We have been on a years-long campaign of satellite remote sensing of the vast desert landscapes in Eastern Sudan.

This involved using satellite aerial imagery to systematically and painstakingly search for archaeological features in Atbai Desert of Eastern Sudan, a small part of the much larger Sahara.

Our team — which includes archaeologists from Macquarie University, France's HiSoMA research unit, and the Polish Academy of Sciences — wanted to tell the story of this desert region between the Nile and the Red Sea, without having to excavate.

One mysterious archaeological feature stood out. We kept finding large, circular mass graves filled with the bones of people and animals, often carefully arranged around a key person at the center.

Likely built around the fourth and third millennia BCE, all these "enclosure burial" monuments have a large round enclosure wall, some up to 80 meters [262 feet] in diameter, with humans and their cattle, sheep and goats buried inside.

Our new research, published in the journal African Archaeological Review, reveals how we found 260 previously unknown enclosure burials east of the Nile River, across almost 1,000km of desert.

Who built them?

Already known from a few excavated examples in the Egyptian and Sudanese deserts, these large circular burial monuments have long puzzled scholars.

What seemed once isolated examples emerge now as a consistent pattern. It is suggestive of a common nomadic culture stretching across a vast stretch of desert.

Most are within the borders of modern Sudan on the slopes of the Red Sea Hills. Unfortunately, satellite imagery alone cannot communicate the whole story of these enclosure burial builders.

The carbon dates and pottery from the few excavated monuments tell us these people lived roughly 4000–3000 BCE, just before Egyptians formed a territorial kingdom we know of as Pharaonic Egypt.

But these "enclosure burial" nomads had little to do with urbane and farming Egyptians.

Living in the desert and raising herds, these were Saharan desert nomads through and through.

A new elite?

Some enclosures show "secondary" burials arranged around a "primary" burial of a person at the center —perhaps a chief or other important member of the community.

For archaeologists, this is important data for discerning class and hierarchy in prehistoric societies.

The question of when Saharan nomads became less egalitarian has plagued archaeologists for decades, but most agree it was around this time of the fourth millennium BCE that a distinctive "elite" class emerged.

This is still a far cry from the sort of huge divisions between ruler and ruled as seen in societies such as Egypt, with its pharaohs and farmers. However, it ushers in the first traces of inequality.

Animals held in high esteem

Cattle seem very important to these prehistoric nomads (a theory also supported by ancient local rock art in the area).

Burying themselves alongside their herd, these nomads show they held their animals in esteem.

Thousands of years later, local nomads chose to reuse these now "ancient" enclosures for their burial plots — sometimes almost 4,000 years after they were first built.

In other words, the prehistoric nomads created cemetery spaces that lasted for millennia.

What happened to these people?

No one can say for sure.

The few dates we have for these monuments cluster between 4000–3000 BCE, nearing the end of a period when the once-greener Sahara was drying, a phase scientists call the "African Humid Period".

From north to south, the summer monsoon gradually retreated, reducing rainfall and shrinking pastures. This led nomads to abandon thirsty cattle, increase the mobility of their herds, migrate to the south or flee to the Nile.

The monuments are overwhelmingly located near what were then favorable watering spots; near rocky pools in valley floors, lakebeds and ephemeral rivers.

This tells us that when the monuments were being built, the desert was already quite challenging and dry.

At some point, as grass and bush made way for sand and rocks, keeping their prized cattle became unsustainable.

Having large herds of cattle in this desert, at this period, may have been a way of showing off an expensive and rare possession — a prehistoric nomad's equivalent to having a Ferrari. This may help explain why cattle were frequently buried alongside their owners in enclosure burial monuments.

A bigger story

These enclosure burials are only one part of the greater story of human adaptation to climate change across North Africa.

From the Central Sahara, to Kenya and Arabia, keeping cattle, goats and sheep transformed societies. It changed the food they ate, the way they moved around, and community hierarchies.

It's no coincidence communities changed how they buried their dead at the same time as they adopted herding lifestyles.

These burial enclosures tell us even scattered nomads were extremely well-organized people, and expert adapters.

Our discovery reshapes the story of the Sahara deserts and the prehistory of the Nile.

They provide a prologue for the monumentalism of the kingdoms of Egypt and Nubia, and an image of this region as more than pharaohs, pyramids and temples.

Sadly, many of these enclosure monuments are currently being destroyed or vandalized as a result of unregulated mining in the region. These unique burials have survived for millennia, but can disappear in less than a week.

Maria Gatto (Polish Academy of Sciences) was an author on our paper. We also want to acknowledge Alexander Carter, Tung Cheung, Kahn Emerson, Jessica Larkin, Stuart Hamilton and Ethan Simpson from Macquarie University for their contribution. We are also grateful to the National Corporation of Antiquities and Museums (Sudan).

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

This intriguing astronaut photo shows a trio of ancient "black mesas", which sit side-by-side in the Sahara desert. The dark structures have enabled a series of rare sand dunes to form around them while also creating a surprising "dune-free zone."

The three mesas, or flat-topped hills, are located around 8 miles (13 kilometers) northwest of the town of Guérou in southern Mauritania, which is home to around 22,000 people. The mesas are made from sandstone and rise steeply above the surrounding plains, reaching between 1,000 and 1,300 feet (300 and 400 meters) above the ground. The largest of the trio is approximately 6 miles (9.5 km) across at its widest point, while a fourth mesa is located just north of the trio, but is positioned just out of frame.

The dark color of these circular hills is the result of "rock varnish" — a black, clay-based coating, rich in manganese and iron oxides, that forms on exposed and arid rocks over thousands of years, according to NASA's Earth Observatory. This coating was likely partly fixed in place by microorganisms and is made up of multiple micrometer-thick laminations, according to Science Direct.

To the west of the mesas (on the left of the photo) is a barren rocky plain with a surprising lack of sand dunes. But to the east of the flattened hills, you can see several sizable dunes that are seemingly flowing away from the black rocks like a rippling tail.

There are two main types of sand dunes visible in the image. The first type are rare "climbing dunes," which are the larger, ridge-like piles of sand that have piled up along the mesas' eastern walls. The second type are "barchan dunes," which are more common and make up the mesas' stripy tail. In both cases, the dunes have a distinctive reddish-yellow hue.

The sand dunes only form on the eastern side of the mesas because the wind predominantly blows from that direction, carrying sand that then gets caught on the sloped elevations surrounding the black rocks.

Sand does not accumulate to the west of the mesas because of a phenomenon known as "wind scour," which results from superfast vortices within the wind that gets squeezed in between the mesas, which blow sand away from the flattened hills, according to the Earth Observatory.

Another astronaut photo, taken in 2014, shows this odd effect over a larger area (see below). In this shot, you can see the barchan dunes extend much further away from the mesas in the photo, as well as another larger mesa further east.

During the Paleozoic era, which lasted from 541 million to 251.9 million years ago, all these mesas were likely part of a single massive rock formation that has since been broken up by millennia of water and wind erosion, according to the Earth Observatory.

This formation may have been similar to the Richat Structure — a massive set of concentric rings of rock, also known as the "Eye of the Sahara," which is located in Mauritania around 285 miles (460 km) north of Guérou.

Mesas can be found across the globe but there is a particularly high concentration of them in the Sahara, as well as throughout parts of the U.S., such as Colorado, New Mexico, Utah, and Arizona, according to the National Park Service.

Elsewhere in the solar system, mesas are a prominent geological feature on Mars, having been carved out of the Red Planet by billions of years of wind erosion, according to Live Science's sister site Space.com.

For more incredible satellite photos and astronaut images, check out our Earth from space archives.

Whale Valley is a region of the Egyptian Sahara desert that is peppered with archaic whale skeletons, some of which have feet and toes preserved.

These skeletons and other marine fossils date to the late Eocene epoch (55.8 million to 33.9 million years ago), when present-day Egypt was submerged beneath the Tethys Ocean and whales had just evolved into sea creatures, according to UNESCO.

"These fossils represent one of the major stories of evolution: the emergence of the whale as an ocean-going mammal from a previous life as a land-based animal," UNESCO's website says.

Paleontologists have unearthed more than 400 ancient whale skeletons in Whale Valley since the beginning of the 20th century, according to a UNESCO video. The first such discovery, in 1902, uncovered a never-before-seen whale species called Basilosaurus isis (formerly Zeuglodon isis). This whale grew up to 60 feet (18 meters) long and probably dined on smaller whales, crushing their skulls before gulping them down, according to a 2019 study.

Evidence suggests B. isis "had a long snout and was armed with pointed incisors and sharp cheek teeth," Manja Voss, a marine mammal expert at the Berlin Museum of Natural History and the lead author of the 2019 study, previously told Live Science.

Related: Eye of the Sahara: Mauritania's giant rock dome that towers over the desert

Researchers have found scores of B. isis skeletons in Whale Valley, but in 1989, paleontologists made a remarkable discovery: A team from the University of Michigan and the Egyptian Geological Museum unearthed B. isis skeletons with hind limbs, feet and toes, according to a 2023 review article.

Modern-day whales lack hind limbs, but still have pelvic bones indicating that they once had them, according to the University of Hawaii. This means the fossils in Whale Valley are some of the oldest known archaeocetes, a group of mammals from the Eocene that later evolved into modern-day whales and dolphins, according to the 2023 review.

In 2005, paleontologists uncovered a stunningly preserved, near-complete B. isis skeleton, prompting UNESCO to list Whale Valley as a World Heritage site. Since then, plenty more fossils have emerged, including the remains of ancient Eocene turtles, bony fishes, sharks, rays, crocodiles, sea cows and shellfish, according to the review.

These fossils have stood the test of time thanks to the region's arid climate since the Pliocene (5.3 million to 2.6 million years ago), according to UNESCO.

Whale Valley operates as an open-air museum, complete with a visitor center and easy access for tourists, but the site is strictly protected. Researchers continue to find new fossils and learn more about the geology of the area, according to the review.

Discover more incredible places, where we highlight the fantastic history and science behind some of the most dramatic landscapes on Earth.

Two 7,000-year-old mummies belong to a previously unknown human lineage that remained isolated in North Africa for thousands of years, a new study finds.

The mummies are the remains of women who once lived in the "Green Sahara," also known as the African Humid Period. Between 14,500 and 5,000 years ago, the now-inhospitable Sahara was a humid and verdant savanna, home to humans who hunted and eventually herded animals alongside lakes and rivers.

DNA from the two mummies revealed that the never-before-seen North African lineage was distinct and isolated from populations living in sub-Saharan Africa around the same time. The findings, reported April 2 in the journal Nature, suggest there was little genetic exchange across the Green Sahara during this time, though some cultural practices may have spread through the region.

Between 2003 and 2006, archaeologists unearthed the remains of 15 individuals in the Takarkori rock shelter, located near the middle of the Sahara in what is now southwestern Libya. The site included evidence of human occupation and pastoralism, or herding, dating back more than 8,000 years. Of the 15 individuals, most of whom were women and children, two had naturally mummified, which helped preserve their DNA.

"We were very fortunate to have samples preserved at this level," study co-author Nada Salem, a paleogeneticist at the Max Planck Institute for Evolutionary Anthropology in Germany, told Science magazine. The region's high temperatures can quickly break down the DNA in human remains, leaving few examples of ancient DNA in the region.

A 2019 study examined mitochondrial DNA from the same remains. However, mitochondrial DNA, which is only inherited from the mother, doesn't provide as much information about population dynamics as DNA from chromosomes, which is inherited from both parents. To obtain this genome-wide data, the researchers extracted preserved DNA from the mummified remains and compared it with DNA from about 800 present-day individuals from Africa, the Near East and southern Europe, along with 117 ancient genomes from the same regions.

Related: Could the Sahara ever be green again?

The Takarkori individuals possessed genetic markers distinct from populations in sub-Saharan Africa, the team found, suggesting they were from a previously unknown and relatively isolated lineage that diverged from sub-Saharan African populations some 50,000 years ago. But the individuals did have some ancestors from the Levant, a stretch of land bordering the eastern Mediterranean Sea. The Takarkori DNA also showed traces of Neanderthal ancestry that could only have been acquired outside of Africa, as Neanderthals lived in Eurasia. But the mummies' genomes contained 10 times less Neanderthal DNA than those of people living outside of Africa today.

The findings suggest that the Green Sahara didn't act as a migration corridor between sub-Saharan Africa and northern Africa. However, archaeological evidence suggests that cultural exchange between the regions did occur.

"We know now that they were isolated in terms of genetics, but not in cultural terms," study co-author Savino di Lernia, an archaeologist at Sapienza University of Rome, told CNN. "There's a lot of networks that we know from several parts of the continent, because we have pottery coming from sub-Saharan Africa. We have pottery coming from the Nile Valley and the like."

The rise of pastoralism in the Sahara also likely arose from interactions with other groups that were raising domesticated animals at the time, rather than through large-scale migrations, the researchers suspected.

This isolated lineage no longer exists in its original form today, but at some point people from this lineage mingled with outsiders, which is why some people living in North Africa today have inherited pieces of this genetic heritage, the researchers found.

"By shedding light on the Sahara's deep past, we aim to increase our knowledge of human migrations, adaptations, and cultural evolution in this key region," di Lernia said in a statement.

This intriguing astronaut photo shows around a dozen giant "star dunes" as they slowly dance across a sandy field near the edge of the Sahara desert. The rare dunes, which are often confused with human-made pyramids, are likely several centuries old, recent research has revealed.

