this bizarre behavior by accident when she spotted the detached head of a sacoglossan sea slug (Elysia cf. marginata) circling its detached body in a tank at the Yusa Lab at Nara Women's University in 2018. 

"One day, I found an individual of Elysia cf. marginata with its head and its body separated," Mitoh said. "I thought the poor slug would die soon." 

But instead of dying, the wound at the back of the slug's head quickly healed and was replaced by the beginnings of an entirely new body.

"After a few days, the head started regenerating the body and I could see [the] beating of the heart. It was unbelievable," Mitoh told Live Science. "I was really happy and relieved when I found it could regenerate the body."

After around three weeks, the slug had finished its body-swapping stunt and replaced the 80% of its body it had originally lost, including all the vital organs it had been able to live without for so long, according to Mitoh.

The slug's brand-new body was a perfect replica of the original, which researchers found was also doing reasonably well on it's own.

"The [original] body continues to move and live for days to months," Mitoh said. "You can see the heart beating" inside them, she added. However, the decapitated bodies did not appear to be capable of growing new heads themselves.

Exactly how the slugs regenerate their bodies from the head down is still unknown, but the researchers suspect stem cells — special undifferentiated cells that have the potential to be turned into any type of cell — play an important role.

"We think that some multipotent [stem] cells may be involved in the regeneration process," Mitoh said. In the future, she and her team hope to "further explore the mechanisms underlying this phenomenon at the tissue and cellular levels," she added.

A young slug's game 

The scientists are also not sure how the sea slugs sever their heads from their bodies in the first place or why they would want to, especially when there is no visible reason to discard their old bodies and start again.

A leading theory is that the slugs do it to remove internal parasites that have infested their old bodies. However, it may also just be a way to survive attacks from predators by sacrificing their bodies and escaping as autonomous heads and could have been triggered by something else in the lab, Mitoh said.

However, the researchers found that only the younger slugs are capable of autonomy and regeneration. When older slugs had their heads removed, the heads survived for up to 10 days but they never started eating and did not start to regenerate before dying.

"We think that very old ones gain little merit from autotomy, as they probably cannot reproduce," Mitoh said.

Although one individual in the study underwent autonomy and regeneration twice, the researchers suspect that this is probably the limit and that after a certain stage in their lives the slugs probably lose the ability altogether.

You are what you eat 

The regeneration process requires a lot of energy, which is challenging for an autonomous head to acquire, Mitoh said. 

However, the sacoglossans have a secret weapon: These particular slugs are capable of kleptoplasty, or the ability to steal chloroplasts — the parts of a cell that allow plants to convert sunlight into energy via photosynthesis — from the algae they eat and use them in their own tissues. This allows the slugs to photosynthesize, which gives them enough energy to start the regeneration process.

 "They rely on photosynthesis just after autotomy and when food is scarce," Mitoh said. "But the stolen chloroplasts last only for several days for these sea slug species, and so they probably need to eat to complete regeneration."

Mitoh and her colleagues will look for other species of sacoglossan that can regenerate in this way.

"Sacoglossan sea slugs are well known for their ability for kleptoplasty, and we now learned that they have another great ability," Mitoh said. "We are very interested in these small animals."

The study was published online Mar. 8 in the journal Current Biology.

Originally published on Live Science.

The series "Imaginary Earths" speculates what the world might be like if one key aspect of life changed, whether related to the planet or humanity.

Green skin is common in science fiction, from little green men to Hera Syndulla from "Star Wars Rebels" to Gamora from "Guardians of the Galaxy." But what if green skin were not just for fictional aliens? If humans had green skin, for instance, what if it granted us the ability to perform photosynthesis, which plants use to live off of sunlight?

Let's analyze what science says about similar abilities in other animals and ask award-winning science-fiction author John Scalzi how he thinks humans might hypothetically benefit from photosynthetic skin.

Related: 10 things we learned about humans

Plant-like animals

Every animal consumes food to survive. In contrast, plants rely on photosynthesis to create their own energy. However, some animals do use sunlight for a range of capabilities. 

For example, a number of animals benefit from solar-powered molecules. The pea aphid produces pigments that, with the aid of light, generate adenosine triphosphate, or ATP, the compound that powers reactions with cells. In addition, a stripe of yellow pigment on the exoskeleton of the Oriental hornet (Vespa orientalis) converts light to electricity, which could help to explain why these insects become more active during the middle of the day.

Other animals make use of actual photosynthesis, using sunlight, water and carbon dioxide to produce sugars and other vital compounds. Plants and algae rely on chloroplasts, structures within their cells, to carry out photosynthesis, but Elysia sea slugs can steal chloroplasts from algae they graze on, to help them live solely on photosynthesis for months. .

Many other animals reap benefits from photosynthesis by forming partnerships instead. For instance, most corals partner with photosynthetic symbiotic microbes known as zooxanthellae, while the eggs of spotted salamanders receive valuable oxygen from algae.

Engineering photosynthesis?

If other animals can reap benefits from photosynthesis, could humans? Even if photosynthesis could work in humans, it remains uncertain how much of an advantage we could actually gain from it. 

Plants can live off of photosynthesis because they grow broad, flat leaves to harvest as much light as possible. They also need less energy because they are far less active than animals.

According to Lindsay Turnbull, a plant ecologist at the University of Oxford in England, if the skin of a typical adult woman were photosynthetic like a leaf, the amount of surface area she had would satisfy only 1% of her daily energy requirements to survive. For a photosynthesizing woman to meet her energy demands, she would need a lot more skin — about a tennis court's worth, Turnbull estimated.

In addition, photosynthesis requires carbon dioxide. Plants have pores called stomata that they use to supply the gas to their cells. Assuming that photosynthetic humans possessed chloroplasts, they might need porous skin to let in carbon dioxide, but such pores might let other things leak in or out — for instance, moisture — in ways that might prove detrimental to the human body.

Solar-powered humans

Still, if humans had photosynthetic skin, even a tiny benefit might prove useful. In John Scalzi's Hugo Award-nominated novel "Old Man's War," soldiers are equipped with genetically engineered bodies that not only possess cybernetic brain implants and enhanced strength, speed, senses, endurance and dexterity, but also green, photosynthetic skin.

Although the soldiers of "Old Man's War" cannot get all of the energy they need to survive from their photosynthetic skin, in the novel, they are told it can "provide your body with an extra source of energy and to optimize your body's use of both oxygen and carbon dioxide. The result: You'll feel fresher, longer — and better able to perform your duties."

"I was thinking about how, if you were to take the human body into the chop shop, so to speak, to bling it out, what would you do to it?" Scalzi said. Photosynthetic skin "would be a supplementary passive modification, as opposed to an active modification — you could just sit there and accrue benefits from it in terms of keeping energized. It might be a 3% to 5% advantage in the scope of things, but that's a margin you didn't have before, and you're getting it for free."

How might photosynthesizing feel? "I suspect it would feel like being caffeinated all the time," Scalzi told Live Science. "You would wake up, and just like you would say, 'I need my coffee,' you'd want to get some light."

Assuming humans could successfully become photosynthetic, how might this change the course of history if, say, "someone went back in time and gave Cro-Magnons access to a CRISPR machine?" Scalzi said.

Scalzi said he doesn't think human society would change radically if people could photosynthesize, given the marginal benefits it would provide. Still, the most energy-dependent part of the body is the human brain. "So I suspect that any surplus energy that photosynthesis might give is going to be taken up by the brain, because it's a hungry, hungry, hungry organ," Scalzi said "That might potentially mean societies might hit certain marks of progress a little bit faster, maybe have reached the Industrial Revolution in 10,000 BCE instead of 1800 CE."

One might wonder if photosynthetic people might prefer moving to sunny climes. Although such people might receive a marginal boost from photosynthesis if they moved to a desert area, they would likely have other resource issues to deal with, such as a lack of water, Scalzi said. "There's always going to be trade-offs," he noted

And would photosynthetic humans prefer little or no clothing, to absorb all those rays? In some photosynthetic societies, clothing might become a symbol of the elite — a sign they get enough energy from food to not need photosynthesis. "You can imagine them saying, 'I'm rich, so I can cover up,'" Scalzi said.

So, would Scalzi want photosynthetic skin for himself? "On the grand list of body modifications I would want, it's kind of in the lower middle," he said. "It wouldn't hurt, but I don't see the benefit from it being so substantial that I would completely change the way I'd look to benefit from it.

"But if someone else is like, 'I'm going to be photosynthetic,' then you do you," Scalzi said. "I'm glad you're happy."

Originally published on Live Science.

In a forest in New Zealand, a vampire clings to life.

Once a mighty kauri tree — a species of conifer that can grow up to 165 feet (50 meters) tall — the low, leafless stump looks like it should be long dead. But, as a new study published today (July 25) in the journal iScience reminds us, looks are only surface-deep.

Below the soil, the study authors wrote, the stump is part of a forest "superorganism" — a network of intertwined roots sharing resources across a community that could include dozens or hundreds of trees. By grafting its roots onto its neighbors' roots, the kauri stump feeds at night on water and nutrients that other trees have collected during the day, staying alive thanks to their hard work.

"For the stump, the advantages are obvious — it would be dead without the grafts, because it doesn't have any green tissue of its own," study co-author Sebastian Leuzinger, an associate professor at the Auckland University of Technology in New Zealand, said in a statement. "But why would the green trees keep their grandpa tree alive on the forest floor while it doesn't seem to provide anything for its host trees?"

Leuzinger and his colleagues tried to answer that by studying nutrient flow through the vampire stump and its two closest neighbors. Using several sensors to measure the movement of water and sap (which contains important nutrients) through the three trees, the team saw a curious pattern: the stump and its neighbors seemed to be drinking up water at exact opposite times.

During the day, when the vibrant neighbor trees were busy transporting water up their roots and into their leaves, the stump sat dormant. At night, when the neighbors settled down, the stump circulated water through what was left of its body. The trees, it seemed, were taking turns — serving as separate pumps in a single hydraulic network.

So, why add a near-dead tree to your underground nutrient highway? While the stump no longer has any leaves, researchers wrote, it's possible that its roots still have value as a bridge to other vibrant, photosynthesizing trees elsewhere in the forest. It's also possible that the stump joined roots with its neighbors a long time ago, before it was, well, a stump. Since nutrients still flow through the stump's roots and into the rest of the network, the neighboring trees may never have noticed its loss of greenery.

However the trees became entwined, their mysterious teamwork is giving Leuzinger and his colleagues reason to rethink the very concept of what a forest is.

"Possibly we are not really dealing with trees as individuals, but with the forest as a superorganism," Leuzinger said.

These forest superorganisms may create added protection from droughts, the researchers speculated, giving trees with less access to water a chance to share resources with their better-hydrated neighbors. That's an especially valuable perk to have now, as the frequency and intensity of droughts are expected to increase around the world due to climate change.

Still, there may be drawbacks to the root grafting, as well. Just as nutrients can be shared swiftly between individuals, perhaps harmful pathogens could just as easily spread from a single infected tree to an entire forest via this underground root network. Kauri trees, in particular, are threatened by a disease called kauri dieback, which spreads through a soil-borne pathogen, the researchers wrote. Will community-mindedness be the downfall of the kauris, or will it be their salvation? Time, and further study of forest vampires, will tell.

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Originally published on Live Science.

Scientists have found electricity flowing in an unexpected place — across the surfaces of rocks. 

Mineral coatings on rocks turn sunlight into electricity, turning on like a light switch when the sun hits them, according to a study published April 22 in the journal Proceedings of the National Academy of Sciences.

Plants use photosynthesis to convert sunlight into chemical energy. And solar cells produce electricity through the photoelectric effect, in which sunlight jostles electrons free from atoms, causing current to flow in semiconductors like silicon. But scientists knew very little about natural, non-biological systems that produce electricity.

In the new study, researchers analyzed the the mineral coatings on rocks lying in northern China and coatings on karst — an eroded landscape of limestone — and red soil particles in southern China. [In Images: Mysterious Desert Varnish]

They used microscopes and X-ray spectroscopy— a method that reveals the elements that make up a substance— to figure out that the coatings were full of iron and manganese, two elements that are used in solar cell coatings.

They found that light transformed into electricity inside the coatings, but not in the underlying rock. When the light that hit the minerals changed, the photoelectric currents also shifted rapidly, turning on and off like a light switch, according to a statement. 

These natural photoelectric coatings cover vast expanses of desert, karst and red soil particles throughout the world, the authors noted. "The native semiconducting iron/manganese-rich coatings may play a role similar, in part, to photosynthetic systems and thus provide a distinctive driving force" for some of the principal chemical reactions on Earth’s surfaces,  the researchers wrote in the study.  

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• World's Most Famous Rocks
• Shine On: Photos of Dazzling Mineral Specimens

Originally published on Live Science.

If you listen closely, you can hear little plants harnessing the sun's energy. All you have to do is dive underwater and listen for the faint but distinctive "ping!" that red algae make while carrying out photosynthesis, a new study finds.

Just like plants on land, algae photosynthesize — essentially using the sun's rays to turn molecules of carbon dioxide and water into sugar and oxygen gas. Underwater, those teeny tiny oxygen bubbles rush upward. As these bubbles detach from the plant, they make a short "ping" sound, the researchers found.

"Many such bubbles create a large, distributed sound source over the seafloor," the researchers wrote in the study, published online Oct. 3 in the journal PLOS ONE. These noteworthy pings may help researchers monitor the health of coral reefs covered by these algae, they said. [In Photos: Diving in a Twilight Coral Reef]

The researchers first noticed the pings in Hawaii, when they discerned that healthy, protected reefs were making low-frequency sounds, while damaged reefs seemed to call out in higher-pitched sounds, Hakai Magazine reported.

"We were told the sound was from snapping shrimp, end of story," Simon Freeman, who works with his wife and study co-researcher Lauren Freeman as an oceanographer at the U.S. Naval Undersea Warfare Center in Rhode Island, told Hakai Magazine. "[But] there seemed to be a correlation between the sound and the proportion of algae covering the seafloor."

To learn more, the Freemans and their research team transferred 22 lbs. (10 kilograms) of invasive red algae (Gracilaria salicornia) collected from Hawaii's Kaneohe Bay into a tank filled with seawater. This helped them analyze any sounds the algae made, away from the clamor of the noisy ocean.

The experiment worked; the scientists recorded high-frequency pings, which sounded like the dings they heard from the distressed reefs.

Part of the corals' distress comes from algae that are smothering them, the researchers said. People are to blame for some of these algae spikes, largely because of overfishing of the fish that keep the algae in check, pollution from nutrient runoff and climate-change effects, they said.

Given that high agal cover is a strong indicator that coral reefs are struggling to survive, it's possible that monitoring the sounds of these agal bubbles could be a fast and noninvasive way for scientists to keep tabs on coral reef health, the researchers said.

"Right now, reefs are evaluated visually by divers," Simon Freeman told Hakai Magazine. But this method is expensive and time intensive, so "in the future, it might be possible to quickly listen to a coral reef soundscape, perhaps by using an autonomous vehicle, and evaluate how it may have changed from the previous year."

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Originally published on Live Science.

A lot of scientists think that major quantum effects like entanglement, in which particles separated by vast distances mysteriously link up their states, shouldn't work for living things. But a new paper argues that it already has — that scientists in 2016 have already created a sort of Schrödinger's cat — only with quantum-entangled bacteria.

Usually, we describe quantum physics as a set of rules that governs the behavior of extremely tiny things: light particles, atoms and other infinitesimally small objects. The larger world, at the bacterial scale (which is also our scale — the chaotic realm of life) isn't supposed to be anywhere near that weird.

That was what the physicist Erwin Schrödinger meant to say when he proposed his famous Schrödinger's cat thought experiment, as Jonathan O'Callaghan pointed out in Scientific American. In that thought experiment, a cat in a box would be exposed to a radioactive particle that had even odds of decaying or not. Until the box was opened, the poor cat would be both alive and dead at the same time, which seemed clearly absurd to Schrödinger. There's just something about the quantum world that doesn't seem to make sense in ours. [How Quantum Entanglement Works (Infographic)]

But scientists don't agree on where the boundary between the ordinary and the quantum world lies — or if it even exists at all. Chiara Marletto, a physicist at the University of Oxford and a co-author on the recent paper, which was published Oct. 10 in The Journal of Physics Communications, said that there's no reason to expect that there's a limit on the size of quantum effects.

"I'm interested in studying the border where quantum rules stop applying," she told Live Science. "Some people say that quantum theory is not a universal theory, so it does not apply to any object in the universe, but actually will at some point break down. My interest is to show that actually, that's not the case."

To that end, Marletto and her colleagues went back and looked at a paper published in 2017 in the journal Small that appeared to show some limited quantum effects in bacteria. They built a theoretical model of what might have really been going on in that University of Sheffield experiment, and it shows that those bacteria may have, in fact, become entangled with light particles.

Here's why that's such a radical idea:

Look at yourself, then look at the person next to you. You're physically separate beings, right?

But quantum mechanics tell us that this doesn't have to be the case. Particles, or collections of particles, can become bound up in one another, "entangled" so that their waveforms are entwined. Neither particle can be understood or described without also describing the other. And measuring a physical trait of one particle "collapses" the waveform of both particles. Separate the particles by thousands of miles, and you could still instantaneously learn the physical state of one of them by measuring only the other one.

According to current quantum theory, there's no limit to this effect. What works for a proton should work for an elephant. But in practice, bigger systems are far more difficult to entangle. And scientists have debated whether living things are simply too complex to entangle. You'd struggle to entangle two elephants for the same reason you'd struggle to teach those elephants to do pairs figure skating at an Olympic level: There's no specific law of nature saying that it's impossible, but most people would agree it's not possible.

And yet, in 2017, a team of researchers based at the University of Sheffield in England said they had created a state of what's known as quantum coupling in photosynthetic bacteria. They placed a few hundred bacteria in a tiny, mirrored room and bounced light around. (Based on the length of the mini room, only a certain wavelength of light persisted over time, known as the resonant frequency.) Over time, six of the bacteria appeared to develop a limited quantum connection to the light. So the resonant frequency of light inside the tiny room seemed to synchronize with the frequency at which electrons jumped in and out of position inside the bacteria's photosynthetic molecules. (For more on this effect, check out this link.)

Marletto said that her model shows that this effect likely involved more than just quantum coupling. There was likely something going on even weirder than what those experimentalists described, she said

The bacteria, she and her colleagues showed, likely became entangled with the light. What this means is that the equations used to define each of the waveforms — of both the light and the bacteria — become one equation. Neither is solvable without the other. (According to quantum mechanics, all objects can be described as both particle and wave, but practically speaking, in "large" objects like bacteria, the waveforms are impossible to see or measure.)

Like Schrödinger's proverbial cat in a box, the whole system seemed to exist in an uncertain netherworld: The light particles seem to have simultaneously both hit and missed the bacteria.

This doesn't prove the bacteria and the light were definitely entangled, however — there are other possible explanations that involve classical physics, and those haven't been ruled out yet, she said.

"What is missing in this experiment is the ability to confirm entanglement in a deeper way," she said.

Quantum experiments often involve measuring physical features of one entangled particle to figure out whether those features influence the other particle. In this case, that would have meant measuring physical traits of the bacteria in concert with physical traits of the light. That wasn't possible in this experiment, but Marletto said experiments are already being designed that could demonstrate true entanglement.

Even more interesting, she said, is the question of whether the bacteria use the entanglement in some way that's useful to them, though answering that question would take much more experimental work.

"It is possible that natural selection has led the bacteria to take advantage of quantum effects," she said.

Originally published on Live Science.

The forest is displeased. Trees are wobbling, the wind is howling, and huge tufts of Earth are rising and falling as if lifted by a humongous pair of lungs pumping just below the soil.

That's certainly what it looks like in a recent video making the rounds on social media. Filmed earlier this month in a forest in Sacre-Coeur, Quebec, Canada, the clip shows what appears to be the Earth itself doing a deep-breathing exercise, lurching up and down with unsettling force.

It's not an earthquake. It's not an Ent from "The Lord of the Rings." And it's not, thankfully, the snoring of some vengeful forest deity, marshalling her power before lashing out at whoever has been dumping cat poop into the nearby St. Lawrence River.

The real explanation is much less whimsical, and much less terrifying. Simply put, it's the wind.

"During a rain- and wind-storm event, the ground becomes saturated, 'loosening' the soil's cohesion with the roots as the wind is blowing on a tree's crown," Mark Vanderwouw, and arborist working with Shady Lane Expert Tree Care in Ontario, Canada, told The Weather Network. "The wind is trying to 'push' the trees over, and as the force is transferred to the roots, the ground begins to 'heave.'"

OK, maybe that is sort of epic and terrifying. It's a clash between the elements: wind versus root, air versus Earth. The terrestrial forces seem to have won this skirmish. However, Vanderwouwadded, if the wind blew a little harder or lasted a little longer, the tree roots would likely start snapping, and the forest would start to topple.

That's pretty dramatic. But if you're still disappointed that this excellent video does not, in fact, show a forest "breathing," remember that trees actually do breathe, by replacing atmospheric carbon dioxide (CO2) with oxygen via photosynthesis. The soil breathes, too, in a backward sort of way. Tiny microbes living underground chow down on the CO2 stored in plant roots and dead leaves, then release that CO2 back into the air. This is called soil respiration, and it's been happening a lot more in the last 25 years, thanks to climate change.

So, there you have it: Forests can breathe — but not in obvious, visible ways — and climate change is causing them to hyperventilate. Probably not what you hoped to learn by clicking on this article, but that's life. Take a deep, cleansing breath and try to make peace with that.

Originally published on Live Science.

You know it's hot out there when even the soil is hyperventilating.

According to a new study published yesterday (Aug. 1) in the journal Nature, there's about twice as much carbon dioxide (CO2) stored in Earth's soil as there is floating around the atmosphere, and for the last few decades, that underground greenhouse gas has been leaking out at a significantly increased rate.

Based on more than 2,000 sources of climate data taken from ecosystems around the world, a team of soil scientists found that the rate of CO2 released from Earth's soil has increased globally by about 1.2 percent in just 25 years — and you can blame that on hot, hungry microbes.

"We're talking about a huge quantity of carbon," study co-author Vanessa Bailey, a soil scientist at Pacific Northwest National Laboratory in Washington state, said in a statement. "Microbes exert an outsize influence on the world that is very hard to measure on such a large scale."

The breathing Earth

Dirt doesn't actually breathe, of course, but it sort of looks that way when tiny, underground organisms help release the CO2 stored in plant roots, dead leaves and other natural detritus. Hungry microbes gorge on the tasty carbon stored in this plant matter, and then release carbon dioxide as a natural byproduct of this feeding, just as you do when you exhale after a deep breath.

This process is known as "soil respiration," and it's an important complement to photosynthesis — the process by which plants turn CO2, water and light into energy — helping to keep ecosystems around the world running smoothly.

But lately, researchers have found that as global temperatures rise, microbes in the soil have been releasing CO2 faster than plants can snatch it up again. Previous studies have indicated that tree roots and certain microbes both respire more frequently at higher temperatures (up until a certain point, when the intense heat causes the organisms to stop functioning completely). But the exact effects of that increase in respiration had never been studied on a global scale until now.

To better understand the potential links between rising global temperatures and soil respiration, a team of researchers led by Ben Bond-Lamberty at the Joint Global Change Research Institute at the University of Maryland, College Park, examined data from two huge global nature surveys: the Global Soil Respiration Database and FLUXNET, which collectively draw soil, temperature, rainfall and other data from a network of more than 2,000 sources across several ecosystems.

The data showed that the rate of global soil respiration had increased by about 1.2 percent in the 25-year window between 1990 and 2014. Most of that growth was due to increased microbial action; the tiny creatures in Earth's soil are freeing more and more greenhouse gases from our planet's surface.

The panting Earth

While a 1.2 percent increase might not seem significant on its face, the researchers made it clear that even a modest change like this represents a "massive" ecosystem shift over a relatively short time. And while the full effects of this microbial huffing and puffing are hard to estimate, it's possible that all that extra CO2 will feed a self-intensifying loop of atmospheric warming and soil respiration over the years to come.