The unusual structures are located in Erg Chebbi. This field of open, windswept sand — or erg — covers around 65 square miles (170 square kilometers) in southwest Morocco along the northwestern edge of the Sahara. The erg is surrounded by flat lowlands but contains some of the tallest dunes in the Sahara, making it stand out like a mountain range when viewed from afar.

The town of Merzouga is also visible in the bottom right of the image. This settlement is built on top of a large aquifer, or underground reservoir, which allows palm groves to flourish alongside the desolate landscape and draws in tourists who are looking to explore the erg's sandy peaks.

A star dune is a type of sand dune that has at least three ridges coming from a central peak, which gives it a star-like shape when viewed from above, according to NASA's Earth Observatory. But when they're viewed from the side, their multiple smooth slopes, known as "slip faces," can make the star dunes look very similar to pyramids from ground level.

These dunes, which can grow to be over 300 feet (90 meters) tall, form only in locations where wind directions change constantly, which allows their different slopes to form, according to the National Park Service. As a result, they move by just a couple of inches every year in the direction of the strongest prevailing wind. That's a lot slower than some other wandering dunes, which can travel up to 1,000 feet (300 m) annually when blown in a single direction.

Related: See all the best images of Earth from space

The largest star dune in Erg Chebbi, Lala Lallia, is 330 feet (100 m) tall and is located slightly to the north (left) of the dunes in the satellite image. In March 2024, researchers revealed that this dune is around 900 years old, which is much younger than previous estimates had suggested.

The same study also revealed that some of the sand buried at the base of this dune is up to 13,000 years old. These grains predate an 8,000-year period of climatic change that occurred after the end of the last ice age. During this time, the Sahara was temporarily transformed into a swampy environment covered in vegetation — a shift that ended only around 4,000 years ago, researchers wrote at the time.

On Earth, star dunes are also found in China, Namibia, Algeria, Saudi Arabia and several U.S. states, including California and Colorado. But very similar structures can be found on Mars, according to NASA.

A spotted hyena has been reported in Egypt for the first time in thousands of years after it ventured far beyond its normal range. The hyena then ate two goats and was swiftly killed by humans in a pickup truck.

Spotted hyenas (Crocuta crocuta) live across much of sub-Saharan Africa, but the species went extinct in what is now Egypt 5,000 years ago, when a changing climate made the region too dry for their prey.

The wandering hyena was found last year deep in the Sahara desert, hundreds of miles north of the species' normal northern limit. Researchers aren't sure what the hyena was doing so far north, but it could have been following prey animals that were taking advantage of a wet spell in the region.

Local people tracked and killed the hyena in Wadi Yahmib, about 19 miles (30 kilometers) from the Sudanese and Egyptian border, after it killed two goats, according to the study, published Nov. 15, 2024 in the journal Mammalia.

"The local people are master trackers and familiar with all large mammals of the area," the study authors wrote. "The hyena was tracked by local people, located, chased, and intentionally hit by a pickup truck."

Livestock losses can be financially devastating for people in the region. The local people live alongside striped hyenas (Hyaena hyaena), but these smaller hyenas typically don't attack livestock, according to the study.

A researcher photographed and filmed the dead hyena and sent the images to colleagues for identification. Study lead author Abdullah Nagy, a wildlife ecologist at Al-Azhar University in Egypt, told Live Science he was surprised when he saw the photographs.

Related: Yellowstone's 'queen of the wolves' killed by rival pack after living to 11 years old and having 10 litters of pups

Nagy explained that Egypt underwent a significant environmental shift around 5,000 years ago when the Sahara began to get drier through a process called aridification.

"Previously, the region boasted a lush landscape similar to sub-Saharan Africa, supporting a diverse range of large mammals such as elephants, giraffes, leopards, and spotted hyenas," Nagy said. "However, a gradual aridification process transformed the ecosystem into the Sahara Desert, an environment no longer suitable for these species."

The study highlights that more recent environmental changes could have enabled at least one hyena to return to Egypt. A regional weather cycle over the last five years increased rainfall and plant growth in the region, which could have supported prey for a curious, traveling hyena, according to a statement released by Mammalia's publisher, De Gruyter, on Tuesday (Jan. 21).

The study authors noted that in addition to prey, slaughterhouses could have attracted hyenas to the area. The researchers also speculated that Sudan's political instability and civil war might have contributed to an increase in spotted hyenas in the region. That's because hyenas engage in anthropophagy — meaning they eat human flesh — and will prey on weakened or vulnerable humans, especially during times of human crisis, according to the study.

Was the hyena alone?

Spotted hyenas normally live in complex social groups that can include up to 100 individuals. A pack of hyenas working together can hunt big prey such as young rhinos, wildebeest and zebras, according to San Diego Zoo. However, hyenas are very versatile carnivores, capable of hunting alone and scavenging food from humans if necessary.

Nagy noted that the hyena killed in Egypt could have been hunting alone, but it may also have had company.

When prey isn't abundant, spotted hyenas hunt alone, but it's possible that others were there and not detected, he said.

A giant patch of black, fossilized lava that was spewed across the Sahara desert over millions of years looks like an eerie, gold-speckled shadow in this stunning composite of three years' worth of satellite photos.

The shadowy mass, known as the Haruj volcanic field, covers around 17,000 square miles (44,000 square kilometers) in central Libya and contains roughly 150 extinct volcanoes, ranging from small vents and chimneys to larger shield volcanoes, according to the U.S. Geological Survey.

Some of the volcanic rocks are up to 6 million years old, while others were left by eruptions that happened as recently as a few thousand years ago, according to the Global Volcanism Program at the Smithsonian's National Museum of Natural History.

While the dark color of the petrified lava makes the field look smooth and flat from above, the field is extremely uneven, with areas where multiple eruptions have caused layers of rock to pile up above their surroundings. The site is also littered with raised vents and at least 30 cones that stand more than 330 feet (100 meters) tall, according to the Global Volcanism Program.

The tallest peak in the field stands roughly 3,900 feet (1,200 m) above sea level.

Related: See all the best images of Earth from space

The satellite image above is what is known as a "best pixel mosaic" and was made using a computer program that sorts through multiple images of the same spot pixel by pixel to create a final image that is free from obscuring elements, such as clouds or dust storms, according to NASA's Earth Observatory.

This model also selected pixels where patches of sand that have settled in between gaps in the lava catch the sunlight, which has created the golden speckles littered across the field. These sandy spots are much less obvious in other satellite images of the area.

Volcanic history

Most volcanoes are born along fault lines that intersect Earth's tectonic plates, because this is where the planet's crust is weakest and magma from the mantle can easily rise to the surface.

However, the Haruj volcanic field is not located near any known fault lines. Instead, the lava there was likely dragged up directly from the mantle by a surge of hot, rocky material — known as a mantle plume — which created a reservoir of magma below the field.

As a result, lava from the Haruj volcanoes would have slowly bubbled up and oozed out from the field's multiple vents, similar to modern eruptions that occur at Hawaii's Kilauea volcano, rather than being ejected in explosive eruptions, according to the Earth Observatory.

Some researchers think Haruj is made up of two separate volcanic fields: Al Haruj al Aswad, which is located in the north and contains much older lava; and Al Haruj al Abyad, which is located in the south and was created more recently. However, it is hard to tell where one of these fields ends and the other begins, so it is more commonly thought of as a single entity.

This striking astronaut photo shows off an "eye-catching" impact crater in the Sahara Desert. The oculus-like structure is surrounded by migrating sand dunes that are capable of traveling more than 100 feet (30 meters) every year.

The Aorounga structure is a 7.8-mile-wide (12.6 kilometers) impact crater located in the southeast Sahara in northern Chad. The crater is made up of two rings that give the structure its eye-like appearance: An inner ring with a central hill, or uplift structure, that looks like a pupil; and an outer ring that looks like an eyelid. The rings rise around 330 feet (100 m) above the surrounding ground but have been heavily eroded over time — similar to other ancient impact craters — and were likely even taller and wider originally.

Experts believe that the structure formed around 345 million years ago and was likely created by a meteor around 2,000 feet (600 m) across, according to estimates from the Lunar and Planetary Institute. An impactor of this size, known as a "city-killer" asteroid, would have caused widespread damage across the north of Africa and may have even triggered climatic effects on a global scale.

The structure also has several dark lines running across both of its rings, which are sections of massive ridges, known as yardangs, according to the U.S. Geological Survey. These ridges, which can reach up to 100 feet (30 m) above ground level, stretch across the surrounding areas for dozens of miles, as you can see in the 2016 astronaut images below.

Related: See all the best images of Earth from space

A group of five barchan, or "horned," sand dunes can be seen in a zoomed-in version of the 2013 photo (see below). Over time, these arrowhead-shaped piles of sand are pushed across the desert by the wind and move in the opposite direction that their "horns" are pointed in, according to NASA's Earth Observatory.

By comparing their location in this image with satellite images of the same area in late 2003, researchers were able to work out exactly how far they had moved in just over nine years. From left to right, the five dunes — labeled 1, 2, 3, 4 and 5 — moved by 1,037 feet (316 m), 902 feet (275 m), 1,329 feet (405 m), 1,043 feet (318 m), and 1,250 feet (381 m) respectively.

The biggest migrators, 3 and 5, are also the smallest dunes, which is consistent with what we know about how these dunes move, according to the Earth Observatory. Dunes smaller than these can be ripped apart within a decade.

Barchan dunes have long been known to migrate across the Sahara. However, scientists are only just beginning to work out exactly how far they can travel by tracking their movements with satellite images. Researchers hope these advancements could be used to forecast the sand's movements, which could help mitigate problems caused by the dunes obstructing roads and smothering agricultural land, according to the Earth Observatory.

Radar images of the Aorounga structure taken from space in the late 1990s have also revealed that the eye-shaped rings could be part of a "crater chain." At least two other smaller craters were identified on either side of the structure, suggesting that smaller parts of the Aorounga meteor broke off from the falling asteroid and impacted the surrounding areas, according to The Planetary Society.

Scientists have found the first evidence of insects crossing an entire ocean — after finding butterflies that made a 2,600-mile (4,200 kilometers) journey across the Atlantic.

Gerard Talavera, an evolutionary biologist at the Botanical Institute of Barcelona, made the discovery in French Guiana in 2013, when he spotted a flock of painted lady butterflies (Vanessa cardui) sitting on the sand, their wings tattered and shot through with holes.

This discovery puzzled scientists, as the tiny species can be found around the world, but not in South America. Now, after a decade of investigation, the researchers have pieced together an answer for how the butterflies got there: They embarked on the first transoceanic flight recorded in an insect. 

The researchers published their findings Tuesday (June 25) in the journal Nature Communications.

"We tend to see butterflies as a symbol of the fragility of beauty, but science shows us that they can perform incredible feats," study co-author Roger Vila, a researcher at the Institute of Evolutionary Biology in Barcelona, said in a statement. "There is still much to discover about their capabilities."

Insect migrations aren't uncommon, but they're difficult to track. Scientists usually rely on records from amateur insect watchers and radar coverage to study insect movements, but these are limited and not always reliable.

Related: 'Russian doll' set of stomach-bursting parasites released inside butterfly on remote Finnish island

To work out how the painted lady butterflies got to French Guiana, the researchers pulled together multiple strands of evidence. They sequenced the butterflies' genomes, which revealed that they were closely related to populations in Europe and Africa. The team also analyzed pollen DNA on the insects' 2-inch-long (5 centimeters) bodies and identified two plant species only found in tropical Africa. In addition, they studied isotopes of hydrogen and strontium on the butterflies' wings, finding that they were unique to western Europe. 

Taken together, this evidence ruled out a North American origin for the insects and suggested that their lives began in Africa or Europe.

"The painted lady butterflies reached South America from West Africa, flying at least 4,200 km over the Atlantic. But their journey could have been even longer, starting in Europe and passing through three continents, implying a migration of 7,000 km [4,350 miles] or more," study co-author Clément Bataille, a professor of earth and environment science at the University of Ottawa in Canada, said in the statement. "This is an extraordinary feat for such a small insect." 

Painted lady butterflies are already known to migrate up to 9,000 miles (14,500 km) between Europe and Africa, including crossing the unforgiving expanse of the Sahara. 

But this trip is made with nightly stops to rest and refuel. To reach French Guiana from West Africa, the butterflies would have to fly for up to eight days without rest.

To resolve this part of the mystery, the scientists analyzed wind currents that rise from the Sahara and blow dust from Africa to the Americas. They found that by gliding upon these aerial highways, the butterflies could complete their remarkable journey.

"The butterflies could only have completed this flight using a strategy alternating between minimal effort to avoid falling into the sea, facilitated by ascending winds, and active flight, which requires more energy consumption," study co-author Eric Toro-Delgado, a doctoral student at the Institute of Evolutionary Biology, said in the statement. "We estimate that without wind, the butterflies could have flown a maximum of 780 km [485 miles] before exhausting all their fat and thus their energy."

The finding highlights insects' abilities to traverse huge distances in ways scientists previously haven't considered.

"This discovery opens new perspectives on the capabilities of insects to disperse over long distances, even across seas and oceans. It is possible that we are underestimating the frequency and impact of these movements on our ecosystems," study lead-author Talavera said in the statement. "Throughout history, migratory phenomena have been important in defining the distributions of species that we observe today."

This 2017 satellite photo shows the abstract beauty of one of the world's most terrifyingly hostile environments.

The Tanezrouft Basin is a large region of the Sahara mainly located in southern Algeria and northern Mali. The area receives less than 0.2 inches (5 millimeters) of rain a year on average, making it "hyperarid." Temperatures can reach over 122 degrees Fahrenheit (50 degrees Celsius) during summer, according to NASA's Earth Observatory.