"Depending on how other components of the carbon cycle might respond due to climate warming, these soil changes can potentially contribute to even higher temperatures due to a feedback loop," Bond-Lamberty said in the statement. "Soils around the globe are responding to a warming climate, which in turn can convert more carbon into carbon dioxide which enters the atmosphere."

The study has several limitations, the authors noted. The data examined came mainly from studies of the Northern Hemisphere and included only spotty surveys of high Arctic latitudes and the tropics, so does not represent a complete picture of the planet's soil. It's also very hard to tease out cause and effect in any observational study like this one, the authors wrote, so further analysis of ecosystems around the world is required.

Originally published on Live Science.

Is bright pink the new black? Well, not exactly, but it is the world's oldest-known color produced by a living organism, according to new research.

Researchers extracted the pigment from bacteria fossils preserved in rocks under the Sahara Desert in Mauritania, West Africa. Inside those teensy bacteria, the scientists found chlorophyll — a pigment used today by plants for photosynthesis — dating back to about 1.1 billion years ago. That's about 600 million years older than similar chlorophyll fossils found previously, scientists reported in the new study. [In Images: The Oldest Fossils on Earth]

Their findings hint that cyanobacteria, bacteria that survive on sunlight, appeared much earlier than algae, which have been traced to around 650 million years ago. And bacteria likely dominated Earth's ancient oceans for hundreds of millions of years, according to the study.

Chlorophyll is what gives modern plants their green color, though the fossilized chlorophyll in the cyanobacteria samples was dark red and deep purple in its concentrated form, the scientists reported.

When they pulverized the fossils to analyze the bacteria molecules, the researchers distilled the colors to find a brilliant pink. This colorful remnant suggests that ancient sunlight-eating organisms cast a pink tint to a long-gone ocean, lead study author Nur Gueneli, of the Research School of Earth Sciences at the Australian National University (ANU), said in a statement.

Chlorophyll this ancient is preserved only under exceptional circumstances, study co-author Jochen Brocks, an associate professor with ANU's Research School of Earth Sciences, told Live Science in an email. First, dead organic matter — a bloom of cyanobacteria, for example — sinks quickly onto the seafloor. Once there, it must be isolated from any exposure to oxygen, which spurs decay, and then the rock that holds the material has to remain in one piece for a billion years, Brocks said.

Her reaction to seeing colors produced by organisms that lived more than a billion years ago? "Sheer amazement," Brocks said. Even algae, one of the most ancient forms of life, was absent or scarce at the time of these chlorophyll-swallowing bacteria, the researchers wrote in the study.

It was a few hundred million years until algae would begin to multiply, ultimately forming the base of a food web that would eventually fuel the evolution of larger animals, Brocks told Live Science.

But until the rise of algae, and more-complex organisms, the planet belonged to the bacteria.

"This was truly an alien world," Brocks said.

The findings were published online July 9 in the journal Proceedings of the National Academy of Sciences.

Original article on Live Science.

Algae can be glamorous, too: In the crisp, clear waters off the Atlantic coast in the United Kingdom, an unassuming, bushy seaweed glows in deep blues and greens. It turns out that this species is packed with opals — but, not the gemstone.

Rainbow wrack (Cystoseira tamariscifolia) is a type of brown alga found in the Mediterranean Sea and off the Atlantic coast of Europe. In the water, these algae glow. And although there are many glimmering organisms that live in the water — for example, bioluminescent jellyfish and lantern fish — most produce their own light.

Rainbow wrack, on the other hand, doesn't. Instead, just like the precious gemstone, it uses a crystal structure to reflect sunlight, according to a new study published April 11 in the journal Science Advances.

To study the shimmering seaweed, a group of researchers gathered the plant from a typical tourist-inhabited beach in southwest England during low tide. Using a variety of microscopy techniques, they discovered that the alga's cells contained baggies of "opals." [Gallery: Eye-Catching Bioluminescent Wonders]

Again, not the gemstone. Physicists use the term "opal" to describe any material with a very specific, tightly packed lattice structure, said senior study author Ruth Oulton, a physicist at the University of Bristol. Whereas gemstone opals are made from spheres of silicon dioxide, this algal opal is made from oil droplets called lipids. But all "opals" reflect light in very similar ways. (Opals are also found in insects: shiny beetles and some butterflies have hard opal structures on their exteriors.)

It's very rare for plants to have opal-like structures, but if they do, they're usually found in a hard exterior, like cellulose in cell walls, Oulton told Live Science. In the case of rainbow wrack, "it's the first time that an opal's been found that's not made of hard material inside a living thing."

What's more, the researchers found that rainbow wrack reacted to the light, changing its structure to dim and brighten itself, depending on the conditions. When there was ample light, the alga took apart its tightly packed opal structure to dim its glow. But when surrounded by near darkness, within a few hours it re-ordered all of the spheres back together into a lattice. Soon, it was glowing again.

The researchers don't know exactly why rainbow wrack adopted this mechanism. But because this species lives in an area where changes in the tides sometimes leave it exposed on the beach and other times buried under 9 feet (3 meters) of water, they think it could have evolved to regulate the amount of light that reaches its chloroplasts — organelles that direct photosynthesis in cells. It's more than likely not a coincidence that the baggies of opals are surrounded by chloroplasts, Oulton said.

"What we know is seaweed itself can change [its] opal … when it gets lighter, the opal structure disappears," Oulton said. "When [a] beetle dies, the opal is still there, but if the seaweed were to die, all of it would disappear," she added.

Scientists can't yet replicate the process of turning the opals on and off in the lab, but they'd like to be able to. After talking to some chemists, the team figured out that this new finding could open up new possibilities, such as biodegradable displays. For example, if they can mimic rainbow wrack's process of packing and unpacking opal structures based on light, researchers may be able to create biodegradable packaging and labels from something as commonplace as coconut oil.

This could take the form of labels on food packaging that turn a different color, based on expiration dates; or plastic in packaging that totally disintegrates after a while, the researchers said.

In the meantime, rainbow wrack will continue to sway in high tides, looking glamorous as always.

Originally published on Live Science.

Ancient rocks from a remote Canada island contain the oldest algae ever discovered.

The samples, found on Canada's Baffin Island, also reveal roughly when plants had the components necessary for photosynthesis, a new study finds.

The finding reveals that Bangiomorpha pubescens, the oldest known algae on Earth, is more than 1 billion years old. Working backward, the researchers figured out that algae could likely harvest the sun's energy through photosynthesis about 1.25 billion years ago. [Photo Timeline: How the Earth Formed]

"I think it's pretty spectacular that this fossil is almost identical to red algae [one of the oldest groups of algae that still exists today], and we have shown that it is over 1 billion years old," said study lead researcher Timothy Gibson, a doctoral student in the Department of Earth and Planetary Sciences at McGill University, in Canada.

Earth's air

When a plant photosynthesizes, it uses sunlight to fuel a reaction between water and carbon dioxide, producing carbohydrates and oxygen. Bacteria have been photosynthesizing since at least 2.5 billion years ago, but B. pubescens is the first known example of a eukaryote that could photosynthesize. (Eukaryotes are organisms, such as plants, some algae and animals, whose cells have a membrane surrounding the nucleus and other organelles that are inside them.)

"Prior to about 2.5 billion years ago, there was essentially no oxygen in the ocean," Gibson said.

Primeval bacteria helped change that. "This early photosynthesis is responsible for the very earliest atmospheric oxygen," Gibson said.

However, there was more uncertainty when it came to more complex organisms' ability to photosynthesize.

Narrowing range

Researchers originally published dates for B. pubescens in 1990 in the journal Science, stating that the algae — which sported the first widely accepted evidence for photosynthesis in plants (which includes algae) — was between 1.2 billion and 720 million years old.

But this time window was vast, so in the current study, Gibson and colleagues narrowed it by collecting and dating new samples of the black shale found in rock layers around the algae fossils. Their new analysis showed that B. pubescens lived between 1.06 billion and 1.03 billion years ago, with its most likely age being 1.047 billion years old, Gibson said.

After the researchers determined the age of B. pubescens, they used a molecular clock analysis — that is, a computer model that uses rates of genetic change to calculate evolutionary events — to figure out when photosynthesis likely began in eukaryotes.

The analysis suggests that "1.25 billion years ago, a complex but microscopic organism 'swallowed' a simple photosynthetic bacterium and gained its photosynthetic powers," Gibson told Live Science in an email. "It was then able to pass the DNA that codes for photosynthesis down to its offspring, and now, essentially all modern plants use the same organelle — the chloroplast — for photosynthesis."

However, although B. pubescens has helped establish when eukaryotes began to photosynthesize, it's still unclear when Earth's oxygen levels rocketed to modern levels, Gibson said.

"The question of when oxygen reached anything like modern levels is a topic we are still trying to pin down, but it likely wasn't until closer to half a billion years ago," Gibson said.

The study was published online Dec. 8 in the journal Geology.

Original article on Live Science.

The 2 minutes of darkness caused by the total solar eclipse earlier this week may seem momentous, but it's nothing compared with the prolonged darkness that followed the dinosaur-killing asteroid that collided with Earth about 65.5 million years ago, a new study finds.

When the 6-mile-wide (10 kilometers) asteroid struck, Earth plunged into a darkness that lasted nearly two years, the researchers said.

This darkness was caused, in part, by tremendous amounts of soot that came from wildfires worldwide. Without sunlight, Earth's plants couldn't photosynthesize, and the planet drastically cooled. These two key factors likely toppled global food chains and contributed to the mass extinction at the end of the dinosaur age, known as the Mesozoic, according to the study. [Wipe Out: History's Most Mysterious Extinctions]

The finding may help scientists understand why more than 75 percent of all species, including the non-avian dinosaurs, such as Tyrannosaurus rex, and large marine reptiles, such as the plesiosaur, went extinct after the asteroid slammed into what is now Mexico's Yucatán Peninsula, the researchers said. 

Killer asteroid

When the space rock smashed into Earth, it probably triggered earthquakes, tsunamis and even volcanic eruptions, the researchers said. The asteroid hit with such force that it launched vaporized rock sky-high into the atmosphere. Up there, the vaporized rock would have condensed into small particles, called spherules.

When the spherules plunged back down to Earth, they collided with air molecules, causing friction and heating to temperatures hot enough to ignite fires around the world. In fact, a thin band of spherules can still be found in the geologic record, the researchers said.

Most large Mesozoic land animals died in the asteroid's immediate aftermath, "but animals that lived in the oceans or those that could burrow underground or slip underwater temporarily could have survived," the study's lead researcher, Charles Bardeen, a project scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, said in a statement.

"Our study picks up the story after the initial effects — after the earthquakes and the tsunamis and the broiling," Bardeen said. "We wanted to look at the long-term consequences of the amount of soot we think was created and what those consequences might have meant for the animals that were left."

Earth without photosynthesis

Even though researchers found evidence for the asteroid in the late 1970s, there still isn't "universal agreement" on how long Earth was shrouded in darkness after the space rock smacked into the planet, Bardeen told Live Science. [Doomsday: 9 Real Ways Earth Could End]

Bardeen and his colleagues used the most up-to-date estimates of the amount of fine soot in the geologic record — that is, 15,000 million tons. Then, they plugged that amount into the NCAR-based Community Earth System Model (CESM) — a modern chemistry-climate model that factors in components related to the atmosphere, land, ocean and sea ice. This model allowed the scientists to simulate the effect of soot in the years following the asteroid impact.

"Different studies have assumed various types of particles including dust, sulfates and soot," Bardeen told Live Science in an email. "All of these particles can block enough sunlight to cool the surface, but only soot is so strongly absorbing that it is self-lofting, can heat the stratosphere and reduces sunlight at the surface light to very low levels."

The new results show what a catastrophic effect the soot had on Earth.

"Our study shows it is dark enough to shut down photosynthesis for up to two years," Bardeen said. "This would have a devastating effect, particularly in the ocean, since the ocean relies upon phytoplankton as a primary source of food and loss of this would be catastrophic to the entire food chain."