The basin is almost completely devoid of life apart from some Tuareg nomads who occasionally make the treacherous journey through the region on a caravan route that dates back more than 1,500 years. But this can be a deadly trip due to the region's lack of visible landmarks, which can cause even the most experienced travelers to get lost. As a result, the basin is colloquially known as the "Land of Terror."

Thousands of years of sandstorms have eroded sediment and sand from parts of the basin, which has revealed ancient concentric folds in the region's undulating sandstone bedrock that date to the Paleozoic era (541 million to 252 million years ago). Flashes of green are pitted around these folded rocks, which are salt flats often located in steep canyons.

When viewed from space, "the exposed geologic features create an arresting work of abstract art," NASA representatives wrote.

Related: 12 amazing images of Earth from space 

The dramatic landscape also reveals that Tanezrouft Basin hasn't always been so hostile to life.

Some of the salt flats in this real-color image lay in canyons up to 1,600 feet (490 meters) deep. The scale of these steep gullies and the shape of their smoothed sides are signs that they were carved out by flowing water, potentially from intermittent flooding over millions of years, P. Kyle House, a researcher with the U.S. Geological Survey, told NASA's Earth Observatory. 

This suggests the region could have once been a more luscious environment potentially capable of supporting a diverse ecosystem.

Today, the salt flats and their canyons either lie within or intersect with the exposed sandstone folds, creating the shapes seen in this image. "These patterns are striking and reminiscent of landscapes formed on folded strata in, for example, the Red Desert of southern Wyoming and even parts of the heavily forested Appalachian Mountains of the Eastern United States," House said.

The "Eye of the Sahara" — also known as the "Eye of Africa" or the Richat structure — is a giant rock dome, carved with concentric rings, that looks like a giant bullseye when seen from above. The eye is visible from space and has been known to astronauts and scientists since the earliest crewed missions in the 1950s, according to the European Space Agency (ESA).

Estimates of the Eye of the Sahara's dimensions range from 25 to 31 miles (40 to 50 kilometers) in diameter. The eye forms a near-perfect circle in the desert of Mauritania, which initially led scientists to think it was an impact structure from a meteor. However, subsequent research found the dome was shaped by tectonic uplift during the Cretaceous period (between 145 and 66 million years ago) and laid bare through erosion.

The Eye of the Sahara stands out like an oversized ammonite among an immense sea of sand known as the Erg Oudane, which stretches roughly 350 miles (560 km) east to Mali. Ergs are areas of desert that span at least 48 square miles (125 square kilometers) and feature wind-swept sands with little to no vegetation. The eye towers about 660 feet (200 meters) above the surrounding sands, which rise against its southern edge and occasionally obscure parts of the structure in photographs, according to ESA.  

Related: Mystery of enormous Saharan 'star dune' finally solved — and it wasn't what scientists were expecting

The center of the Eye of the Sahara is a round plateau of limestone and breccias — sedimentary rocks with large, broken fragments that are cemented together by a fine-grained matrix — according to a 2021 study. The rest of the eye slopes down from this plateau in a circular pattern of ridges and grooves that have been sculpted by wind and water over the eons. The ridges are mostly made of resistant quartzite, while the grooves consist of less-resistant sedimentary rocks that wear away more quickly. 

The reason why the eye is so round remains unclear, according to the Lunar and Planetary Institute. Erosion has exposed four types of igneous rock — gabbros, rhyolites, carbonatites and kimberlites — which are younger than the center of the eye, indicating that jets of molten rock rose and solidified at the surface. Several faults are also visible on the outer rings of the eye, suggesting that layers of rock shifted apart in the process. 

The Eye of the Sahara is a geological marvel, but it also holds archaeological significance, according to Geographical, a magazine published by the U.K.'s Royal Geographical Society. Excavations have unveiled 2-million-year-old Acheulean and pre-Acheulean tools that are associated with two species of ancient human ancestors: Homo erectus and Homo heidelbergensis. 

Proponents of the debunked myth of Atlantis — a "lost" island subcontinent idealized by some as an advanced, utopian society — claim the Eye of the Sahara is evidence of the city described by Plato in his "Timaeus" and "Critias" dialogues.

But "together, modern archaeology and geology provide an unambiguous verdict," Ken Feder, a professor emeritus of archaeology at Central Connecticut State University, previously told Live Science. "There was no great civilization called Atlantis."

There's no need to turn to mythology for answers when geology provides enough of its own.

Discover more incredible places, where we highlight the fantastic history and science behind some of the most dramatic landscapes on Earth.

Incredible, first-of-its-kind footage reveals a tiny swallow's battle for survival inside a mammoth sandstorm as it migrates across the Sahara Desert. The bird, which weighed less than an ounce (28 grams),  was recorded while undertaking the most difficult part of its epic journey north for the summer. 

Every year, European barn swallows (Hirundo rustica rustica) migrate 6,000 miles (9,700 kilometers) from northern Europe to southern Africa, and then back again. The new clip, captured for  National Geographic's "Incredible Animal Journeys," shows a solitary barn swallow on the perilous stage across the desert. 

"Swallows are amongst nature's 'Top Guns' — fast and acrobatic, able to turn on a dime with a flick of their long tail feathers — so finding a bird the size of your hand in a desert almost the size of the U.S. was always going to be a challenge," Sarah Gibbs, executive producer on the series, which premiered Nov. 19, told Live Science in an email. "Filming that bird in a sandstorm, on a long lens, buffeted by high winds, took it to the next level."

The production team spotted the swallow in Morocco on the northern edge of the Sahara. This is the point where the swallows are finishing their journey across the desert, having spent days in searing-hot temperatures with no water. A scientist who studies the migration each year, along with an avid birder and long-lens camera operator assisted the team.

Related: Upcoming solar maximum could scramble migrating birds' internal compass, new study shows

"The storm was an unexpected bonus — but it made filming even tougher," Gibbs said. 

Barn swallows weigh between 0.6 and 0.7 ounce (17 to 20 grams) and are around 6 inches (15 centimeters) long. As the sandstorm hit, winds picked up to around 40 mph (64 km/h). The production team "focused in on a swallow really struggling," she said. "A master of flight at the mercy of the elements, tossed around like a boat at sea. It was a blink and you'll miss it moment as the bird sought refuge in a bush, waiting for the storm to pass."

European barn swallows migrate north in the spring to mate and rear chicks, then head south as temperatures begin to fall ahead of winter. The migration is perilous, with high mortality rates recorded each year. The Sahara is one of the deadliest points of the trip. "It takes five days to cross and a swallow can only go a few days without drinking," Gibbs said. 

After making it through the desert, the barn swallow was filmed reaching a water source and drinking for the first time in days. From there, the bird still had to fly another 2,000 miles (3,200 km) to reunite with its mate — before starting the cycle again. 

Millions of years ago, the Sahara was a green oasis covered in trees and grassland. So how did it become world's biggest hot desert, roughly the size of the entire U.S.? 

In his book "When the Sahara Was Green," (Princeton University Press, 2021) Martin Williams explores the little-known history of this iconic landscape. In the extract from the book below, the author looks at how a vanishing ocean and global cooling set the stage for the birth of the Sahara desert. 

During most (but not all) of the Paleocene and Eocene, about 66 to 34 million years ago, much of what is now the southern and central Sahara enjoyed a hot, wet climate and was covered in equatorial rain forest. Chemical weathering was intense beneath the highly organic and densely vegetated soil surface, and rocks exposed near the surface were weathered to depths up to fifty meters, a process known as deep weathering.

During the ensuing Miocene (23 to 5.3 million years ago), this region experienced uplift as well as climatic desiccation. The climatic desiccation already under way was enhanced by two independent factors.

One was the late Miocene shrinking of the vast Tethys Sea as Africa moved north towards Eurasia. The Mediterranean Sea is the shrunken remnant of this once extensive sea. As a consequence, northern Africa was deprived of an abundant supply of moist air blowing from the Tethys Sea. The second critical factor was late Miocene global cooling about 8 to 6 million years ago, which saw the spread of the modern terrestrial plant and animal ecosystems so familiar to us today.

Differential Miocene uplift across the Sahara combined with climatic desiccation and a reduced protective plant cover ushered in a period of intense erosion of the deep weathering mantle and exposure of the irregular weathering front. In many parts of the Sahara today the geomorphic legacy of this process consists of large boulders perched somewhat precariously on the rocks beneath. Uplift of the Saharan uplands caused a wave of fluvial erosion. Rivers flowing from the uplands deposited gravels, sands, and clays during the final phase of widespread fluvial erosion across the Sahara.

Related: Could the Sahara ever be green again?

The origin of the Sahara as a desert probably stems from about this time. However, the Sahara was not as universally arid during the Miocene as it is today. There were quite long intervals of wetter climate during which Mediterranean plants migrated slowly southwards into the central and southern Sahara, while plants from the wet tropics moved slowly northwards. 

Today the only evidence of these great migrations consists of some sparse relict populations of both Mediterranean and tropical plants that now occupy mountain refugia in the Hoggar, Tibesti, Aïr, and Jebel Marra. Plant migration at these times was facilitated by the presence of former waterways and probably took place along their valleys. Some very big rivers flowed northwards from what is now the Chad Basin across the Sahara to the Mediterranean. 

These rivers carved very wide valleys, some of which are clearly visible today on the ground in the southern Libyan Desert between Tibesti volcano and the three large sandstone plateaux located just to the east of the northern tip of Tibesti. They are even more spectacular when seen from space. The combined evidence from plant and animal fossils and sediment geochemistry also confirms that the climate in the headwaters of these Miocene rivers was relatively humid, with the late Miocene vegetation in the Chad Basin comprised of a mosaic of wetlands, savanna grasslands, and woodlands. 

But a very strange surprise was in store for the Mediterranean coastal regions of North Africa.

A very remarkable series of events took place during the late Miocene between 5.96 and 5.33 million years ago. At intervals during that time the Mediterranean was cut off from the Atlantic, dried out within a few centuries each time, and became a salt desert. Some geologists have suggested that the repetitive drying out of the Mediterranean was caused by earth movements. I do not find this suggestion convincing. I think it is far more likely that we are dealing with global fluctuations in sea level linked to the growth and decay of ice caps in West Antarctica.

During glacial intervals, as the ice caps grew, global sea level fell, until the shallow sill at the western end of the Mediterranean located beneath the present Straits of Gibraltar emerged above sea level and acted as a very effective dam, preventing the free flow of Atlantic surface water into the Mediterranean Basin and outflow at depth from the Mediterranean. The sill now has an average depth of about 1,200 feet (365 meters), and at the point where Africa is closest to Europe, it is about 656 feet (300 m) deep. It must have been quite shallow in the late Miocene and would have become deeper since then as a result of marine erosion.

In step with the glacial intervals, phases of inflow when ice volume was low and sea level was high alternated with phases of desiccation. The end result was accumulation of a layer of salt and other evaporites up to about 0.6 miles (1 kilometer) thick on the floor of the Mediterranean.

Whatever the cause, desiccation of the Mediterranean would have deprived northern Africa of a major source of moisture. These salt deposits are now buried beneath a protective layer of marine Pliocene sediments. A similar salt desert formed at this time on the floor of the Red Sea so that Africa was probably isolated genetically from Eurasia for much of that time, perhaps facilitating the emergence of our hominin ancestors in Africa and nowhere else.

Another consequence of the repeated drying out of the Mediterranean was repeated lowering of the outlets of all rivers draining into the Mediterranean, leading to the formation of some very deep river canyons. The Nile, for example, cut down 1.5 miles (2.5 km) north of Cairo and flowed at 557 feet (170 m) below present sea level at Aswan, located 745 miles (1,200 km) upstream of the present Nile delta. During that time, the Nile eroded about 19,200 cubic miles (80,000 cubic km) of rock from its canyon and deposited it on the floor of the eastern Mediterranean.

The net effect … was the gradual emergence of the vast and arid land that we today refer to as the Sahara. The stage was now set for the birth and growth of desert dunes and the great sand seas that now cover about one-fifth of the Sahara.

Text from WHEN THE SAHARA WAS GREEN by Martin Williams. Copyright © 2021 by Princeton University Press. Reprinted by permission of Princeton University Press.

The paperback version of the book is set for release on November 7. 

Researchers have proposed that an unusual rock, which was recently discovered in northern Africa, could be the first ever known "boomerang meteorite" — a space rock that originated on our planet before being ejected into space and then later tumbling back to Earth. However, not everyone agrees with the new findings, which have yet to be peer-reviewed.

The meteorite, which is named NWA 13188 and weighs around 23 ounces (646 grams), was discovered by meteorite hunetrs in an unknown part of the Sahara Desert in Morocco in 2018. Nobody saw the rock fall to Earth and its composition was discovered to be very similar to a specific type of volcanic rocks known to scientists, which has led to speculation about its origins. 

But a group of researchers who have recently analyzed the rock now believe that it is a terrestrial meteorite, a rock that originated on Earth and was catapulted into space millions of years ago, and which has only just fallen back to our planet. Jérôme Gattacceca, a meteoriticist at Aix-Marseille University in France, presented his team's findings July 11 at an international geochemistry conference in Lyon, France. (Their work has not yet been published in a peer-reviewed journal.)

If the team is correct, NWA 13188 will be recognized as the first official terrestrial meteorite found on Earth. 

Related: Never-before-seen crystals found in perfectly preserved meteorite dust

The researchers believe that NWA 13188 is a meteorite because it has a "well-developed fusion crust" — a fine layer of heat-shocked rock on its surface, which is a sign that it partially burned up in Earth's atmosphere and is not a feature found in volcanic rocks on Earth. 

The team also found traces of isotopes (elements with differing numbers of neutrons in their nuclei) including beryllium-3, helium-10 and neon-21, which suggest that the rock was exposed to cosmic rays — high-energy particles that move through space at nearly the speed of light. The level of these isotopes suggests that the rock was in space for at least 10,000 years, but possibly much longer.

There are two possible scenarios for how the meteorite was once ejected into space: The first is that a massive volcanic eruption launched it directly into space, and the second is that it was catapulted out of the atmosphere by a colossal asteroid impact. The researchers believe that the latter explanation is the most likely because no recorded volcanic eruption has been powerful enough to launch rocks into space.

Not everyone is ready to classify the rock as a boomerang meteorite.

"It is an interesting rock," Ludovic Ferrière, a curator of the meteorite collection at the Natural History Museum Vienna in Austria, who was not involved with the new analysis, told Live Science's sister site Space.com. But it requires "more investigations to be conducted before making extraordinary claims." Without being able to trace it to an impact crater or knowing how old it is, it is hard to pin down exactly how the rock left or reentered Earth, he added.

Others think that the rock could also have been birthed elsewhere in the solar system despite its similarities to Earth rocks. "I think there is no doubt that this is a meteorite," Frank Brenker, a geologist at the Goethe University Frankfurt in Germany, who was not involved with the new analysis, told Space.com. "It is just a matter of debate if it is really from Earth."

The research team is planning further analysis to work out the exact age of the rock and search for any other clues that may determine how it was catapulted away from Earth.

NWA 13188 could potentially be the first boomerang meteorite found on Earth, but it is not the first possible terrestrial meteor to ever be discovered. In a 2019 study published in the journal Earth and Planetary Science Letters, researchers identified an unusual chunk of rock from the moon during the Apollo 14 mission in 1971, which contains tiny fragments of quartz, feldspar and zircon that all likely originated on Earth. They propose that this chunk of rock was ejected from our planet when the moon was much closer to our planet, billions of years ago.

One of the world’s most dangerous prehistoric ecosystems just added another huge predator to its lineup. In the Bahariya Formation, a famous fossil site in Egypt’s Sahara Desert, a team of Egyptian and American paleontologists recently uncovered a huge fossil vertebra belonging to a newly described species of meat-eating abelisaurid dinosaur — a bipedal, carnivorous group that lived during the Cretaceous period (145 million to 66 million years ago). 

Like other abelisaurids, the newfound dinosaur had a shortened, bulldog-like face. And despite its ferocious appearance, this carnivore probably wasn’t the biggest, baddest boss to roam its stomping grounds.

"We’re about 99% sure that, unlike some of its relatives from other times and places, this particular abelisaurid was not at the top of its food chain," Matthew Lamanna, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh and one of the researchers who discovered the dinosaur, told Live Science in an email.

Related: Crocodile-faced dinosaur may have been Europe's largest ever predator

Though Lamanna and his fellow scientists found only a single bone, they were able to identify the fossil as an abelisaurid vertebra almost immediately, based on distinctive structures called epipophyses. "That’s a multisyllabic word that basically means 'sticky-outy bits on the top left and top right of the vertebra,'" Lamanna said. This abelisaurid is the first dinosaur of its kind to be discovered at the Bahariya Formation site. After running a computer-based analysis of the bone’s morphology, the team concluded that it belonged to a previously unknown species, which has yet to be given a scientific name. They published their findings June 8 in the journal Royal Society Open Science. 

An abelisaurid somewhat resembled a heavy-set Tyrannosaurus rex, only with even stubbier arms, Smithsonian Magazine reported. They roamed the Southern Hemisphere from the middle of the Jurassic period, about 170 million years ago, right up until the Chicxulub asteroid brought the Cretaceous to a screeching halt. Perhaps the most famous abelisaurid is the horned Carnotaurus, a Patagonian predator that reached 25 feet (7.6 meters) long, according to London's Natural History Museum. Its name is taken from the Latin words for "flesh" and "bull," and animated versions of this fearsome carnivore have appeared in Apple TV's "Prehistoric Planet" and in the "Jurassic Park" franchise (though, its portrayals display varying degrees of scientific accuracy). 

The researchers suspect that the newly discovered abelisaurid was smaller than Carnotaurus, likely reaching just 16 to 20 feet (5 to 6 meters) in length. And compared to the predators who shared its native habitat 98 million years ago, the newfound abelisaurid would have been a relative pipsqueak.

The Bahariya Formation was previously home to a uniquely predator-rich slice of prehistoric life. This once-vast mangrove swamp hosted numerous species of fish, turtles, snakes and dinosaurs. The newfound abelisaurid would have rubbed elbows (metaphorically speaking) with a T. rex lookalike known as Carcharodontosaurus; a mysterious giant therapod (bipedal, three-toed dinosaurs) called Bahariasaurus; the monstrous Spinosaurus, which had long and slender crocodilelike jaws and a sail growing from its back; and giant predatory fish and crocodilians.

Finding so many large predators living together in a single ecosystem is rare,  Lamanna said. "How this 98-million-year-old environment managed to support not one but four massive predatory dinosaurs remains a puzzle," he added.

The newly described fossil is now stored in the permanent collection of Mansoura University's Vertebrate Paleontology Center in Egypt. In the future, Lamanna and his coauthors plan to return to the Bahariya Formation and search for more bones from their abelisaurid — and maybe even give it a name.

"Hopefully more of this Bahariya beast will turn up sooner or later," Lamanna said. 

Originally published on Live Science.

A strange extraterrestrial space rock unearthed in the Sahara Desert could be the first evidence on Earth for a rare type of supernova.

The chemical composition of the Hypatia stone, which was first discovered in Egypt in 1996, suggests it may contain dust and gas that once surrounded an enormous type of supernova, the spectacular explosion of a dying star.

Type Ia supernovas typically take place inside dust clouds where a white dwarf, or the shriveled husk of a collapsed star, shares an orbit with a larger, younger star that still has some fuel to burn. The smaller and denser white dwarf uses its immense gravitational pull to snatch some of the younger star’s fuel, which it gorges on relentlessly, stretching the younger star into a teardrop shape. The act of cosmic canniblism eventually ends in mutual destruction, however, as the vampiric white dwarf grows large enough for nuclear reactions to reignite in its core. After a sudden bright flash, an enormous supernova blast hurls the irradiated contents of both stars outwards to mingle and merge with the dust.

Related: 11 fascinating facts about our Milky Way galaxy 

In the case of the Hypatia stone, the cocktail of dust and gas likely drifted through space over billions of years until it arrived in our cosmic backyard, eventually solidifying into the larger parent body of the Hypatia stone sometime during the birth of our solar system, the new research suggests. Once formed, likely somewhere in the outer solar system, the rock eventually hurtled to Earth, shattering into fragments as it landed.

"In a sense, we could say, we have caught a supernova Ia explosion in the act, because the gas atoms from the explosion were caught in the surrounding dust cloud, which eventually formed Hypatia's parent body," study lead author Jan Kramers, a geochemist at the University of Johannesburg in South Africa, said in a statement.

To figure out where the rock came from, the researchers performed a chemical analysis of a tiny sample of the Hypatia stone using non-destructive techniques. These revealed that the rock had unusually low amounts of silicon, chromium and manganese — elements that are rare in the inner solar system — while also having abnormally high levels of iron, sulfur, phosphorus, copper, and vanadium for objects in our cosmic neighborhood. 

"We found a consistent pattern of trace element abundances that is completely different from anything in the solar system, primitive or evolved. Objects in the asteroid belt and meteors don’t match this either," Kramers said.

Further tests, which compared the rock’s element concentrations with those we’d expect to see in our region of space, came back with even more surprising results — the stone wasn’t even from our arm of the galaxy, and it had too much iron, too little silicon, and too low a concentration of elements heavier than iron to have come from a solo red dwarf explosion (a type II supernova).

An exhaustive search of star data and modeling left the team with no other likely explanation for the rock’s origin than a type Ia supernova, which would explain the stone's unusual element concentrations. The ratios of eight of the 15 elements analyzed by the researchers (silicon, sulfhur, calcium, titanium, vanadium, chromium, manganese and nickel) fit very closely to the concentrations predicted for a white dwarf explosion.  

"If this hypothesis is correct, the Hypatia stone would be the first tangible evidence on Earth of a supernova type Ia explosion," Kramers said. "Perhaps equally important, it shows that an individual anomalous parcel of dust from outer space could actually be incorporated in the solar nebula that our Solar System was formed from, without being fully mixed in."

But doubts still remain. Six of the stone’s elements — aluminum, phosphorus, chlorine, potassium, copper, and zinc — are present at concentrations that ranged from 10 to 100 times what would be expected for a type Ia supernova. The researchers think this could point to the supernova’s origins as a red giant star that preserved more of its original elemental composition than the models predicted.

"Since a white dwarf star is formed from a dying red giant, Hypatia could have inherited these element proportions for the six elements from a red giant star. This phenomenon has been observed in white dwarf stars in other research," Kramers said.

The scientists published their findings on the weird alien rock in a forthcoming issue of the journal Icarus.

Originally published on Live Science.

The Sahara is the largest hot desert in the world and the third-largest desert overall, behind the cold deserts of Antarctica and the Arctic. The Sahara is one of the harshest environments on Earth, covering 3.6 million square miles (9.4 million square kilometers), an area about the size of the United States (including Alaska and Hawaii) and spanning nearly a third of the African continent. The name of the desert comes from the Arabic word ṣaḥrāʾ, which means "desert," according to the Encyclopedia Britannica.

What's the geography of the Sahara?

The Sahara is bordered by the Atlantic Ocean to the west, the Red Sea to the east, the Mediterranean Sea to the north and the Sahel savanna to the south. The enormous desert spans 10 countries (Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Sudan and Tunisia) as well as the territory of Western Sahara, a former Spanish colony that was annexed by Morocco in 1975, though control of the region is disputed by the Indigenous Saharawi people, the BBC reported in 2021.

The Sahara desert has a variety of land features, but it is most famous for the sand dune fields that are often depicted in movies. The dunes can reach almost 600 feet (183 meters) high, and they cover about 25% of the entire desert, according to the Encyclopedia Britannica. Other topographical features include mountains, plateaus, sand- and gravel-covered plains, salt flats, basins and depressions. Emi Koussi, an extinct volcano in Chad, is the highest point in the Sahara, reaching 11,204 feet (3,415 m) above sea level,  and the Qattara Depression in northwestern Egypt is the Sahara's deepest point, at 436 feet (133 m) below sea level.

Although water is scarce across the entire region, the Sahara contains two permanent rivers (the Nile and the Niger), as well as at least 20 seasonal lakes and huge aquifers, which are the primary sources of water for more than 90 major oases in the desert. Water management authorities once thought that the aquifers in the Sahara were "fossil aquifers" — water reserves that accumulated under different climate and geological conditions in the distant past — and feared that these resources would soon dry up due to overuse. However, a study published in the journal Geophysical Research Letters in 2013 discovered that the aquifers were still being fed via rain and runoff.

What kinds of plants and animals live here?

Despite the harsh, arid conditions of the Sahara, many plant and animal species call the region home. Approximately 500 plant species, 70 mammalian species, 90 avian species, 100 reptilian species and numerous species of spiders, scorpions and other small arthropods live in the Sahara, according to the World Wildlife Fund.

The camel is one of the most iconic animals of the Sahara, though its ancestors originated in North America. The ancestors of modern camels first appeared about 45 million years ago, and the large mammals eventually made their way to the African continent by traveling across the Bering isthmus between 3 million and 5 million years ago, according to a study published in 2015 in the Research Journal of Agriculture and Environmental Management. Camels were domesticated about 3,000 years ago on the southeast Arabian Peninsula, to be used for transportation in the desert, according to the University of Veterinary Medicine Vienna.

Camels, also known as the "ships of the desert," are well adapted to the Sahara's hot, arid environment, according to the San Diego Zoo. The humps on a camel's back store fat, which can be used for energy and hydration in between meals. Camels store energy so efficiently that they can go more than a week without water and several months without food.

Other mammal residents of the Sahara include gazelles, addaxes (a type of antelope), cheetahs, caracals, desert foxes and wild dogs. Many reptiles also thrive in the desert environment, including several species of snakes, lizards and even crocodiles in places where there is enough water. Several arthropod species also call the Sahara home, such as dung beetles, scarab beetles, "deathstalker" scorpions and many types of ants, according to the Sahara Conservation Fund.

Plant species in the Sahara have adapted to the arid conditions, with roots that reach deep underground to find buried water sources and leaves that are shaped into spines that minimize moisture loss, according to the BBC. The most arid parts of the desert are completely devoid of plant life, but oasis areas, such as the Nile Valley, support a large variety of plants, including olive trees, date palms and various shrubs and grasses.

What's the climate like in the Sahara?

Today, the Sahara has a dry, inhospitable desert climate. However, it alternates between harsh desert and another extreme — a lush, green oasis — every 20,000 years, according to a study published in 2019 in the journal Science Advances. The study's authors examined marine sediments containing dust deposits from the Sahara from the past 240,000 years. They found that the cycle between a dry and a green Sahara corresponded to the slight changes in the tilt of Earth's axis, which also drives monsoon activity. When Earth's axis tilted the Northern Hemisphere just a single degree closer to the sun (about 24.5 degrees instead of today's 23.5 degrees), it received more sunlight, which increased the monsoon rains and, therefore, supported a lush, green landscape in the Sahara.