Even if the soot levels had been one-third this estimated amount, photosynthesis would have still been blocked for an entire year, the researchers found.

Other catastrophic effects

In addition to stopping photosynthesis, this worldwide cloud of soot would have prevented much of the sun's heat from reaching Earth. After three years following the crash, the land and oceans would have cooled by as much as 50 degrees Fahrenheit (28 degrees Celsius) and 20 degrees F (11 degrees C), respectively, the researchers found. [Crash! 10 Biggest Impact Craters on Earth]

In contrast, the upper atmosphere, known as the stratosphere, would have warmed because that's where the soot floated around, absorbing the sun's heat. These roasting temperatures would have depleted the ozone, and also allowed for vast quantities of water vapor to hover in the stratosphere. When this water vapor chemically reacted in the stratosphere, it would have created hydrogen compounds that led to further ozone destruction, according to the researchers.

As the ozone disappeared and the soot cleared, damaging doses of ultraviolet light reached Earth, harming life there, the researchers said.

When the stratosphere eventually cooled down, the water vapor there condensed and began raining, abruptly washing away the soot, Bardeen said. As some soot left, the air there cooled, which in turn led the water vapor to condense into ice particles, which washed away more soot.

Once this cooling cycle repeated enough times, the thinning soot layer vanished within months, the researchers found.

Bardeen credited his friend Betty Pierazzo, a senior scientist at the Planetary Science Institute, a nonprofit headquartered in Tucson, Arizona, with securing funding from NASA for an earlier study that enabled and inspired this study. Unfortunately, Pierazzo died before research on the end-Cretaceous asteroid got underway.

Bardeen also noted several limitations, including that the model is based on a modern Earth, and that at the end of the Cretaceous period Earth's continents were in different locations and the planet also had different atmospheric properties, such as different concentrations of gases.

The study was published online Monday (Aug. 21) in the journal Proceedings of the National Academy of Sciences.

Original article on Live Science.

Humans can be vegetarians, choosing to forgo meat, but what about trees? After all, trees need only soil, sunlight and water to survive, right?

"The short answer is no," said Nicholas Money, a professor of botany at Miami University in Ohio. "Plants are not vegetarian. But the devil, as always, is in the details."

Those details depend on how strictly vegetarianism is defined. Trees don't directly "eat" animals, but they do consume them with the help of fungi, Money said. [How Tall Can Trees Grow?]

It's well known that trees can make simple sugars through photosynthesis— that is, basically using sunlight to fuel a reaction between water and carbon dioxide, resulting in carbohydrates and oxygen.

However, trees also need minerals such as potassium, calcium, sodium and certain metals, Money said. In order to get these nutrients, they need fungi's help.

Fungi are literally everywhere in forests' soil, according to Money, as reported during a 2016 Radiolab episode that explored the relationship between trees and fungi. This massive fungal network is composed of millions of microscopic filaments that run every which way. The network constantly soaks up water from the soil and always looks for a new meal.

"The mushroom itself is just the most conspicuous part of this huge [fungal] organism that's pulsing away underground in the soil," Money told Live Science.

The fungal network produces enzymes called proteases that can break down fats and proteins from dead organisms, such as tiny worms known as nematodes, that live in the soil. However, because fungi can't photosynthesize, they can't make their own sugars.

This need for sugar drives the fungi's relationship with trees, Money said. The fungi's filaments connect to the tree's roots — basically, covering the roots like a well-fitted glove — and send out structures that penetrate the roots, enabling a two-way nutrient exchange.

Once the exchange is established, the tree can give the fungi some of its sugar, and in return, the fungi give the tree minerals dissolved in water.

It's a perfect symbiotic relationship: "One partner is not gaining more in the relationship," Money said. "It's mutually beneficial."

In fact, the relationship has its own name: mycorrhiza, which is Greek for "fungus root," Money said.

Thus, trees consume animal components through this mycorrhizal relationship, he said.

"In this sense, depending on your definition of vegetarianism, perhaps we can't recognize trees as completely vegetarians, since some of the nutrients they absorb come from animal carcasses," Money said.

Original article on Live Science.

More than 200 feet (60 meters) below the ocean's surface, where the water is cold and only about 1 percent of the daylight above penetrates, is a dim, blue world filled with little-understood creatures. Now, researchers have discovered that the corals that inhabit this "twilight zone" have a never-before-seen adaptation that enables them to eke out enough light energy to survive.

The photosynthetic algae that live on and power these corals have unusual cellular "machinery" that enables them to conduct photosynthesis more efficiently than species that live at shallower depths, the researchers reported Oct. 17 in the journal Frontiers in Marine Science.

"It's unlike anything we've seen on land, or anything we've even seen in the shallow reefs," said David Gruber, a marine biologist at the City University of New York and one of the researchers on the study. [See Photos of the Deep 'Twilight' Coral Reefs]

Capturing a limited resource

On land and in the water, plants use cellular structures called light-harvesting complexes, or photosynthetic antennas, to capture photons (particles of light) and transfer them to the photosynthetic complexes that convert light into usable energy. The photosynthetic antennas are made of various proteins and chlorophyll pigments. In dim forests on land, plants in the underbrush often evolve very large antenna complexes to wring every drop of light out of the sky, Gruber said.

But that's not what the researchers found 213 feet (65 m) down in the northern Red Sea when they collected coral called Stylophora pistillata from reefs there. Inside the coral is symbiotic algae called Symbiodinium, which provide the coral oxygen and energy from photosynthesis in exchange for nutrients and protection. This makes for relatively easy living in shallow reefs, where sunlight is abundant. But below about 130 feet (40 m), the ocean gets dim. This is the "mesophotic" zone, where it's always twilight. At about 330 feet (100 m), only 1 percent of the sunlight above can reach down below. And only blue wavelengths of light can penetrate.

It might make sense for algae living in the mesophotic zone to build huge photosynthetic antennas. But that's not what Symbiodinium does. In fact, when Gruber and colleagues from the Hebrew University of Jerusalem and the University of Haifa, both in Israel, analyzed the deep-living algae, they found that the algae antenna structures were actually smaller than that of shallower Symbiodinium algae.

Extreme environment

Instead of building bigger antennas, the algae modified its light-gathering system. Plants like algae have two types of cellular machines for converting light into sugars: photosystem I and photosystem II. Symbiodinium relies more heavily on photosystem II but positions the cellular machinery close to the machinery of photosystem I. This makes it easier for the two systems to share energy. They also adjust the types of light-snatching proteins in their cellular membranes, the researchers said. [Images: Colorful Corals of the Deep Barrier Reef]

Diving to these coral habitats is hard for humans; commercial scuba divers don't usually go below about 130 feet. To get to the twilight zone of the Red Sea, the researchers, led by lead diver Shai Einbinder, donned tri-gas rebreather systems, which enable divers to go lower while facing a smaller risk of serious problems such as nitrogen narcosis (an altered state of consciousness that occurs when nitrogen enters the bloodstream at the increased pressures seen at extreme water depths). Still, divers stay down only a few minutes because they must ascend very slowly to equilibrate to the lower pressures at the surface and thus avoid decompression sickness, also known as "the bends", Gruber said.

Over the course of four years of diving, the scientists took some samples of deep-reef coral and transferred them to shallow environments, and took shallow corals and transferred them to deeper areas. They did this slowly, moving the corals only 16 feet (5 m) every two weeks. They found that the corals collected in water depths of about 10 feet could hang on to life at 213 feet. Corals from the deep, however, couldn't survive at shallow depths. They lacked the natural compounds that protect corals from the sun's damaging ultraviolet light.

"They didn't have the 'sunscreen,'" Gruber said. "The light was just burning them out."

The researchers studied only one species of algae, and there are probably many more adaptations among the photosynthesizers of mesophilic reefs, Gruber said.

"I'm never unimpressed by the way nature evolved unique traits to allow life in some of the most seemingly unhospitable places," he said.

Original article on Live Science.

The excess carbon dioxide in the atmosphere has created a greener planet, a new NASA study shows.

Around the world, areas that were once icebound, barren or sandy are now covered in green foliage. All told, carbon emissions have fueled greening in an area about twice the size of the continental United States between 1982 and 2009, according to the study.

While lush forests and verdant fields may sound like a good thing, the landscape transformation could have long-term, unforeseen consequences, the researchers say. 

The radical greening "has the ability to fundamentally change the cycling of water and carbon in the climate system," lead author Zaichun Zhu, a researcher from Peking University in Beijing, said in a statement. [Video: See Global Warming Make Earth Greener]

Fuel for plants

Green leafy flora make up 32 percent of Earth's surface area. All of those plants use carbon dioxide and sunlight to make sugars to grow — a process called photosynthesis. Past studies have shown that carbon dioxide increases plant growth by increasing the rate of photosynthesis.

Other research has shown that plants are one of the main absorbers of atmospheric carbon dioxide. Human activities, such as driving cars and burning coal for energy, account for about 10 billion tons of carbon dioxide emissions per year, and half of this CO2 is stored in plants.

"While our study did not address the connection between greening and carbon storage in plants, other studies have reported an increasing carbon sink on land since the 1980s, which is entirely consistent with the idea of a greening Earth," said study co-author Shilong Piao, of the College of Urban and Environmental Sciences at Peking University.

However, it wasn't clear whether the greening seen in satellite data over recent years could be explained by the sky-high CO2 concentrations in the atmosphere (the highest the planet has seen in 500,000 years).  After all, rainfall, sunlight, nitrogen in the soil and land-use changes also affect how well plants grow.  

To isolate the causes of planetary greening, researchers from around the world analyzed satellite data collected by NASA's Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration's Advanced Very High Resolution Radiometer instruments. They then created mathematical models and computer simulations to isolate how each of these variables would be predicted to influence greening. By comparing the models and the satellite data, the team concluded that about 70 percent of the greening could be attributed to atmospheric carbon dioxide concentrations, the researchers reported Monday (April 25) in the journal Nature Climate Change. 

"The second most important driver is nitrogen, at 9 percent. So we see what an outsized role CO2 plays in this process," said study co-author Ranga Myneni, an earth and environmental scientist at Boston University.

Warming still worrisome

While green shoots may be good, excess CO2 emissions also bring a host of more worrisome consequences, such as global warming, melting glaciers, rising sea levels and more dangerous weather, according to accumulating research.

What's more, the greening may be a temporary change. 

"Studies have shown that plants acclimatize, or adjust, to rising carbon dioxide concentration and the fertilization effect diminishes over time," said Philippe Ciais, associate director of the Laboratory of Climate and Environmental Sciences in Gif-sur-Yvette, France.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Slimy microbes called cyanobacteria use their teensy bodies as lenses to collect light and "see," before growing little legs to inch toward those rays, new research suggests.

That means the basic workings of these miniature light collectors may not be so different from those of cameras or the human eye, the researchers say.

"The idea that bacteria can see their world in basically the same way that we do is pretty exciting," study lead author Conrad Mullineaux, a microbiologist at the Queen Mary University of London, said in a statement. "Our observation that bacteria are optical objects is pretty obvious with hindsight, but we never thought of it until we saw it. And no one else noticed it before either, despite the fact that scientists have been looking at bacteria under microscopes for the last 340 years." [Watch Cyanobacteria 'See' With Their Tiny Eyeball Bodies]

Primitive light harvesters

Cyanobacteria, or blue-green algae, are some of the most ancient life-forms on the planet. The single-celled bacteria first winked into existence about 2.7 billion years ago, and were among the earliest organisms to use photosynthesis, harnessing the sun's energy to produce oxygen from carbon dioxide and water.

But in order to gather energy from the sun, cyanobacteria must have a way to sense light, researchers reasoned. Past studies showed that bacteria have simple light receptors, and that they do move toward light — a process known as phototaxis.

Move toward the light

But it wasn't exactly clear how these bacteria were sensing the light. To get a better picture, Mullineaux and his colleagues looked at the Synechocystis genus of cyanobacteria — a green, spherical bacteria just 0.003 millimeters in diameter (about the width of a single strand of spider silk), which often forms a slimy film in freshwater lakes.

The team placed the pond scum on microscope slides and watched the microbes swim with different lighting conditions. In one setup, they used a light diffuser to create a gradient of more intense light from one side of the slide to the other; the diffuser scattered light rays so that they came from every which way.

In a second setup, the light came from one side of the slide, and in the third setup, the researchers used two different light sources placed on two adjacent sides of the slide.

When the researchers placed the bacteria in the light gradient, the bacterial movement was random. However, when the bacteria were exposed to light from one side, they migrated toward that light. In the setup with two light sources, at both ends of the slide, the bacteria moved to a spot in between the two. In essence, the slimy, single-celled creatures were somehow sensing the direction the light was coming from.

The team also found that soon after being illuminated, the blue-green algae grew little tentacles called pili, which they attached to a surface and then retracted to inch toward the light source.

"These images reveal that each cell acts as a microscopic spherical lens, focusing an intense light spot close to the opposite side of the cell from the light source and the direction of movement," the researchers wrote in the Feb. 9 issue of the journal eLife. This pinging of light then spurred the bacteria to move toward the light.

Tiny eyes

To prove that the bacteria were acting as tiny eyes, the team spliced a gene into the bacteria that produced a fluorescent dye throughout a cell layer, called the periplasm, that encircled the bacteria and sits just inside the outer cell membrane. When the team hit the cyanobacteria with light, spots on the periplasm opposite to the light source glowed green, proving that light hitting the front of a cell was bent, or refracted, and sent to the opposite side.

This process isn't too different from what goes on in the human eyeball, where light shines through the cornea and is then focused toward the back of the eye, onto the retina. A cyanobacterium, however, is 500 million times smaller than the human eye, and the algae likely view only the blurry outlines of objects that the human eye could see clearly, the researchers said.

"The physical principles for the sensing of light by bacteria and the far more complex vision in animals are similar, but the biological structures are different," co-author Annegret Wilde, a researcher at the University of Freiburg in Germany, said in the statement.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Underwater volcanic eruptions may have delayed oxygen from building up in the atmosphere of primeval Earth for hundreds of millions of years, researchers say.

The finding sheds light on how Earth became the oxygenated world it is today, scientists added.

"Our research shows how the high concentrations of iron in the Earth's past could have limited photosynthesis," said lead study author Elizabeth Swanner, a geomicrobiologist at the University of Tübingen in Germany. Photosynthesis is the process by which plants and other organisms turn sunlight into sugar, and it produces oxygen as a byproduct.

Although life-sustaining oxygen gas currently makes up about a fifth of the Earth's air, very early in the planet's history, oxygen was rare in the atmosphere. The first time the element suffused Earth's primordial atmosphere to any great extent was about 2.3 billion years ago in what is called the Great Oxidation Event. Prior research suggests this jump in oxygen levels was almost certainly due to cyanobacteria — microbes that, like plants, photosynthesize and produce oxygen.

However, recent research examining ancient rock deposits suggested that oxygen may have transiently existed in the atmosphere up to 3 billion years ago, hundreds of millions of years before the Great Oxidation Event. This would mean that sunlight-dependent life evolved very early in Earth's history, sometime during the Archean Era, about 2.5 billion to 4 billion years ago.

But if photosynthetic life arose that early on Earth, then it is a mystery why oxygen didn't suffuse the planet's atmosphere until much later. Past studies suggested potential explanations, including that early photosynthesis may have been an inefficient process, that oxygen would have been poisonous to the microbes that first produced the element, and that there was a dearth of key nutrients that photosynthetic life would have needed to grow. [World's 10 Weirdest Geological Formations]

Iron is one nutrient that is key to photosynthetic life in modern oceans. And underwater volcanic activity, which was common in the late Archean Era before the Great Oxidation Event, would have delivered large amounts of a soluble form of iron, known as "reduced iron," to the oceans, Swanner and her colleagues noted.

To learn more about the early history of oxygen on Earth, scientists investigated the effects of reduced iron on a common type of modern cyanobacteria known as Synechococcus. Nowadays, photosynthetic ocean microbes generate about 12 percent of Earth's oxygen.

In lab experiments, the researchers found that the reaction of reduced iron with oxygen from the cyanobacteria is actually toxic to this cyanobacterium, decreasing both growth rates and oxygen production. That's because the reaction increases levels of molecules called reactive oxygen species, which damage cells.

The researchers noted that ancient periods of underwater volcanism, which would have released reduced iron into seawater, generally coincided with signs of reduced oxygen levels in Archean sediments. Underwater, iron-laden volcanic plumes might have temporarily limited oxygen production by poisoning oxygen-producing microbes, the scientists suggested.

It remains uncertain whether iron had the same effect on ancient cyanobacteria as it does on their modern counterparts. However, Swanner said she thinks it's likely that the earliest cyanobacteria did not have enzymes to detoxify reactive oxygen species, making them even more vulnerable to these molecules than are modern cyanobacteria. "I think using modern cyanobacteria in the lab is a fairly conservative approach," Swanner told Live Science.

Future research can explore how volcanic iron might have delayed the evolution of oxygen-dependent life forms, Swanner said.

The scientists detailed their findings online today (Jan. 5) in the journal Nature Geoscience.

Follow Live Science @livescience, Facebook & Google+. Originally published on Live Science.

Brilliant shades of blue and aqua coat the iridescent lips of giant clams, but these shiny cells aren't just for show, new research finds. The iridescent sheen directs beams of sunlight into the interior of the clam, providing light for algae housed inside.

In a symbiotic return, the algae use that sunlight to power photosynthesis, resulting in energy for the giant clam. "It ends up being a large part of the energy budget of the clams," said study researcher Alison Sweeney, an assistant professor of physics and astronomy at the University of Pennsylvania.

Essentially, the oversize mollusks, which can measure more than 4 feet (1.2 meters) long, have a natural solar energy system hiding in their shells.

Most iridescent cells — including those that impart a vivid blue to the morpho butterfly, the glittery colors of beetles and the shine of birds' feathers — are dead, much like fingernails and human hair. But the iridescent cells of squid and giant clams are alive. [Marine Marvels: Spectacular Photos of Sea Creatures]

So, the researchers wondered, "What on Earth is a giant clam doing with a living iridescent cell?" Sweeney said.

Giant clams have a dull outer shell, as well as a weighted shell hinge that helps them point their lips up toward the sunlight. Perhaps the iridescent cells, called iridocytes, play an optical function, the researchers reasoned.

The team traveled to Palau, an island east of the Philippines in the tropical Pacific Ocean, to gather information about the giant clams. "We put this into a computer model about how we think light propagates through the clams," Sweeney said. "[But] nobody actually believed it," she added, referring to how the light was reflected back into the shells of the clams.

So, they returned to Palau to take detailed measurements of light inside the clams — Tridacna derasa, T. maxima and T. crocea — with the help of a fiber-optic probe. The iridescent cells reflected a remarkable amount of light into the clam, more than the scientists had initially expected, Sweeney said. Clam tissue with iridocytes has about fivefold more particles of light, called photons, deep inside the tissue than clam tissue without iridocytes does, they found.

"We're very excited by our surprising discovery," said study researcher Dan Morse, a professor of biomolecular science and engineering, and director of the Marine Biotechnology Center at the University of California, Santa Barbara.

"The brilliantly reflective cells of the giant clam actually redirect photons from sunlight deeper into the clam's tissue, gently and uniformly illuminating millions of symbiotic algae that live there, so they can provide nutrients to their animal host by photosynthesis," Morse wrote in an email to Live Science.

The algae's configuration is also efficient, the researchers found. If the algae were spread horizontally across the clam's tissue, only the top layers of algae would get light. The giant clam, however, doesn't have this obstacle. Instead, the algae are piled into vertical columns that allow the reflective cells to shine light along the sides of the columns — not just the algae on top.

The reflected light is also less intense than direct sunlight, so the algae don't get fried, Sweeney said.

The study is "very interesting," Euichi Hirose, a professor of invertebrate biology at the University of the Ryukyus in Japan, told Live Science in an email.

"Now, we know the giant-clam mantle has a more sophisticated function than we expected," said Hirose, who was not involved in the current study. "The colorful mantle reflects useless light for photosynthesis (green and yellow) and scatters useful light (red and blue) forward, and laterally, into deep tissue."

The giant clams' colorful and sparkly sheen may one day inspire new forms of clean technology, the researchers said. For instance, traditional solar cells work well in direct sunlight, but not when they get too hot. With the clam's design, a reflective sheen could help solar cells stay cool even when they're exposed to intense sunlight, Sweeney said.

The study was published yesterday (Sept. 30) in the Journal of the Royal Society Interface.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

The Arctic's shrinking sea ice is reshaping the region's food web from the bottom up, a new study reports.

Historically, tiny plantlike organisms called phytoplankton burst into bloom in the spring in the Arctic Ocean. The enormous one- to two-week bloom sets off a feeding frenzy among zooplankton, fish and bottom-dwelling creatures at the base of the Arctic food chain.

"The entire ocean system is linked to this massive input of carbon," said lead study author Mathieu Ardyna, a marine biologist at Laval University's Takuvik Joint International Laboratory in Quebec, Canada. [On Ice: Stunning Images of the Canadian Arctic]

But now, because of the declining sea ice, a second bloom also appears in the fall, according to a new analysis of satellite records, published Sept. 2 in the journal Geophysical Research Letters. The fall bloom could have widespread ripple effects on marine life and the Arctic climate. Phytoplankton clear carbon dioxide from the atmosphere through photosynthesis.

Annual spring and fall phytoplankton blooms are a common feature in warmer oceans, from the cool north Atlantic to the hot, tropical Pacific. The vivid green, red and white swirls of these blooms paint the ocean like a Van Gogh sky.

Ardyna said the double Arctic blooms may herald a shift from a polar to a more temperate ecosystem.

However, the trends are so new, and varied across the Arctic, that the researchers can only speculate what the final impact will be. "For sure, the carbon cycling will change a little bit, but the question now is to understand how the rest of the plankton and fish will respond to this new pulse of phytoplankton," Ardyna told Live Science.

Ardyna and his co-authors charted phytoplankton blooms between 1998 and 2012 with satellite data that measures ocean color (a proxy for phytoplankton levels). The researchers also looked at sea ice extent and wind speeds.

The results showed that fall plankton explosions are becoming more frequent throughout the Arctic Ocean up to 80 degrees north latitude. At these high latitudes, there are no plankton blooms at all because of permanent sea ice.

The largest increases were seen in the Eastern Arctic Ocean, especially north of Russia, where ice once prevented plankton blooms. "The percentage change is really high here because this is where there used to be ice," Ardyna said. The western Arctic includes Alaska and Canada, while the eastern Arctic encompasses northern Europe and Russia.

The researchers said the plankton is likely thriving in fall for two reasons: delayed freezing and strong winds. In the fall, new sea ice starts to form when ocean temperatures fall below about 29 degrees Fahrenheit (minus 1.9 degrees Celsius). But as the Arctic sea ice shrinks, the ocean absorbs more of the sun's heat in summer, postponing the freeze until all the warmth dissipates. There were also a greater number of strong fall storms in the last decade, which can stir up nutrients to feed a phytoplankton bloom.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Gobs of microscopic organisms called algae may have met their match in viruses that can invade their cells, ultimately leading to death, new research suggests.

The findings may help researchers refine models that forecast algal blooms and the influence these microscopic plants have on the climate, experts say.

Algae, also known as phytoplankton, are at the bottom of the food chain and can multiply into blooms spanning thousands of miles at sea. They also carry out about half of all photosynthesis on the planet, relying on pigments like chlorophyll to capture the sun's energy and, during the process that involves carbon dioxide, turning that energy into sugars. The byproduct of the process is oxygen. [Earth from Above: 101 Stunning Images from Orbit]

"They are the foundation of the entire life at sea," said the study's co-principal investigator Ilan Koren, an associate professor of earth and planetary sciences at the Weizmann Institute of Science in Israel. "There is no life without these algal blooms."

Using satellite images, the researchers examined algae blooms and their chlorophyll concentrations from space. They focused on an algae patch in the North Atlantic that usually blooms in the spring (in the Southern Hemisphere, algae typically blooms in the fall and winter).