Archaeologists have discovered prehistoric cave and rock paintings and other archaeological remains that shed light on what life was like in the once-green Sahara. Bits of pottery suggest that about 7,000 years ago, herders raised livestock and harvested plants in what now is an arid desert.

But for the past 2,000 years or so, the climate of the Sahara has been fairly stable — and dry. The northeastern winds strip moisture from the air over the desert and drive hot winds toward the equator. These winds can reach exceptional speeds and cause severe dust storms that can drop local visibility to zero. Dust from the Sahara travels on trade winds all the way to the opposite side of the globe.

Precipitation in the Sahara ranges from zero to about 3 inches (7.6 centimeters) of rain per year, researchers reported in 2014 in the journal American Meteorological Society. Occasionally, snow falls at higher elevations. Year-round, temperatures in dry, arid deserts such as the Sahara are about 60 to 77 degrees Fahrenheit (20 to 25 degrees Celsius) on average, soaring as high as 120 F (49 C) in the summer during the daytime and plummeting to 0 F (minus 18 C) during the winter at night, according to the University of California Museum of Paleontology Berkeley (UCMP).

Is climate change affecting the Sahara?

The area of the Sahara desert has grown nearly 10% since 1920, according to a 2018 study published in the Journal of Climate, and the desert will likely continue to expand at a comparable rate until 2050, according to another study, published in 2020 in the journal Scientific Reports. Although all deserts, including the Sahara, increase in area during the dry season and decrease during the wet season, human-caused climate change, in conjunction with natural climate cycles, is causing the Sahara desert to grow more and shrink less over time. The 2018 study's authors estimated that approximately a third of the desert's expansion was due to human-driven climate change.

One proposal for mitigating the effects of climate change is to install large-scale wind and solar farms in the Sahara. The farms would provide clean energy and reduce the amount of greenhouse gases entering the atmosphere, and may also promote increased precipitation in the vicinity, according to a 2018 study published in the journal Science. Simulations showed that precipitation over wind farms would double, on average, thereby increasing vegetation by an estimated 20%. The solar farm simulations produced similar results.

Additional resources

Discover what the Sahara was like millions of years ago, during the Cretaceous period, in this 2019 study in the journal Bulletin of the American Museum of Natural History. Find out more about one of the desert's most striking landscape features today, the Aïr Mountains in central Niger, in a case study from the U.S. Geological Survey. Visit the Sahara with Sir David Attenborough, to learn about the extreme adaptations that enable animals to survive the desert's harsh conditions, in an episode of the BBC One documentary, "Africa." 

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Li, Yan, et al. “Climate Model Shows Large-Scale Wind and Solar Farms in the Sahara Increase Rain and Vegetation.” Science, vol. 361, no. 6406, 2018, pp. 1019–1022., https://doi.org/10.1126/science.aar5629.

O'leary, Maureen A., et al. “Stratigraphy and Paleobiology of the Upper Cretaceous-Lower Paleogene Sediments from the Trans-Saharan Seaway in Mali.” BioOne Complete, American Museum of Natural History, https://bioone.org/journals/bulletin-of-the-american-museum-of-natural-history/volume-2019/issue-436/0003-0090.436.1.1/Stratigraphy-and-Paleobiology-of-the-Upper-Cretaceous-Lower-Paleogene-Sediments/10.1206/0003-0090.436.1.1.short.

“West Africa: Land Use and Land Cover Dynamics.” Landscapes of the Sahara Desert | West Africa, https://eros.usgs.gov/westafrica/case-study/landscapes-sahara-desert.

“Africa, Sahara.” BBC One, BBC, 31 Aug. 2019, https://www.bbc.co.uk/programmes/b01qh31v.

This article was updated on Feb. 24, 2022, by Live Science Senior Writer Mindy Weisberger.

On Tuesday (Jan. 19), one of the world's driest places awoke to an otherworldly dusting of frost.

In the Sahara Desert of northwestern Algeria, just outside the town of Ain Sefra, sand dunes were streaked with ice crystals as far as the eye could see. Local photographer Karim Bouchetata captured the unusual weather in pictures and videos that have since made headlines around the world.

Ain Sefra sits about 3,280 feet (1,000 meters) above sea level and is surrounded by the Atlas Mountains, near the Algerian-Moroccan border. While summer temperatures in the region regularly soar above 100 degrees Fahrenheit (38 degrees Celsius), January days average a much milder 57 F (14 C), according to Sky News. Tuesday's ethereal display of frost followed a rare night of 27-F (minus 3 C) temperatures.

Snow and ice accumulation in the northern Sahara is unusual, but not unprecedented. Tuesday's dusting marks the fourth time in 42 years that Ain Sefra has seen snow, with previous occurrences in 1979, 2016 and 2018. Those past snowfalls were much heavier than this week's display; in 2018, some areas of northwestern Algeria saw up to 15 inches (40 centimeters) of snow, while the 2016 blizzard dumped more than 3 feet (1 m) in select regions, Live Science previously reported.

The Sahara is the largest hot desert in the world, stretching more than 3.3 million square miles (8.6 million square kilometers) across northern Africa between the Atlantic Ocean and the Red Sea. (Antarctica and the Arctic, which each cover more area than the Sahara, are both considered cold deserts).

The Sahara is much more likely to see snowfall at higher altitudes, such as in the Atlas Mountains, NASA said in a statement following the 2018 snow dump, which was visible from space. The Moroccan side of the Atlas Mountains also saw substantial snowfalls in 2005 and 2012, according to NASA.

Originally published on Live Science.

Each year, dust from the Sahara Desert blows off Africa and across the Atlantic, but most years that plume isn't so massive it's nicknamed "Godzilla."

This June, the annual plume earned that nickname, as well as the title of the dustiest such event in the 20 years that scientists have kept records of these storms. All told, it contained between 60% and 70% more dust than a typical one of these plumes. It also traveled farther than the annual phenomenon, called the Saharan Air Layer, typically does.

The plume forms when thunderstorms and heavy winds pull dust up off the Sahara Desert beginning in late spring. The atmosphere then carries the dust away throughout the summer and into the early fall; how far the plume travels depends on local qualities of the atmosphere.

Related: The top 10 views of Earth from space

This year, the atmosphere carried the plume about 5,000 miles (8,000 kilometers), according to a statement from the European Space Agency (ESA), all the way out to the Caribbean islands and the southeastern United States.

ESA watched this year's dust plume throughout the month of July using its Copernicus Sentinel-5P satellite, a crucial component of its Earth-observation fleet. The satellite is tailored to study small particles in the air, like dust and pollutants.

Typically, much of the dust in the plume ends up sinking in the Atlantic Ocean, where it feeds tiny microscopic organisms called plankton. When it reaches land, the influx of dust can change the way ecosystems function, including by fertilizing the Amazon rainforest. It can also interfere with the formation of tropical storms and hurricanes, although it can be dangerous for humans to breathe in.

Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

A huge plume of Sahara Desert dust that drifted across the Atlantic Ocean has reached the southeastern United States.

These events have happened before, according to Marshall Shepherd, director of the University of Georgia's Atmospheric Sciences Program. Hundreds of millions of tons of dust from the giant North African desert collect in plumes and move west every year, and those plumes have long helped build up Caribbean beaches and fertilize soil in the Amazon, Shepherd wrote for Forbes. The dust also routinely poses respiratory issues for people in impacted areas. 

But this plume, which the National Weather Service (NWS) expects to blanket the U.S. Southeast and Puerto Rico through the weekend, is the biggest in at least the past 50 years.

The dust outbreak is "by far the most extreme of the MODIS satellite record — our most detailed, continuous record of global dust back to 2002," tweeted Michael Lowry, an atmospheric scientist at the Federal Emergency Management Agency (FEMA). MODIS (the Moderate Resolution Imaging Spectroradiometer) is a NOAA satellite instrument that takes daily pictures of the Earth to track weather events. 

Related: Fishy rain to fire whirlwinds: The world's weirdest weather 

The plume is 3,500 miles (5,600 kilometers) long, according to Reuters, and will impact regions as far flung as Puerto Rico, Texas and North Carolina over the weekend, according to the NWS. The Weather Channel reported that some of the dust might reach thelower Midwest and as far north as the Chesapeake Bay before receding back to the Atlantic on Monday (June 29). The National Oceanic and Atmospheric Administration (NOAA) said the dust plume extends vertically 5,000 to 20,000 feet (1,500 to 6,000 meters) into the atmosphere, which is just about as tall as Denali (20,310 feet or 6,190 m) in Alaska, the tallest mountain in North America.

One impact of the dust is that it will prevent rainstorms from forming, according to the NWS. The dense, dry air of the plume can stop or slow the formation of hurricanes and tropical storms, and the dust itself can trigger toxic algae blooms, according to NOAA. 

The brown haze should produce brilliant sunsets, according to The Weather Channel, but its most immediate impact will be reduced air quality, which can hurt anyone but is of particular concern to anyone with a chronic respiratory illness such as asthma. 

• Images: Amazing shots of storms light up weather photo contest
• 2 stunning photos catch monster thunderstorm's approach 
• Photo: Massive ice balls along Lake Michigan 

Originally published on Live Science. 

A "Godzilla dust cloud" from the Sahara Desert that's heading toward the United States this week is the largest and most concentrated dust cloud of its kind in the past 50 years, according to news sources.

As of June 22, the dust cloud — which some experts have dubbed the "Godzilla dust cloud" — had reached the Caribbean, spiking air quality to "hazardous" levels, according to the AP. People along the Gulf Coast may be next to experience the dusty visitor. 

Trade winds regularly carry dust clouds from the Sahara on a 5,000-mile (8,000 kilometers) journey across the Atlantic Ocean, but this particular formation "is an abnormally large dust cloud," Dan Kottlowski, AccuWeather senior meteorologist and lead hurricane forecaster, told the weather website. 

Related: Fishy rain to fire whirlwinds: The world's weirdest weather 

"One of the things I noticed from this is the dust started coming off the coast of Africa several days ago, in fact maybe over a week ago," Kottlowski told AccuWeather. "And it's still coming. It's almost like a prolonged area of dust."

The huge Saharan dust cloud formed June 13, when strong atmospheric updrafts over the Sahara were picked up by easterly winds, which blew the dust cloud west over the Atlantic, according to NASA.

Data collected by instruments aboard NASA's Suomi National Polar-orbiting Partnership (NPP) satellite show the dust cloud's enormity. Colin Seftor, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, used that data to create an animation of the plume. 

"This is the most significant event in the past 50 years," Pablo Méndez-Lázaro, an environmental health specialist at the University of Puerto Rico, told the AP. "Conditions are dangerous in many Caribbean islands," including in Antigua and Trinidad & Tobago, he said.

Dust from the Sahara plays an important role on the other side of the Atlantic Ocean; it builds beaches in the Caribbean and fertilizes soil in the Amazon rainforest during June, July and sometimes early August, according to NASA. The current cloud, however, is also affecting air quality, prompting health officials to tell people to stay indoors and use air filters, the AP reported. 

Saharan dust can also suppress tropical storms. "It keeps a lid on the atmosphere and brings dry air into anything that may try to develop, which is very detrimental for tropical development which relies on warm, moist air," Alan Reppert, a senior meteorologist at AccuWeather told the site.

Even so, this cloud likely won't affect the Atlantic hurricane season, which often peaks in August, September and October.

"Dust tends to be much less of a problem during the heart of the hurricane season," Kottlowski told Acuweather. 

To see a 10-day computer model forecast (as of June 22) of the dust cloud, check out this graphic tweeted by the National Weather Service.

The huge dust cloud will likely reach the Texas coast on Thursday (June 24) and cover the entire Gulf Coast by this weekend, Kottlowski said. The poor air quality this Saharan dust will bring could exacerbate the COVID-19 situation, according to an April study from the Netherlands. The study, published by the World Bank, suggests that areas with increased atmospheric particulate matter (that is, air pollution) have a higher incidence of the COVID-19 respiratory disease. 

"The estimates suggest that expected COVID-19 cases increase by nearly 100% when pollution concentrations increase by 20%," the researchers wrote in the study.

• Images: Amazing shots of storms light up weather photo contest 
• 2 stunning photos catch monster thunderstorm's approach 
• Photo: Massive ice balls along Lake Michigan

Originally published on Live Science.

Hundreds of stone structures dating back thousands of years have been discovered in the Western Sahara, a territory in Africa little explored by archaeologists.

The structures seem to come in all sizes and shapes, and archaeologists aren't sure what many of then were used for or when they were created, archaeologists report in the book "The Archaeology of Western Sahara: A Synthesis of Fieldwork, 2002 to 2009" (Oxbow Books, 2018).

About 75 percent of the Western Saharan territory, including most of the coastline, is controlled by Morocco, while 25 percent is controlled by the Sahrawi Arab Democratic Republic. Before 1991, the two governments were in a state of war. [See Photos of the Stone Structures in Western Sahara]

Between 2002 and 2009, archaeologists worked in the field surveying the landscape and doing a small amount of excavation in the part of Western Sahara that is controlled by the Sahrawi Arab Democratic Republic. They also investigated satellite images on Google Earth, they wrote in the book.

"Due to its history of conflict, detailed archaeological and palaeoenvironmental research in Western Sahara has been extremely limited," wrote Joanne Clarke, a senior lecturer at the University of East Anglia, and Nick Brooks, an independent researcher.

"The archaeological map of Western Sahara remains literally and figuratively almost blank as far as the wider international archaeological research community is concerned, particularly away from the Atlantic coast," wrote Clarke and Brooks, noting that people living in the area know of the stone structures, and some work has been done by Spanish researchers on rock art in Western Sahara.