But satellite imagery can tell scientists only so much. It can show whether an algae patch has a decreased concentration of chlorophyll, but it doesn't explain why, Koren said.

He and his colleagues traveled to a circular 19-mile-wide (30 kilometers) bloom on a cruise to Iceland to take samples of coccolithophore algae known as Emiliania huxleyi. Viruses that kill the algae in boom-and-bust cycles, they found, were widespread in the samples. Evidence also suggested that the algae cells broke down in a way that is indicative of a viral infection.

Researchers have hypothesized that viruses probably control the proliferation of blooms, but this is the first study to show satellite evidence that viruses contribute to the demise of algal blooms, said Steven Wilhelm, a professor of microbiology at the University of Tennessee in Knoxville, who was not involved in the study.

"We've been studying [marine] viruses now since about 1990, when they re-emerged as being important," Wilhelm told Live Science. "Twenty-five years later, many of our ideas and hypotheses are being proven by really solid research efforts like this one."

Several factors can influence a bloom's well-being, including available sunlight and surrounding grazers such as zooplankton that eat the algae, Koren said. Many algae also thrive if the first 32 to 65 feet (10 to 20 meters) of the ocean are well stratified from deeper, colder layers of water where there is less light for photosynthesizing.

But if all of these conditions are stable, then biological processes, such as viral infections, may account for the decline of an algal bloom, Koren said.

"This is a huge step toward understanding the ecology in its natural scale," Koren added.

The North Atlantic bloom they examined likely converted 24,000 tons of carbon dioxide from the atmosphere, a weight equivalent to 120 blue whales, the largest animals on Earth. The algae converted the carbon dioxide into energy-providing organic carbons in a process called carbon fixation. (Phytoplankton must "fix" carbon before it can use it during photosynthesis.) Within one week, two-thirds of that carbon turned over as the bloom quickly grew and then expired.

What happens to carbon when an algal bloom dies has tantalized scientists for decades. It's unknown if it sinks into the ocean when the algae die, or if it gets released into the atmosphere as a contributor of global warming.

"People who are interested in global carbon cycling are very interested in this process," Wilhelmsaid.

The study doesn't answer this question, but it brings researchers a step closer to understanding what factors regulate algal blooms, Wilhelm told Live Science.

The lab of Assaf Vardi, assistant professor of plant sciences at the Weizmann Institute of Science, also contributed to the research. The study was published today (Aug. 21) in the journal Current Biology.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

Bacteria living in the warm waters off the Bahama Islands may feed on the mineral-rich dust that the wind carries over from the Sahara Desert, a new study finds.

Winds may blow the dust about 5,000 miles (8,000 kilometers) across the Sahara and the Atlantic Ocean before it settles along the Great Bahama Bank, a raised limestone platform on the ocean floor near the islands, the study reports.

The dust is rich in iron and manganese, elements that helped the researchers map the dust's journey. Scientists measured the amounts of these metals in 270 seafloor samples from the Great Bahama Bank over a three-year period. The areas west of Andros Island, the largest island in the Bahamas, had the highest concentrations of the elements. [7 Crazy Facts About Dust Storms]

Andros Island also has a large concentration of "whitings," stretches of milky-white water created by cyanobacteria that get their energy from the sun through a chemical process called photosynthesis.

"Cyanobacteria need 10 times more iron than other photosynthesizers, because they fix atmospheric nitrogen," Peter Swart, lead author of the study and chair of Marine Geosciences at the University of Miami, said in a statement. "Fixing nitrogen" refers to the process in which organisms capture nitrogen gas from the atmosphere and convert it into a useful form.

The result of this nitrogen fixation? "This process draws down the carbon dioxide and induces the precipitation of calcium carbonate, thus causing the whiting," Swart said.

Swart and his colleagues suggest that the iron-rich dust from the Sahara helped build the Great Bahama Bank by feeding the cyanobacteria. Over the past 100 million years, the wind-swept sedimentation may have fueled cyanobacteria blooms that turned the water white by creating carbonate whitings, the researchers said.

The study is published in the August issue of the journal Geology.

Follow Laura Geggel on Twitter @LauraGeggel and Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.

This Behind the Scenes article was provided to Live Science in partnership with the National Science Foundation.

Every organism on Earth, from microbes to plants to large predators, has evolved unique survival mechanisms and distinct ecological roles. For decades, the National Science Foundation (NSF) has funded basic research on how these varied organisms — the Earth's biodiversity — functions.

Some of this research has serendipitously yielded unforeseen discoveries that provide important societal benefits. Many of these discoveries would probably not have been produced through mechanisms other than basic research.

For example, recent findings about how geckos climb vertical walls and walk across ceilings led to the development of new adhesives as well as wall-climbing robots that may one day be used to, for example, produce gravity-defying climbing boots and help collect space junk.

Kellar Autumn of Lewis & Clark College, who helped characterize the nanophysics of the gecko's Spider Man-like abilities, said, "Geckos, which evolved 160 million years ago, are so novel that engineers would never have developed nano-adhesive structures without them. It took 15 years and lots of NSF support to understand the basic physical principles of gecko adhesion and then to apply them to make them work. This suggests that there is a library of biodiversity that can be mined for valuable uses if we have enough resources and enough time — in light of high extinction rates — to really understand them." [10 Surprising Ways that Biodiversity Benefits the Economy]

The researchers depicted in Behind the Scenes articles have been supported by the National Science Foundation, the federal agency charged with funding basic research and education across all fields of science and engineering. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation. See the Behind the Scenes Archive.

Extremophile kick-starts new industries:

After the discovery of a bacterium that lives at extremely high temperatures in Yellowstone National Park’s hot springs, scientists extracted a heat-resistant enzyme that helps copy DNA. This enzyme was used to develop a lab technique for rapidly duplicating DNA with the help of repeated heating and cooling cycles. Known as the polymerase chain reaction (PCR), this technique enables DNA fingerprinting, an essential forensics tool, and much of the biotechnology industry, worth more than $95 billion today.

Unlikely microbes advance brain research:

By illuminating light-sensitive proteins that have been inserted into a brain neuron (depicted here), scientists are able to turn on the neuron; the technique is called optogenetics. Scientists in laboratories all over the world use optogenetics to turn target neurons on and off, thus helping to identify the neurons’ functions. One goal is appropriate treatment targets for brain diseases ) — including schizophrenia and Parkinson’s, disorders such as anxiety, and traumatic brain injuries — which cumulatively cost the U.S. many billions of dollars annually. The development of optogenetics was made possible by earlier research on light-sensitive proteins in two microbes that don’t even have brains: an extremophile from super salty Saharan lakes and a common algae. Learn more here, here and here.

Geckos inspire more than car insurance:

Geckos can scamper up vertical walls and across ceilings because their feet have billions of tiny fibers that contact surfaces closely enough to form intermolecular bonds with them. The cumulative power of these fibers holds the foot in place. Made from tiny synthetic hairs that function like gecko bristles, gecko-inspired adhesives offer up to 100 times the gecko’s gripping power, and can be easily attached and detached from surfaces if manipulated correctly. Such adhesives may be used to improve medical equipment, climbing shoes and cell phones.

Walking in the gecko’s footsteps:

Wall-climbing robots are specially designed to walk and climb with gecko-inspired adhesives affixed to the bottom of their feet so that they can easily attach and detach their feet as they move. Potential applications for such robots include climbing on space structures, positioning sensors on high walls for monitoring air pollution, participating in search-and-rescue missions and finding cracks in bridges. Learn more here. Robots inspired by animals and insects represent the next wave of robotics. Why? Because of new ultra-sensitive tools for analyzing how organisms move and new materials for building bio-inspired robots that are resilient and tough enough to perform under real-world conditions.

Preventing bees from buzzing off:

Honeybees pollinate about $20 billion worth of U.S. farm products. But honeybee populations are threatened by factors including colony collapse disorder--the sudden disappearance and death of adults from hives. Marla Spivak of the University of Minnesota, shown here with a bee beard (Don’t try this at home!), is researching bee health to help combat these declines and “get bees back on their own six feet.” Learn more here.

Feeding and fueling the world:

Photosynthesizing organisms use sunlight and CO2 to produce sugars and oxygen. But photosynthesis is relatively inefficient. Nevertheless, some species of plants, algae and bacteria have evolved efficiency-boosting mechanisms that reduce energy loss or enhance CO2 delivery to cells during photosynthesis. Scientists are working to improve, combine and engineer such mechanisms. Their goal: to confer efficiency-boosting mechanisms on important crops to increase food production or possibly biofuels production.

Bats are farmers’ friends:

By eating insects, bats annually reduce pesticide costs for U.S. farmers by more than $22 billion. Bats are also essential pollinators of commercially valuable crops, including bananas. But a new, fast-spreading incurable disease — white nose syndrome — threatens the survival of some species. Researchers are racing to identify factors that promote disease susceptibility — information that could support management efforts. (Also note that the development of sonar for ships and ultrasound was partly inspired by bat echolocation--the navigation system used by most bats to find and follow quick-moving insect prey at night without crashing into trees or buildings.) Learn more here.

We need even “pesky” insects:

Research shows that, through evolution, evening primroses grown in insecticide-treated plots quickly lose defensive traits, such as their production of insect-deterring chemicals, which they no longer need in the absence of insects. The message: A loss of insects may yield unwelcome consequences such as the rapid loss of traits we value in plants, such as their good taste, which may have originally evolved to fight insects. Learn more here.

Are species losses sickening?

Studies show that loss of biodiversity harms the health of humans and other animals. Such studies yield information that is important for predicting and controlling many infectious diseases. For example, Lyme disease, primarily carried by white-footed mice, is transmitted to humans by ticks that become infected after biting a carrier. Studies indicate that when forests are degraded, mice thrive in the absence of their predators (which have disappeared from degraded forests). Furthermore, tick-eating opossums also vanish from degraded forests, so encounters between people and infected ticks become more likely. With about 300,000 Lyme diagnoses in the U.S. annually, the disease costs the nation billions of dollars annually. Learn more here and here.

Fighting invaders:

Since fire ants were introduced into the U.S. in the 1930s, they have been wreaking havoc. They now annually cause $5 billion in damages to agricultural and recreational resources by damaging farming fields and equipment with their nests and injuring people and animals with their painful stings. Because standard insecticides have not stopped them, researchers are taking new approaches. They recently identified genes that underlie social structure and communication within fire ant colonies. This will allow for the development of tools that would help destroy fire ant colonies by disrupting the chemical signals these insects use to communicate. Learn more here.

Today's climate change doesn't hold a candle to the chemical warfare waged on Earth more than 2 billion years ago.

Before plants discovered the power of photosynthesis, single-celled life survived on chemicals, not sunlight, burning through hydrogen, methane and sulfur, among other yummy compounds. These "anaerobes" that live without oxygen were poisoned when blue-green algae called cyanobacteria evolved photosynthesis and started exhaling oxygen. The highly reactive gas combines with metals and proteins in anaerobic cells, killing them. But cyanobacteria thrived, turning sunlight into sugar and excreting oxygen as waste.

Oxygen levels in rocks suddenly rise starting 2.5 billion years ago — a spike called the "Great Oxidation Event." The jump was long held up as evidence for when cyanobacteria evolved photosynthesis. But a study published today (March 23) in the journal Nature Geoscience joins a growing body of data that suggests the earliest sun-lovers appeared long before this oxygen spike. [7 Theories on the Origin of Life]

Many researchers now think the first photosynthetic organisms lived on Earth 3 billion years ago. And like art restorers who find a hidden image under an Old Master painting, these scientists are discovering a new picture of Earth's first breath.

Heavy metals

In the new study, Yale University geochemist Noah Planavsky and his colleagues analyzed levels of molybdenum and iron in 2.95-billion-year-old rocks from South Africa. The rocks were laid down in water, in a shallow ocean setting near the shore. The metals serve as markers of photosynthesis. Molybdenum isotopes, or elements with the same number of protons but a different number of neutrons, track manganese oxidization, a process that requires high levels of oxygen, Planavsky said.