Mysterious structures

The stone structures are designed in a wide variety of ways. Some are shaped like crescents, others form circles, some are in straight lines, some in rectangular shapes that look like a platform; some structures consist of rocks that have been piled up into a heap. And some of the structures use a combination of these designs. For instance, one structure has a mix of straight lines, stone circles, a platform and rock piles that altogether form a complex about 2,066 feet (630 meters) long, the archaeologists noted in the book.

Though the archaeologists are unsure of the purpose of many of the structures, they said some of them may mark the location of graves. Little excavation has been done on the structures, and archaeologists have found few artifacts that can be dated using a radiocarbon method. Among the few excavated sites are two "tumuli" (heaps of rock) that contain human burials dating back around 1,500 years.

Research suggests that Western Sahara was once a wetter place that could sustain more animal life than it does today. Archaeologists documented rock art showing images of cattle, giraffe, oryx and Barbary sheep while environmental researchers found evidence for lakes and other water sources that dried up thousands of years ago.

Security problems

At present, security problems in the region mean that fieldwork has stopped, Clarke and Brooks told Live Science. The terrorist group al-Qaeda in the Islamic Maghreb operates in the desert regions near Western Sahara, and in 2013 they kidnapped two Spanish aid workers at a refugee camp in Tindouf, Algeria, just across the border from Western Sahara.

While the Sahrawi people and Sahrawi Arab Democratic Republic strongly oppose the terrorist group, it's extremely difficult for authorities to effectively patrol the vast desert areas where the stone structures are located, Clarke and Brooks said. This means archaeologists can't work there safely right now. This problem is not unique to Western Sahara, as the security risks posed by terrorist and extremist groups in the region mean that archaeologists can't work in much of North Africa right now, they said.

• Photos: Aerial Views of Ancient Stone Structures in Saudi Arabia
• Gallery: Aerial Photos Reveal Mysterious Stone Structures
• The 25 Most Mysterious Archaeological Finds on Earth

Originally published on Live Science.

The Sahara is the world's largest hot desert, but parts of it could be made green if massive solar and wind farms set up shop there, a new study finds.

These farms could increase rain in the Sahara, especially in the neighboring Sahel region, a semiarid area that lies south of the giant desert, the researchers said in the study, which was published online Sept. 7 in the journal Science.

"This increase in precipitation, in turn, leads to an increase in vegetation cover, creating a positive feedback loop," study co-lead researcher Yan Li, a postdoctoral researcher in natural resources and environmental sciences at the University of Illinois, said in a statement.

Researchers already knew that wind and solar farms can increase the heat and humidity in the areas immediately around them. But this study is among the first to model how wind and solar farms would affect the Sahara, all while considering how growing green plants and trees would respond to these changes, said Li, who started the study while a postdoctoral researcher in the Department of Atmospheric and Oceanic Science at the University of Maryland. [The 10 Biggest Deserts on Earth]

"Previous modeling studies have shown that large-scale wind and solar farms can produce significant climate change at continental scales," Li said. "But the lack of vegetation feedbacks could make the modeled climate impacts very different from their actual behavior."

Li and his colleagues simulated what would happen if wind and solar farms covered more than 3.4 million square miles (9 million square kilometers) of the Sahara. On average, the wind farms would generate about 3 terawatts, while the solar farms would generate 79 terawatts of electrical power in one year, they found.

That's a lot of energy. One terawatt can power about 10 billion 100-watt light bulbs simultaneously. "In 2017, the global energy demand was only 18 terawatts, so this is obviously much more energy than is currently needed worldwide,” Li said.

The model also showed that wind farms caused localized air temperatures to warm.

"Greater nighttime warming takes place because wind turbines can enhance the vertical mixing and bring down warmer air from above," the researchers wrote in the study. Rain also increased as much as 0.01 inches (0.25 millimeters) per day, on average, in areas with wind farms, the researchers found.

"This was a doubling of precipitation over that seen in the control experiments," Li said.

The Sahel would see even more rain; an increase of 0.04 inches (1.12 mm) a day in areas with wind farms, which would help vegetation there grow, the researchers said. That translates to an increase of between 8 and 20 inches (200 and 500 mm) of rain a year in the Sahel, enough that it would not be classified as a desert. (Deserts, by definition, are areas that receive less than 10 inches (250 mm) of annual rainfall.)

The solar farms would also have a positive effect on temperature and rainfall, the researchers noted.

"We found that the large-scale installation of solar and wind farms can bring more rainfall and promote vegetation growth in these regions," study co-lead researcher Eugenia Kalnay, a distinguished professor in the Department of Atmospheric and Oceanic Science at the University of Maryland, said in the statement. "The rainfall increase is a consequence of complex land-atmosphere interactions that occur because solar panels and wind turbines create rougher and darker land surfaces."

If this model ever becomes a reality, "the increase in rainfall and vegetation, combined with clean electricity as a result of solar and wind energy, could help agriculture, economic development and social well-being in the Sahara, Sahel, Middle East and other nearby regions," Safa Motesharrei, a systems scientist at the University of Maryland, said in the statement.

"The Sahara has been expanding for some decades, and solar and wind farms might help stop the expansion of this arid region," Russ Dickerson, a leader on air quality research and a professor at the Department of Atmospheric and Oceanic Science at the University of Maryland who was not involved in the study, said in a statement. "This looks like a win-win to me."

Original article on Live Science.

The dramatic contrast between the burnt-orange dunes and the dull-blue hills of the Sahara Desert in northern Africa makes for a stunning view from the International Space Station, as seen in a new image shot from the ISS.

This gorgeous landscape shows the border between Algeria and Libya, which is one of the driest parts of the Sahara Desert, according to NASA's Earth Observatory. For scale, note that the dune portion of the image is about 60 miles (100 kilometers) long.

Large dune fields, such as the one shown here in Algeria, are known to geologists as "ergs" — the Arabic word for giant sandy expanses. This erg, called the Grand Erg Oriental, includes hundreds of bumpy dunes that cover a vast area of about 370 miles by 124 miles (600 by 200 km), the Earth Observatory reported. That's a region larger than 22 million football fields. [Cholla Photos: See these Amazing Desert Cacti]

On the hilly, bluish side of the image, notice the branching waterways. These channels are usually dry, but when it rains they carry the water to the edge of the erg.

The whitish blotch in the hilly terrain is a dry desert lake. The straight lines are human-made roads. In the top middle, the Libyan town of Ghadames, population 10,000, appears as a dark-blue dot. The walled-off town is a United Nations' World Heritage site.

The photo was taken through the window of the ISS by the Sally Ride EarthKAM (Earth Knowledge Acquired by Middle-school students) on Oct. 31, 2017. The astronaut Sally Ride (1951-2012), the first American woman in space, started the program so that middle-school students could ask astronauts aboard the ISS to take pictures of different regions on Earth.

Original article on Live Science.

The Sahara — the world’s biggest hot desert — is getting even bigger. In fact, it is currently about 10 percent larger than it was nearly a century ago, and scientists suggest that climate change is partly responsible.

In a new study, researchers examined rainfall data gathered across Africa, consulting records dating back to 1920 and noting how changing conditions affected regions around the boundaries of the great desert.

They discovered that while some natural climate cycles could partly explain reduced rainfall and desert expansion southward, human-driven climate change is also playing a part. And if climate change continues unchecked, the Sahara's slow growth will likely continue, the study authors reported. [The Sahara: Facts, Climate and Animals of the Desert]

Previously, scientists had explored the Sahara's expansion by examining satellite data dating back to the 1980s. This study, which was supported by the U.S. National Science Foundation, is the first to analyze long-term trends in rainfall and surface air temperature over a timescale of nearly an entire century, the study's lead author, Natalie Thomas, a doctoral candidate in atmospheric and oceanic science at the University of Maryland, told Live Science.

Deserts are defined as places on Earth that receive less than 10 inches (25 centimeters) of rainfall per year, according to the U.S. Geological Survey (USGS). With a surface area of about 3.6 million square miles (9.4 million square kilometers), the Sahara is the third-largest desert in the world. Only the cold deserts are bigger: icy Antarctica's frozen desert spans about 5.5 million square miles (14.2 million square km), and the Arctic desert covers around 5.4 million square miles (13.98 million square km), USGS reported.

"A strong expansion"

The study authors originally set out to examine seasonal cycles of temperature and rainfall across Africa, consulting data spanning 1920 to 2013. But their attention was quickly drawn to trends of decreasing precipitation in the Sahel, a semiarid region linking the Sahara to the savannas of Sudan. By looking at this more closely, they hoped to discover how rainfall trends might be linked to the Sahara's growth over time, according to Thomas.

To a certain extent, many deserts' boundaries expand and contract seasonally, as conditions fluctuate between wetter or drier. But the researchers found that there has been "a strong expansion" of the Sahara within the 20th century, Thomas said.

Depending on the season, the Sahara experienced growth of at least 11 percent, and it grew by as much as 18 percent during the driest summer months, according to data collected over roughly 100 years. Over the course of a century, it steadily expanded to become about 10 percent bigger than it was in 1920, the study authors reported.

Much of the Sahara's overall size increase can be explained by climate cycles driven by anomalies in sea-surface temperatures. These cyclical changes in turn affect surface temperatures and precipitation on land, and their impact can last for decades, according to the study.

Decades of drought

One such cycle, the Atlantic Multidecadal Oscillation (AMO), entered what is known as a "negative phase" — with cooler-than-average sea-surface temperatures — in the 1950s, bringing heat and dry conditions to the Sahel region and fueling a drought that lasted until the 1980s, Thomas said.

Using statistical methods, the scientists compensated for the effects of the AMO on average rainfall, and thereby calculated how much of the Sahara's growth could be explained by the dryness that the cycle's negative phase produces. They estimated that the AMO accounted for about two-thirds of the desert's expansion — but one-third of the Sahara's remaining growth was likely the result of climate change.

The researchers' findings point to changes that occur over decades rather than in a single year, and that makes it hard to predict exactly how the Sahara's continued growth could affect the wildlife and people near its changing borders. But as the places where humans grow food become increasingly drier, some areas could become more vulnerable to drought, bringing a greater risk of famine to the people who live there, Thomas said.

The findings were published online today (March 29) in the Journal of Climate.

Original article on Live Science.

Egyptian titanosaur

Researchers in Egypt just uncovered a newly identified long-necked dinosaur known as Mansourasaurus shahinae. This is only the sixth dinosaur species to be discovered in Egypt.

M. shahinae sheds light on dinosaur evolution on the different continents. Even though it was discovered in Egypt, M. shahinae had more in common with dinosaurs uncovered in Europe than it did with dinosaurs found in southern Africa. [Read more about the Egyptian dinosaur]

Skeletal reconstruction

A skeletal reconstruction of the roughly 80-million-year-old M. shahinae. The colored bones are those that are preserved in the original fossil; other bones are based on those of closely related dinosaurs.

Dinosaur jaw

The left lower jawbone of the newly discovered titanosaurian dinosaur M. shahinae. The fossil was found in rock of the Cretaceous-age Quseir Formation in the Dakhla Oasis, in Egypt.

Careful excavation

Student Mai El-Amir (left) and study lead researcher Hesham Sallam (right), of Mansoura University, prepare to glue bones of the new titanosaurian dinosaur M. shahinae in the field.

Team photo

The all-Egyptian field team from the Mansoura University Vertebrate Paleontology initiative that found and collected the new titanosaurian dinosaur M. shahinae with the plaster "jackets" containing the fossil skeleton at the discovery site. From left to right: Hesham Sallam, Yassin El Saay, Farahat Ibrahim, Mai El-Amir, Sanaa El-Sayed, Iman El-Dawoudi and Sara Saber.

Forearm bone

Mansoura University student Mai El-Amir brushes an ulna (forearm bone) that likely belongs to the newly identified titanosaurian dinosaur M. shahinae.

Teamwork

Students Mai El-Amir and Sara Saber excavate ribs and other bones of the newly discovered titanosaurian dinosaur M. shahinae in the Sahara Desert in Egypt. The team's field tents are visible in the background.

[Read more about the Egyptian dinosaur]

The sandstorm

Despite a ferocious sandstorm, several members of the field team do their best to collect bones of M. shahinae.

Female field team

The four female members of the all-Egyptian field team that discovered M. shahinae. From left to right: Mai El-Amir, Iman El-Dawoudi, Sara Saber and Sanaa El-Sayed. The "jackets" contain the fossil skeleton.

Jawbone

M. shahinae's lower jawbone, shown here from five perspectives.

Shoulder bone

The right scapulocoracoid, or shoulder bone, of M. shahinae, as seen from the side. The dashed line indicates the probable extent of the missing portion and is based on complete scapulocoracoids of other titanosaurs, the researchers said.

Future paleontologists

Mansoura University vertebrate paleontology student Iman El-Dawoudi shows M. shahinae's lower jaw to two budding Egyptian paleontologists.

International peers

Study co-researchers Eric Gorscak (left), Iman El-Dawoudi (center) and Matt Lamanna (right) study the lower jaw of M. shahinae.

"It's absolutely rare to find dinosaurs in Egypt, though that situation is beginning to change, thanks mostly to the efforts of my friend/collaborator Hesham Sallam and his team," Lamanna told Live Science in an email.

[Read more about the Egyptian dinosaur]

Egypt is known for its magnificent pyramids and powerful pharaohs, but now the country is gaining fame among paleontologists, especially now that an international team has uncovered the remains of an 80-million-year-old dinosaur the size of a school bus that had bony plates embedded in its skin during its lifetime.