The chemical traces in the rocks, from the Pongola Supergroup, indicate cyanobacteria were producing oxygen in ocean surface water, Planavsky said. "Our study is telling you that there was localized cyanobacteria production in the oceans," he told Live Science's Our Amazing Planet.

In another recent study, also on South Africa's Pongola rocks, scientists looked at chromium isotopes to estimate atmospheric oxygen levels 3 billion years ago. The results suggest atmospheric oxygen was about 100,000 times higher than could be explained by non-biological chemical reactions, according to the research, published Sept. 26, 2013, in the journal Nature.

"The two studies are quite complementary," Planavsky said. "We're providing independent evidence of the presence of cyanobacteria. We're tracking surface ocean processes and they're tracking terrestrial processes."

However, Woodward Fischer, a geobiologist at Caltech in Pasadena, Calif., cautions that the trace metal techniques need further validation. Both analytic methods are just about a decade old and are being tested in extremely old rocks. "The quality of our interpretations derived from them remains a little bit uncertain," said Fischer, who was not involved in either study. "In all fairness, we don't understand the molybdenum and the chromium cycle today."

Which came first?

As more sensitive techniques emerge for peering into deep time, a new debate has surfaced: Did microbes pump our planet's first breath, or did environmental changes push the planet into oxygen richness?

Emerging evidence suggests oxygen levels took a roller coaster ride in the 500 million years between when the first cyanobacteria evolved photosynthesis and the Great Oxidation Event. That's a long time for life — it's about the same as the time between Earth's first trilobites and humans.

Some researchers think Earth itself played a role in boosting oxygen levels as continents grew in size. Erosion of the crust and the changing nature of volcanoes — bigger continents mean more land-based eruptions spewing out gas into the atmosphere, rather than underwater blasts. These geologic shifts could have pushed Earth's atmosphere toward oxygen in concert with the cyanobacteria.

"What's really exciting about this is the relative role of biological evolution versus geological evolution in the major turning points in Earth's history," Planavsky said. "That's what's driving our research."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook and Google+. Original article at Live Science's Our Amazing Planet.

Researchers have begun engineering plants to produce more loads of energy or sense pollution and even explosives.

In a new study, researchers embedded tiny structures called carbon nanotubes into the energy-making factories of plants, increasing their light-capturing ability by 30 percent. Using other carbon nanotubes, the researchers made plants sensitive to the atmospheric pollutant nitric oxide.

"Plants are very attractive as a technology platform," Michael Strano, leader of the study detailed March 16 in the journal Nature Materials, said in a statement. "They repair themselves, they're environmentally stable outside, they survive in harsh environments, and they provide their own power source and water distribution," said Strano, a chemical engineer at MIT.

Strano and his colleagues are pioneering a new field they call "plant nanobionics." "Nano" refers to the scale of the materials, which are on the order of one-billionth of a meter, and "bionic" refers to the use of nature to inspire engineering. [Top 10 Emerging Environmental Technologies]

Super-powered plants

The researchers were originally working on building self-repairing solar cells based on plant cells, which convert light into chemical energy, in the form of sugars and other compounds, by a process known as photosynthesis. The process relies on chloroplasts, the tiny energy factories inside plant cells.

Strano and his team wanted to isolate chloroplasts from plants and make them more efficient. But if chloroplasts are removed from plants, they start to degrade after a few hours due to light and oxygen damage.

To protect chloroplasts against this damage, the researchers embedded the chloroplasts with tiny antioxidant particles, or nanoparticles, which scoop up oxygen radicals and other highly reactive molecules. In order to deliver the nanoparticles, the researchers coated them in a highly charged molecule that allowed the particles to penetrate the fatty membranes of the chloroplasts. As a result of the nanoparticles, the amount of damaging molecules plummeted.

Next, the researchers coated tiny cylinders called carbon nanotubes in negatively charged DNA and embedded them in the chloroplasts. The nanotubes worked like artificial antennae that allowed the plant to capture more light than usual.

The rate of photosynthesis in the chloroplasts with embedded nanotubes was almost 50 percent greater than in isolated chloroplasts that lacked the nanotubes. When the researchers embedded both antioxidant nanoparticles and carbon nanotubes in the chloroplasts, these cells continued to function outside of the plant for even longer.

The researchers also improved the energy efficiency of living plants. They infused nanoparticles into a small flowering plant called Arabidopsis thaliana, improving photosynthesis by 30 percent. What effect, if any, this has on the plant's sugar production is a mystery, the researchers said.

Pollution sensors

Strano and his colleagues also found a way to turn the Arabidopsis thaliana plants into chemical sensors, using carbon nanotubes that detect the pollutant nitric oxide, which is produced by combustion.

The researchers have previously developed carbon nanotubes that detect the explosive TNT and the nerve gas sarin, so they might be able to turn plants into sensors to detect these toxins at low concentrations. Nanobionic plants could also be used to monitor pesticides, fungal infections or bacterial toxins. In addition, the team is now working on incorporating electronic materials into plants.

Follow Tanya Lewis on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Corals live in symbiosis with their algal tenants — algae provide corals with carbohydrates, oxygen and energy, while corals shelter algae and feed them nutritious waste products, such as carbon dioxide. Driving this mutually beneficial relationship is sunlight, which the algae use to produce oxygen and other nutrients in a process called photosynthesis.

New research published today (Feb. 12) in the Journal of Experimental Biology shows that corals play a vital role in making sure their algae friends get the sunlight they require.

Using light sensors, scientists have determined that coral tissue traps and redistributes light over the coral colony. This transmitted light increases the algae's photosynthesis, resulting in more oxygen for the coral. What's more, the wavelengths of light that the tissues scatter the most are those that the algae use best. 

"Most of the scattering is in the shorter wavelengths, and this overlaps with the algae's photopigment absorption," said study author Daniel Wangpraseurt, an aquatic ecology Ph.D. student at Australia's University of Technology, Sydney. "The relationship is quite smart."

Scattering light

Previous studies investigating how corals redistribute light have focused on dead coral skeletons, Wangpraseurt told Live Science. In 2005, researchers found that coral skeletons highly reflect light in all directions. More recently, scientists learned that the light reflectance of coral skeletons is highly variable — some species are much poorer at scattering light than others.

Until now, researchers thought that coral tissue didn't redistribute light like coral skeletons do. They assumed that the tissue's refractive index — a measurement of how much light slows down and bends when traveling between mediums — was the same as water. This would mean, essentially, that the light's trajectory wouldn't change much, if at all, as it traveled from seawater through coral tissue.

But in 2012, Wangpraseurt and his colleagues discovered that the amount of light present in the lower and upper layers of coral tissue isn't the same. Looking into the scientific literature, they also found that certain layers of tissues are high in protein, which could potentially affect the refractive index and result in light scattering.

To find out if coral tissue really can trap and retransmit light, the researchers collected healthy brain corals from the Heron Island Research Station on the Great Barrier Reef. While shining near-infrared laser light or red laser light onto the coral samples, they inserted light microsensors into the coral tissues to see how far the light propagated vertically and horizontally. [Images: Colorful Corals of the Great Barrier Reef]

They detected both the red and near-infrared light as far away as 0.8 inches (20 millimeters) from the tissue area directly illuminated by the laser beams. Closer examination of the light distribution suggested that the near-infrared light, which the algae don't use for photosynthesis, actually passed right through the coral tissue — the coral skeleton reflected the light back to the animal's tissue. On the other hand, the tissue did trap and laterally transport the red light, which the algae's photopigments absorb for photosynthesis.

Improving photosynthesis

To see if the algae actually made use of the scattered light, the team repeated the experiment with a different microprobe. "We exchanged the light sensor for an oxygen sensor," Wangpraseurt said. Flicking the red light on and off resulted in rapid increases and decreases in oxygen concentrations in areas up to about a centimeter (0.4 inches) from the laser beam. That is, the scattered light improved the algae's overall photosynthesis.

The researchers also used a fluorescent imaging technique to see if the algae could use the redistributed light (during photosynthesis, the light-absorbing chlorophyll molecules in plants fluoresce, or re-emit some light). The team shone red, green and violet light onto the coral tissues, and found that each of the colors caused the algae to fluoresce strongly up to 6 mm (0.24 inches) from the laser beam. 

Interestingly, corals can control the amount of light that gets scattered, the researchers found. In low light conditions, coral tissues expand, allowing more light to scatter; when faced with a lot of light, they contract and reduce the light propagation.

"They are able to reorganize the light exposure to their algae more than we previously thought," Wangpraseurt said. This ability may help the corals protect themselves and their symbionts from light-induced stress, which is known to cause coral bleaching.

Follow Joseph Castro on Twitter. Follow us @livescience, Facebook & Google+. Original article on Live Science.

Tiny marine organisms that are thought to play a crucial role in the planet's carbon and nutrient cycles are mysteriously shedding massive amounts of bacterial "buds," loaded with proteins and genetic information, into the world's oceans, according to a new study.

These so-called vesicles are spherical pouches containing DNA, carbon and nutrients that are being continually produced and released by Prochlorococcus, the most abundant type of cyanobacteria, which are miniscule photosynthesizing cells in the ocean that convert sunlight and carbon dioxide into oxygen and organic carbon. This puzzling discovery, reported online today (Jan. 9) in the journal Science, could lead to a new understanding of how carbon moves through the oceans, and possibly how genetic information is swapped between marine organisms, the researchers said.

Prochlorococcus is dominant in all of the world's open oceans, except at high latitudes, where the water is very cold, said Steve Biller, a postdoctoral researcher at MIT in Cambridge, Mass., and lead author of the new study. The oxygen exhaled by these photosynthesizing microbes helps nourish other organisms in the marine environment. [Extreme Life on Earth: 8 Bizarre Creatures]

"They're doing roughly 10 percent of all photosynthesis on the planet, so they play an important role at the base of the food web of the world's oceans," Biller told LiveScience.

The marine ecosystem

Biller began studying this type of cyanobacteria at MIT after a previous graduate student in his lab examined Prochlorococcus under a powerful electron microscope and was baffled by the presence of small, pimple-type specks around the cells.

"It was complete serendipity," said study co-author Sallie Chisholm, a professor of biology at MIT. "Anytime anyone new joined the lab, I would say, 'What do you think these are?' When Steve joined, he had classical training in microbiology, and thought they might be vesicles."

Other types of bacteria, such as E. coli, were previously known to produce vesicles, but this is the first time photosynthetic cells in the ocean have been shown to produce such extracellular structures, Chisholm said.

The vesicles were detected in laboratory cultures of cyanobacteria, and in samples of seawater taken from the nutrient-rich waters off the coast of New England and the more nutrient-sparse waters of the Sargasso Sea, a region in the middle of the North Atlantic Ocean.

The vesicles from the seawater were found to contain DNA from different types of bacteria — a discovery that suggests many other ocean microbes also may be capable of producing vesicles, Biller said. Furthermore, the researchers found that vesicles were being produced rapidly.

"We show that two to five vesicles are produced per cell per generation," Chisholm said. "This means that every time the cell divides into two, it produces two to five of these things. If you extrapolate that to global production, based on the growth rates of Prochlorococcus in the wild, it's a huge amount that they're shedding and putting out into the seawater." [50 Amazing Facts About Earth]

Biller estimates Prochlorococcus alone is releasing about a billion-billon-billion (a billion times a billion times a billion) vesicles per day, representing huge pools of carbon in the open oceans. Typically, bacteria grow to a certain size and then reproduce by dividing into two or more parts — a biological process known as fission. Under suitable conditions, bacteria can divide rapidly, with some populations capable of doubling in less than 10 minutes.

"It adds a whole other dimension to parts of the ocean that we need to better understand," Biller said. "For one, figuring out how carbon moves through the ocean has been something of a black box for a number of years. The idea that this could be a new mechanism for how some portion of that carbon moves around is pretty important."

An ocean of mysteries

Yet the discovery raises as many questions as it answers, he added. Most puzzling is why cyanobacteria would produce vesicles in the first place.

"If you have an organism eking out a living in a really dilute environment, where nutrients are extremely low, why would it cast things off into the environment that would limit its own growth?" Chisholm said. "We figure these vesicles have to have some important function."