Egyptian researchers discovered the newfound sauropod — a long-necked, long-tailed herbivorous dinosaur named Mansourasaurus shahinae — in the Sahara Desert. The find is remarkable, given the rarity of dinosaur fossils in Africa from the Late Cretaceous (100 million to 66 million years ago), the period of time just before the 6-mile-long (10 kilometers) asteroid slammed into Earth and killed the nonavian dinosaurs, the researchers said.

"Africa remains a giant question mark in terms of land-dwelling animals at the end of the age of dinosaurs," study co-researcher Eric Gorscak, a postdoctoral research scientist at The Field Museum in Chicago, who started the project as a doctoral student at Ohio University, said in a statement. "Mansourasaurus helps us address long-standing questions about Africa's fossil record and paleobiology — what animals were living there, and to what other species were these animals most closely related?" [See Images of the Egyptian Dinosaur] 

His co-researcher, Matt Lamanna said his "jaw hit the floor," when he saw photos of M. shahinae's fossils. "This was the Holy Grail — a well-preserved dinosaur from the end of the age of dinosaurs in Africa — that we paleontologists had been searching for for a long, long time," Lamanna, a paleontologist at the Carnegie Museum of Natural History, in Pittsburgh, said in the statement.

Were African dinosaurs isolated?

The discovery of M. shahinae reveals how dinosaurs evolved to be different from one another as the continents split apart. During the Triassic and Jurassic periods, the continents were joined together as the supercontinent Pangaea. Scientists know that the continents began to split apart during the Cretaceous, but it's unclear how well connected Africa was to Europe and the Southern Hemisphere landmasses, the researchers said. Without this knowledge, it's challenging to know if Africa's animals were completely cut off from the rest of the world, they said.

Luckily, studying ancient animal fossils can help scientists unravel this mystery. For instance, if Africa still had land connections to Europe during the Cretaceous period, its animals would likely have similar anatomies to those on neighboring landmasses. But if the continents were fully separated, the animals in Africa likely would have evolved different characteristics, the researchers said.

Late Cretaceous dinosaur fossils from Egypt, however, are challenging to find. Unlike the exposed, rocky regions that make dinosaur hunting easy in the U.S. Rocky Mountains, the Gobi Desert in Mongolia or the Patagonia region of Argentina and Chile, much of the land in Africa is covered with lush vegetation, making it difficult for paleontologists to know where to dig (i.e., no bones poking out of the ground).

That's why "Mansourasaurus shahinae is a key new dinosaur species and a critical discovery for Egyptian and African paleontology," Gorscak said.

Indeed, M. shahinae is more closely related to the dinosaurs of Europe and Asia than it is to those in southern Africa or even South America, according to an analysis done by lead study researcher Hesham Sallam, a lecturer in the Department of Geology at Mansoura University in Egypt, and his colleagues. This suggests that some dinosaurs were moving between Africa and Europe during the Late Cretaceous, Sallam said in the statement. [Gallery: Reconstructed Dinosaur 'Chase']

Egyptian titanosaur

Researchers named Mansourasaurus shahinae after Mansoura University and Mona Shahin, who helped develop the Mansoura University Vertebrate Paleontology (MUVP) initiative in 2010 to educate Egyptian vertebrate paleontologists. [Titanosaur Photos: Meet the Largest Dinosaur on Record] 

M. shahinae belongs to Titanosauria, a group of enormous sauropods — including Argentinosaurus, Dreadnoughtus and Patagotitan — that lived around the world during the Cretaceous period, the researchers said. However, although M. shahinae is the most complete dinosaur specimen from the Late Cretaceous of Egypt, it wasn't the largest titanosaur on record; it weighed about as much as an African bull elephant, the researchers said. (That's more than 10 times less than Patagotitan, which likely weighed a whopping 69 tons, or 62 metric tons, Live Science previously reported.)

Besides M. shahinae, there are just five other dinosaur species known from Egypt: huge predatory dinosaurs — Bahariasaurus ingens, Carcharodontosaurus saharicus and (most famously) Spinosaurus aegyptiacus, a dinosaur that could likely swim — and two titanosaurian sauropods — Aegyptosaurus baharijensis and Paralititan stromeri, Lamanna told Live Science.

However, with the exception of the newfound M. shahinae, "all of these Egyptian dinosaurs are about 95 million years old," Lamanna told Live Science. "At about 80 million years old, our new beastie is the only named dinosaur from the last 30 million years of the Cretaceous in Egypt."

The study was published online today (Jan. 29) in the journal Nature Ecology and Evolution.

Original article on Live Science.

Satellite photos show parts of Africa's Sahara Desert blanketed in snow following a rare winter storm earlier this month.

The European Space Agency's (ESA) Copernicus Sentinel-2 satellite captured stunning views of the snow-covered dunes in northwest Algeria, on the edge of the Sahara Desert — an area known to be one of the hottest places on Earth, according to a video from ESA.

The images, taken on Jan. 8, revealed that some areas of the desert were covered in up to 15 inches (40 centimeters) of snow, which fell across the arid region on Jan. 7, according to the video. [The Sahara Desert: Facts, Climate & Life]

"Most of the snow had melted by the end of the next day, but luckily, the Sentinel-2A satellite happened to be in the right place at the right time to record this rare event from space," ESA representative Kelsea Brennan-Wessels said in the video. 

Specifically, the satellite images show that snow fell on the lower Saharan Atlas mountain range. While temperatures in this area can drop significantly at night, snowfall is very unusual in the Sahara Desert because the air is so dry. 

In fact, the recent snowfall marks only the third time in 37 years that scientists have recorded powdered snow in this part of the desert, according to the ESA video. The previous storms that were recorded occurred in February 1979 and December 2016.

The Copernicus Sentinel-2 satellites are largely used to track changes in Earth's land and vegetation. The recent satellite images show that there is very little flora in the region, according to the video. 

This rare Sahara snowfall was also photographed by the Landsat 8 satellite (a collaboration between NASA and the U.S. Geological Survey) on Jan. 8. The Landsat 8 images revealed a snow accumulation of between 4 and 12 inches (10 to 30 cm) in the desert near the northern Algerian town of Aïn Séfra, according to a statement from NASA. 

Such snowfall is much more common in higher altitudes of the Sahara, including the High Atlas mountains in Morocco, which also saw a substantial amount of snow in February 2012 and January 2005, NASA officials said in the statement.  

Follow Samantha Mathewson @Sam_Ashley13. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

Belief in witchcraft is linked to a lack of trust for people in sub-Saharan Africa, new research finds. And that lack of social trust may be a barrier to economic development in struggling nations.

In regions where witchcraft belief is high, people are less likely to trust others, including their family, neighbors and local institutions, American University economist Boris Gershman reports in the May issue of the Journal of Development Economics. "What's more, the children of immigrants from countries with high prevalence of witchcraft beliefs are more distrusting than children of immigrants from other countries," Gershman found, suggesting that such beliefs may contribute to the formation of persistent antisocial attitudes.

"Economists and other social scientists have found a positive role of things like trust and cooperation in fostering business transactions, economic growth, trade and a variety of positive socioeconomic outcomes," Gershman told Live Science. "If witchcraft beliefs indeed contribute to the erosion of social capital, this is the channel through which they may adversely affect economic development." [The Truth About 13 Interesting Superstitions]

Witchcraft and trust

Gershman's analysis focused on data drawn from a Pew Forum on Religion and Public Life survey conducted in 2008 and 2009 with more than 25,000 people in 19 sub-Saharan countries. The surveys revealed that about 57 percent of respondents believed in witchcraft.

Local beliefs in witchcraft vary, Gershman wrote, but the common thread is that people believe that misfortune (and disease, including HIV) are the result of malevolent spells cast by others. Case studies across sub-Saharan Africa and in other societies with witchcraft beliefs find that these beliefs spread fear in two ways, Gershman said. First, people may fear being bewitched. Second, and possibly more frightening for many, is the fear of being accused of witchcraft, which can sometimes lead to murder. These fears can prevent people from cooperating with one another.

"For example, in one case, people were saying they refuse to provide food assistance to their neighbors, because they were fearing that if something goes wrong, if their neighbors get sick, they were fearing witchcraft accusations," Gershman said. The more common witchcraft beliefin a region, the less likely residents were to engage in charitable giving, Gershman found.

Gershman's analysis controlled for demographic and historical factors that might influence both witchcraft belief and trust, but the results are still correlational. They can't prove that witchcraft belief directly makes people less trusting. But combined with ethnographic case studies, the new research bolsters the idea that witchcraft beliefs really do breed distrust, he said. However, there is likely a feedback loop at play.

"I think it's quite likely that there is this self-reinforcing relationship between witchcraft beliefs and accusations and low social capital," Gershman said, using economics lingo for networks of trusting relationships. "Witchcraft beliefs and accusations erode trust, and eroded trust makes it more likely that witchcraft accusations will continue." [What's Witchcraft? 6 Misconceptions About Wiccans]

About 70 percent of people in the Pew survey said that one "can't be too careful" when dealing with others, picking that answer over "most people can be trusted." The variation in witchcraft belief accounted for about 7 percent of the variation in trust within countries.

The cost of witchcraft

Notably, other superstitious beliefs were not linked with trust, Gershman found. Believing in angels, miracles, shamans or taking a literal view of religious concepts like heaven or hell didn't correlate with people's trust levels.

The confluence of witchcraft and religious belief was somewhat complex, however. The vast majority of respondents — well over 90 percent — identified as Christian or Muslim, Gershman said. But in both religious groups, around 60 percent of people said they also believed in witchcraft.

"What we see is obviously a coexistence of what we think of as classical religion and local beliefs," Gershman said.

There's a strong body of research suggesting that religions with high, moralizing gods promote cooperation, Gershman said. His study hints at the converse: Traditional belief in witchcraft stifles cooperation.

There may be reasons why witchcraft beliefs persist, Gershman said. They can act as an equalizing agent in societies without a welfare state or any mechanism for redistributing wealth; if a person gets too high and mighty, his fellow villagers might accuse him of witchcraft and strip him of his assets. But the survey and ethnographic data suggest that this comes at a high cost to development, Gershman said.

The results would likely apply to other societies where witchcraft beliefs are prevalent, he said. In another analysis, Gershman used data from 186 preindustrial societies around the world and found that those in which witchcraft was seen as an important cause of disease were also those in which parents encouraged toughness and aggression over trust, generosity and honesty. This may be an effort to prevent kids from being either witchcraft victims or alleged witches, Gershman said. A look at another round of data from the European Social Survey revealed that the children of immigrants to Europe from witchcraft-believing areas were less trusting than children of immigrants from elsewhere, bolstering the link between witchcraft belief, parenting and trust.

Witchcraft belief is something that international aid agencies need to take into account when planning economic development programs, Gershman said.

"Imagine you provide people with some new technology and some people adopt it and other people don't, or some people are more successful than others, which creates a disparity in harvest," Gershman said. "This, for a society in which witchcraft beliefs are prevalent, is a possible situation for conflict and accusations."

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

One ant species in the Sahara Desert is covered by a silvery sheen of body hair that acts as a wearable sun shield for the creatures, a new study finds.

The silvery hairs completely reflect the light like mirrors, preventing the ants from absorbing too much heat. That may help to explain how the Saharan silver ants can stay cool when temperatures in the arid region reach a blistering 122 degrees Fahrenheit (50 degrees Celsisus).

"The ability to reflect solar radiation by means of total internal reflection is a novel adaptive mechanism in desert animals, which gives an efficient thermal protection against the intense solar radiation," study co-author Serge Aron, an evolutionary biologist at the University Libre de Bruxelles in Belgium, said in a statement. "To the best of our knowledge, this is also the first time that total internal reflection is shown to determine the color of an organism." [See Photos of Crazy Ants]

Hot weather, cool bodies

The Sahara is the hottest large desert on the planet and one of the most punishing environments for any creature to withstand. Comprising millions of square miles of sand dunes that cover 10 African countries, the area is inhabited mostly by myriad small and scurrying creatures, such as rodents, snakes and scorpions.

One of these native creatures is the Saharan silver ant. These shiny ants are known to be well-adapted to Sahara's withering heat. Scientists had shown in past research that the ants' silver hairs played a role in preventing overheating, but they weren't sure exactly how that worked.

To answer that question, Quentin Willot, an evolutionary biologist at the University Libre de Bruxelles, Belgium and colleagues took a very close look at the ants' hairs. The team analyzed the path of reflected light inside the silvery hairs under a scanning electron microscope, then compared that to the light path in the ants that had been shorn of their hairs.

Those ants sporting a luxurious patch of hair were 10 times as reflective as their shaved brethren. What's more, the team found the silvery hairs formed a kind of prism, which forced light rays entering the hair to be completely reflected off the bottom surface, rather than passing through and entering the ant's body. The prism effect occurs thanks to the triangular cross-section of the hairs, the researchers reported yesterday (April 13) in the journal PLOS ONE.

These adaptations seem to work: The silver-haired ants kept their bodies up to 4 degrees F (2 degrees C) cooler than the shaved ants did.

Though other ants and related species also sport protective bristles, most have cylindrical or plate-like cross-sections, meaning the internal reflection achieved by the Saharan silver ant may be unique, the researchers said.

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

The roughly 8,000-year-old "hands" painted on a rock wall in the Sahara Desert aren't human at all, as researchers originally thought, but are actually stencils of the "hands" or forefeet, of the desert monitor lizard, a new study finds.

These tiny lizard hands are intermingled with paintings of human adult hands, which ancient rock artists stenciled around using red, yellow, orange and brown pigments, the researchers said.