Research in this area is preliminary, but the scientists have some intriguing hypotheses. For example, since the vesicles contain DNA, they could play a role in transferring genes and developing genetic diversity among populations of cyanobacteria in the oceans.

"They could be moving genetic information between cells in the ocean," Biller said. "We've also talked a little about their potential roles in helping to move nutrients around within the microbial food web. But the magnitude of these benefits to the cell is still beyond our understanding."

Other ideas include the production of vesicles as a defense mechanism against predators. Viruses have been shown to attach themselves to vesicles, injecting their DNA into the spherical structures. This effectively prevents the virus from being able to reproduce in a living cell.

As such, cyanobacteria could be deploying vesicles to use as decoys to deflect attacking viruses, said David Scanlan, a professor of marine microbiology at the University of Warwick in the United Kingdom. Scanlan, who was not involved in the new study, penned an accompanying editorial in the journal Science about the implications of the findings.

"It would be like thinking of these vesicles as anti-aircraft chaffs that planes use as decoys against missiles," Scanlan told LiveScience.

Moving forward

Yet, it is still unclear how these vesicles are produced and, in particular, how they come to contain genetic information, which is found in a cell's nuclei and mitochondria.

"If these vesicles are just budding off the outside of the cell, it's not really clear how DNA gets into them," Scanlan said. "It could be an interesting, and potentially novel, angle on how DNA and RNA can be moved between organisms."

In cells, RNA is a single-stranded molecule involved in the coding, regulation and expression of genes. Among its myriad functions, RNA works as an on-and-off switch for some genes.

Biller and his colleagues plan to investigate some of these ideas, but studying such tiny organisms remains challenging.

"It took about three years to get to this point, and it could take another five years to figure out why Prochlorococcus might be doing this," Chisholm said.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.

(ISNS) -- Sunlight drives nearly all life on Earth, and scientists want to develop ways for it to power civilization as well. Now researchers suggest that a relatively simple, biologically inspired technique for harvesting sunlight could in principle convert the sun's rays to electricity very efficiently.

In solar cells, molecules absorb photons, or packets of light energy, and give off electrons to generate an electrical current. However, these electrons can quickly combine with other charged particles, and get absorbed, causing the cells to lose efficiency. As the electrons are absorbed, the amount of electricity flowing through the cell is reduced.

On the other hand, the light-harvesting molecules that plants, bacteria and algae use in photosynthesis can convert light to electrical energy with nearly perfect efficiency under some conditions. This remarkable performance is impossible in classical physics — instead, experiments suggest it may be due to strange effects often seen in quantum physics. For instance, in quantum physics, particles such as electrons can essentially each be in more than one place at the same time or spin in two opposite directions simultaneously, a bizarre phenomenon known as superposition.

"It was very surprising to discover that biological systems like plants are actually using quantum mechanics to do things like photosynthesis," said researcher Andy Parker, a physicist at the University of Cambridge in England.

Scientists worldwide are investigating how photosynthesis works on a quantum level to design better solar cells. Now Parker and his colleagues have devised a relatively simple way for quantum effects to potentially significantly enhance artificial light-harvesting devices.

"We'd like to come up with a system that really can be built," Parker said. "We want to help address the energy crisis."

The researchers modeled a system made up of three molecules exposed to light, mimicking the architecture and molecular components seen in the photosynthetic pigments of plants. This scenario consists of two "donor" molecules that emit electrons after they absorb photons, and an "acceptor" molecule that receives the electrons given off by the donor molecules.

The scientists reasoned the donor molecules can interact with each other through their electromagnetic fields. "Atoms in the donor molecules have electrons around them, and those electrons can set up electromagnetic fields that the molecules can 'see' across the distance between them," Parker said. "It's a lot like how two magnets can 'see' each other across distances — if one is aligned one way, the other will tend to align the same way."

This interaction between the donor molecules leads them to share electrons. A strange principle of quantum physics then comes into play known as quantum interference, where particles such as electrons can behave like the waves seen rippling on the surfaces of ponds, interfering with each other in complex ways.

Quantum interference leads the donor molecules to both become good at absorbing light and bad at recombining with electrons they give off. Calculations suggest this system could generate 35 percent more current than a solar cell that works based on classical physics alone.

This model the researchers propose is simpler than some more exotic ones proposed for how photosynthesis works. "We're saying relatively straightforward effects can produce real benefits," Parker said.

"This is only a theoretical paper with a 'toy model,' yet it incorporates some nice ideas that may be advantageous for future molecular designs," said chemical physicist Elad Harel at Northwestern University in Evanston, Ill., who did not take part in this research.

Parker cautioned they are not saying this system is definitely how plants achieve such amazing efficiency with photosynthesis, but one element of what plants might do.

"The molecules involved in photosynthesis are really quite complicated, and we don't want to extrapolate from a few simple mechanisms to saying we completely understand a highly evolved system such as photosynthesis," Parker said.

The researchers add they have not actually built this system in real life yet. "However, we know there are molecules with these general properties that can be made in the lab, and we're talking with people who work in this area to come up with a system," Parker said.

Harel cautioned "the biggest problem is that these model systems are extremely difficult to synthesize." There may be many ways in which energy can get lost "that prevent the type of efficiencies reached by these schemes," Harel added. "In other words, real systems are much more complex."

More realistic simulations of actual systems are critical, Harel said. "What specific molecules will be used? What is their structure? How do they fluctuate and move at room temperature? Are they in solution or in a film?" Harel asked.

Parker and his colleagues detailed their findings Dec. 18 in the journal Physical Review Letters.

Inside Science News Service is supported by the American Institute of Physics. Charles Q. Choi is a freelance science writer based in New York City who has written for The New York Times, Scientific American, Wired, Science, Nature, and many other news outlets. He tweets at @cqchoi.

The game changer for life on Earth was photosynthesis. Now scientists think they've found a molecular stepping-stone for this complicated chemical process, which flooded the atmosphere with oxygen about 2.4 billion years ago.

Tiny single-celled organisms called cyanobacteria were the first life on Earth to master photosynthesis. They use light from the sun to split water molecules, releasing oxygen as waste. Many researchers suspect the oxidation of the element manganese by earlier life-forms was the first step in developing this molecular machinery — the metal still plays a critical role in photosynthesis today.

At its most basic, the process of oxidation removes electrons from atoms. In this case, the early microbes stole electrons from manganese, replacing them with oxygen taken from carbon dioxide. The result is manganese oxide, similar to iron rust or copper's green patina.

"If this happened, we would be able to see manganese [oxide] being concentrated in rocks before the rise of oxygen," said Woody Fischer, a geobiologist at Caltech in Pasadena, Calif., and study co-author.

Fischer and his colleagues searched for manganese-rich rocks deposited just before the Great Oxidation Event, when photosynthesis began and Earth's atmosphere flooded with oxygen. (Genetic studies that look at the evolution of proteins and enzymes in photosynthesizing microbes also match this timing.)

In 2.415-billion-year-old rocks from South Africa, the researchers found their smoking gun — rich deposits of oxidized manganese. The ancient rock is evidence that microbes were harnessing the sun for energy and converting it to food with manganese, according to a study published June 24 in the journal Proceedings of the National Academy of Sciences.

Chemical analysis of the rock, part of an ancient ocean basin, also reveals no atmospheric oxygen was available, so the water-splitting cyanobacteria had yet to evolve. (However, oxygen was present in molecules of water and carbon dioxide, for example.)

The cyanobacteria may have adopted or improved on the manganese process for photosynthesis, the researchers think. "The manganese is the magic machinery that splits water molecules," Fischer said.

The team now plans to try to reverse-engineer modern cyanobacteria to perform manganese-oxidizing photosynthesis, and look at rocks of the same age on other continents to back up their finding.

"Manganese plays an essential role in modern biological water-splitting as a necessary catalyst in the process, so manganese-oxidizing photosynthesis makes sense as a potential transitional photosystem," Jena Johnson, a graduate student at Caltech and lead author of the study, said in a statement.

Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook & Google+. Original article on LiveScience.com.

Humans can't teleport or reside in multiple places at once — but the tiniest particles of matter can.

These eerie quantum effects have traditionally been studied and observed only under the strictly controlled conditions of a physics lab. That is, until some scientists suggested that such weirdness also exists in wet and soggy biological systems.

In recent years, this hypothesis has gained more and more support, with a new study detailed in the journal Science suggesting plants may rely on such physics to survive. [The 9 Biggest Unsolved Mysteries in Physics]

The most efficient path

Plants are able to harvest as much as 95 percent of the sunlight they soak up, instantly converting this solar energy into chemical energy, in 1 million billionth of a second, in a process called photosynthesis.

The new Science study on purple bacteria, which also photosynthesize, gives more support to the idea that plants use quantum mechanics to achieve this near-perfect efficiency. A trick of quantum physics called coherence, the researchers suggest, helps the energy of the elementary particles of light, called photons, find the most efficient path to a plant's (or purple bacterium's) so-called reaction center, where the light's energy fuels the reaction that produces carbohydrates.

On a physical system, coherence could be illustrated with a pair of pendulums that continuously transfer energy from one to the other, backward and forward, in a coherent, cyclic mode.

When a photon excites molecules inside a cell, the energy does not hop through the system, but follows different energy pathways at once, simultaneously searching for the most efficient way into the reaction center where the chemical reaction actually takes place.

This is known as the quantum principle of superposition, or being in many different places at the same time.

Quantum effects in nature

Coherence has been suspected and experimented with in living systems before, when researchers fired extremely short but intense laser pulses at multiple molecules of a photosynthetic organism — a purple bacterium called Rhodopseudomonas acidophila that applies the exact same principles of light harvesting to survive as plants do — and tracked the flow of energy through its system. [Twisted Physics: 7 Mind-Blowing Findings]

The latest research, led by Niek van Hulst of the Institute of Photonic Sciences in Castelldefels, Spain, went a step further.

"Previous studies have done experiments where they had millions of molecules in the same volume that they were measuring," co-author of the new study, Richard Cogdell of the University of Glasgow, told LiveScience.

"The quantum effects could be seen, but they were rather weak. And we never knew whether it was because they are weak or because each of the individual molecules was slightly out of phase with each other so they interfered in a way that you did not see the coherences of quantum behavior."

For the new tests, the scientists used purple bacteria once again, but this time shot laser flashes at a single molecule instead of using many molecules at once.

The light-harvesting complexes of the bacteria are arranged in a pattern of adjacent rings, or molecules that make up one light-harvesting complex. In the organism, the rings pack together, but the researchers isolated individual rings, and put them outside of the bacterium, on a surface. When a photon comes into contact with an isolated ring, some of it gets emitted as fluorescence — a form of natural luminescence —which is essentially the spontaneous transfer of energy from a high-energy level to a lower-energy level.

The researchers noticed that the amount of fluorescence didn't stay constant: It kept rising and falling, "oscillating between the high state and a low state, which is this coherent oscillation," said Cogdell.

That oscillation suggests the laser light was able to find the most efficient energy pathway to the reaction center almost instantaneously — despite the highly variable conditions of a biological system. 

"This sort of coherences have been seen in physical systems before, but only at very low temperature and very well-defined controlled conditions," Cogdell said. "The surprise is that you can see these effects in wet, messy biological systems at room temperature. That's the remarkable finding, that you can find it in biology."

Greg Engel, a chemistry professor at the University of Chicago, who was not involved in the study, told LiveScience that the most exciting element of the research was "pulling back the curtain" and learning how photosynthetic energy transfer really works. "The authors point us toward new design principles for controlling the flow of energy through molecular systems," Engel said.

Once it is clear what factors affect the frequency of the coherence and whether it is possible to vary it, the findings could lead to boosting the efficiency of the light-harvesting process, said Cogdell.

And that achievement could pave the way to much more efficient photovoltaic cells to generate electricity, with the help of artificial photosynthesis, mimicking the extra-efficient process possibly happening in every single, tender green leaf.

Follow Katia Moskvitch on Twitter @SciTech_Cat. Follow us @livescience, Facebook & Google+. Original article on Live Science.