It's unclear why these ancient people used both human and lizard hands as stencils, but the finding may provide clues about the mysterious people who lived in the Sahara about 8,000 years ago, the researchers said. [Gallery: See Amazing Images of Cave Art]

"It completely changes the way we think about prehistoric people," said lead study researcher Emmanuelle Honoré, a research fellow at the McDonald Institute for Archaeological Research at the University of Cambridge in the United Kingdom. "We never imagined they had such complex practices in that area at that time."

Researchers discovered the cave, called Wadi Sūra II, in the Egyptian part of the Libyan Desert in 2002. The cave is located about 6 miles (10 kilometers) from the renowned Cave of Swimmers (officially known as Wadi Sūra I), a site discovered in 1933 and made famous by the popular 1992 novel "The English Patient."

The Wadi Sūra II cave, which can also be described as a shelter because it's more of a rocky overhang, is about 66 feet (20 meters) long and 26 feet (8 m) deep. Roughly 900 stencil paintings of arms, feet, discs, sticks and tiny and large hands cover the rock walls inside the cave.

Honoré was stunned the first time she walked into Wadi Sūra II in 2006. "I immediately saw those tiny hands among [nearly] thousands of paintings," she said.

In earlier studies, researchers hypothesized that the large and small hand paintings were stenciled around adult and baby hands. Yet, shortly after looking at the 13 "baby" hand drawings, Honoré concluded that they weren't human.

For one thing, they were too small to belong to a human infant, she said. Moreover, the digits were pointy and "very long and very thin," Honoré said. In contrast, human babies have fingers that are roughly the same length as their palms.

"After a few years, I was obsessed by this idea [that they weren't human]," Honoré told Live Science. "It came back to my mind every day, and I decided I had to test it."

Handy experiment

Initially, Honoré compared the hands of her newborn niece and cousins to the rock art. A simple comparison showed that the ancient prints were too small to be human, but she needed a larger sample of hands to say for sure. [Photos: 'Winged Monster' Rock Art in Black Dragon Canyon]

So Honoré worked with the Lille University Hospital in northern France, and ended up getting the hand measurements of 25 preterm babies and 36 typical babies who survived birth.

"We were really surprised; all of the parents agreed to [let their babies] take part in the experiment," Honoré said. "They were very enthusiastic that their babies could contribute to a scientific study." 

Honoré and her colleagues also measured 11 of the tiny hands at the Wadi Sūra II site. (The other two were incomplete and difficult to measure, she said.) In addition, they measured 30 of the large hands at Wadi Sūra II and 30 hands from living adults, and found that they matched well, she said.

But several parameters indicated that the tiny hands were not human. Though the stenciled fingers were long, overall the hands were small — just 1.8 inches (4.5 centimeters) from the base of the palm to the end of the middle finger. That's much smaller than a human baby hand, which measures an average of 2.4 inches (6.2 cm) long, she said

"We were completely shocked by our own research because it brought up the question — if it's not babies, what is it?" Honoré said.

Hand detective

At first, Honoré thought the tiny hands belonged to a small monkey. But none of the thousands of monkey hand pictures she researched looked like those on the wall at Wadi Sūra II. Then, when she was doing research at a crocodile farm in Zambia, she realized that the prints belonged to a reptile.

The front feet of the desert monitor lizard (Varanus) had the closest match to the wall paintings, she found. A baby crocodile (Crocodylus) was another possibility. However, crocodiles likely didn't live in the desert at that time, so a person would have needed to transport one over from the Nile or another watery region, Honoré said.

Other prehistoric cultures used animals as stencils for their rock art. For example, the Aboriginal people used emu foot stencils in the Carnarvon Gorge and Tent Shelter in Australia, and choike/nandu (birds in the genus Rhea) stencils are in the rock art at La Cueva de las Manos in Argentina, the researchers wrote in the study.

It's unclear why the ancient people at Wadi Sūra II used reptile hands as stencils, but Honoré said she's working on a new study that analyzes possible reasons. [History's 10 Most Overlooked Mysteries]

"I think we have to remain a bit prudent," she said. "We have to explore all of the hypotheses without taking anything for granted."

Ancient art made from hand stencils is not too prevalent in the Sahara. This makes the new study an important one, said French rock expert Jean-Loïc Le Quellec, who was the first to hypothesize that the tiny hands were stencils of human baby hands, but was not involved in the new research.

"I am delighted to see that the statistic[al] analysis by the authors clearly demonstrates that these tiny hands are not human," Le Quellec told Live Science in an email. "I must say that I suspected that they were reptile hands, but I didn't publish that idea in our book on Wadi Sura, because my co-authors were considering it as fantasy assumption."

The findings are published in the April 2016 issue of the Journal of Archaeological Science: Reports.

Follow Laura Geggel on Twitter @LauraGeggel. 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.

Winds sculpt the landscape of the Saharan coastline of West Africa. Here, the Atlantic Ocean meets arid land, and northerly winds push the sand in streaks parallel to the coast.

This image, released today (June 30) by NASA's Earth Observatory, was taken from the International Space Station on May 20. The astronaut's-eye-view reveals puffy clouds off the coast and ripplelike internal waves headed toward the shore. Internal waves are waves that occur almost entirely below the ocean's surface. Warm, less-salty water moves through colder, saltier water; these masses of water can be hundreds of feet tall. Some are more than 550 feet (170 meters) in height, according to researchers from MIT who are studying the phenomenon.

On the surface, internal waves often leave a footprint only a few inches tall, but sunglint, or sunlight reflecting off the surface, highlights these waves in photographs from space, according to NASA's Earth Observatory.

Other desert features stand out in this image. Silvery splotches reveal salt flats called sabkhas. Sand streaks parallel to the coast are caused by winds blowing from north to south, scouring the desert as they travel. Right off the coast, waves erode the sandy shore, staining the near-shore water aqua. 

As alien as this desert world may seem, the mark of human hands is visible in this photograph. On the left of the image, a light line running from the inland to the coast is a phosphate transport corridor. Roads, railways and conveyer belts move phosphate along this corridor, for use in making phosphorus, a major ingredient in fertilizers. Phosphorus is also used to make steel and to make compounds used in the manufacture of flame retardants, plastics and pesticides.

Editor's Note: If you have an amazing nature or general science photo you'd like to share for a possible story or image gallery, please contact managing editor Jeanna Bryner at LSphotos@livescience.com.

Follow Stephanie Pappas on Twitterand Google+. Follow us @livescience, Facebook& Google+. Original article on Live Science.

Some 100,000 years ago, three large rivers snaked through what is today the bone-dry Sahara Desert, new research suggests.

The rivers, now buried, would have created pockets of green areas and provided water in a parched landscape. That, in turn, could have allowed ancient humans to migrate from across the Sahara and then out of Africa, according to research detailed today (Sept. 11) in the journal PLOS ONE.

"These rivers were big," said study co-author Thomas Coulthard, a hydrologist at the University of Hull in England. "They were about the same as the Missouri or the Rhine or even the Nile when it's low flow." [Sahara to Patagonia: The 10 Biggest Deserts On Earth]

Out of Africa

Some scientists think humans left central Africa between 125,000 and 100,000 years ago. (A recent study suggested the migration happened as early as 62,000 years ago.) Humans may have first migrated to the west coast of Africa before traveling along the coastline to the Middle East, or they may have moved along the Nile or around the Arabian Peninsula. Those routes would have required thousands of miles of travel.

Traveling through the Sahara Desert would have been a more direct route for people in Central Africa. But the Sahara Desert today is one of the driest places on Earth, with half of the Sahara receiving less than an inch of rainfall a year, making any trek arduous.

But archaeological remains suggest the Sahara was once settled, and some scientists thought a few small rivers threading through the desert might have once been large and continuous.

Ancient rivers

To test out that idea, Coulthard and his colleagues created a computer model of the magnitude of monsoons in a region of the Sahara spanning 4.6 million square miles (12 million square kilometers) as it existed about 100,000 years ago. At that time, the monsoon rains landed hundreds of miles north from where they fall now.

As a result, heavy rains fell on the north face of two Saharan mountain ranges, the Ahaggar and Tibesti mountains, which span portions of Algeria, Libya and Chad.

The model used topography to predict where the water would have flowed.

Even with high water loss due to evaporation and groundwater absorption, the researchers found that higher rainfall fed three small, mostly dry rivers — the Irharhar, Sahabi and Kufra — that were much larger than today and spanned the length of the Sahara. [The World's 10 Longest Rivers]

"It isn't a huge amount, but it's the amount of rainfall you might get in southern Spain," Coulthard told LiveScience.

These rivers would have provided green habitats to support people migrating from Africa, Coulthard said.

In fact, archaeologists have found stone tools dating to that time around the Irharhar River, Coulthard said. And archaeological finds may be hidden near the other two rivers.

"The area is covered in sand dunes and sand sea, so there's a whole raft of archaeological evidence that's just kind of buried there," Coulthard said. (Sand sea is a flat area of sand with no vegetation and really no physical features.)

True migration route?

The findings are reasonable and convincing, Paul Myers, an earth scientist at the University of Alberta in Canada, who was not involved in the study, wrote in an email.

"We know that orbital changes effect the monsoon and precipitation in this region. It has also been shown before that in other periods the Sahara has been quite wet," Myers said, referring to the slight changes to Earth's orbit over time.

But a Saharan route out of Africa is still unlikely, said Chris Stringer, an anthropologist at the Natural History Museum in London, who was not involved in the study.

"Even these river systems are some way from the route through the narrow area east of the Nile, which is going to lead them into Israel," Stringer told LiveScience.

After making it through the Sahara, migrating people still would have needed green areas to migrate east out of Africa, he said.

Instead, the findings could help explain how technological advances, such as the prevalence of red ochre paint, spread within Africa at the time, Stringer said.

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

Big deserts

Earth is a planet covered with habitable areas, but some of those locations are a little more hostile to life than others. In deserts, which generally are defined as areas that receive less than 10 inches (254 millimeters) of rain or snow annually, the plants and animals must subsist on this meager precipitation.

The world's 10 biggest deserts are found on just about every continent, many of them forming in the shadow of immense mountain ranges that block moisture from nearby oceans or bodies of water. They're often the site of unusual rock formations and, in some cases, amazing archaeological finds.

Chihuahuan Desert

175,000 square miles (282,000 square km)

Straddling the U.S.-Mexico border, the Chihuahuan Desert is bigger than the state of California, according to New Mexico State University. Parts of it are in the states of Texas, New Mexico and Arizona. Less than 9 inches (228 mm) of rainfall falls on average every year, according to the Chihuahuan Desert Education Coalition.

As with many other deserts worldwide, the Chihuahuan Desert formed in the rain shadow of both the Sierre Madre Occidental (on the west) and the Sierra Madre Oriental (on the east), which both stop water from the Pacific Ocean and the Gulf of Mexico from getting inland.

Underneath the desert and New Mexico's Guadalupe Mountains lies more than 300 caves. Those in at least one of those regions, Carlsbad Caverns National Park, were created after sulfuric acid penetrated the surrounding limestone.

Great Basin Desert

190,000 square miles (492,000 square km)

Unlike every other desert in the United States, the Great Basin is a "cold" desert — one where most of the precipitation falls as snow. Its geographic extent includes most of Nevada, part of Utah and parts of many surrounding states. Rainfall in the region ranges between 6 and 12 inches (150 and 300 mm) annually.

The desert came to be because it was in the rain shadow of the Sierra Nevada Mountains of eastern California, according to the National Park Service. The desert, in turn, also affects surrounding areas. Strong winds known as the Santa Ana often blow into Southern California after forming in areas of high pressure in the Great Basin.

The Great Basin is also home to some unusual rocks, such as some found in central Nevada in 2009 that were described as dripping like honey. The deformation is taking place due to changes in the Earth's mantle, which alters due to intense pressure and heat within Earth's surface. Heavier material in the lithosphere, as it warms up, sinks through the lighter mantle, trailing material after it.

Syrian Desert

200,000 square miles (518,000 square km)

The Syrian Desert is described as an "arid wasteland" by Merriam-Webster. Covering much of Iraq, Jordan, Saudi Arabia and Syria, the region is marked by lava flows and was an "impenetrable barrier" to humans until recent decades. Now, highways and oil pipelines cross the region, which receives less than 5 inches (125 mm) of rain annually, on average.

Humans were able to reach parts of it in ancient times, though. One area, now dubbed "Syria's Stonehenge," was discovered in 2009. It includes stone circles and possibly, tombs, according to a 2012 Discovery News report.

The Es Safa volcano field near Damascus is Arabia's largest volcanic field. The vents found in that area were active about 12,000 years ago, during the Holocene Epoch. More recently, a boiling lava lake was spotted in the region around 1850.

Great Victoria Desert

250,000 square miles (647,000 square km)

The Great Victoria Desert covers a great deal of Australia and is mostly made up of parallel dunes as well as some salt lakes, according to an atlas from the Government of South Australia. The dunes are mostly red sand that came from the Western Australian Shield, changing to white as one moves south due to sands coming from the coast.

The Australian government describes the region as one with "variable and unpredictable rainfall." Averaging out data between 1890 and 2005, rainfall is about 6.4 inches (162 mm) annually. Due to the harsh environment, most of the desert is split between Aboriginal lands, conservation areas and crown land, with no major cities.

One of the Outback's greatest ecological threats comes from camels, whose ancestors were imported from India, Afghanistan and Arabia during the 19th century for work in the desert. A 2013 BBC report said the approximately 750,000 feral camels drink an ordinate amount of water and also damage infrastructure. "Camels are almost uniquely brilliant at surviving the conditions in the Outback," said explorer Simon Reeve in the report. "Introducing them was short-term genius and long-term disaster."

Patagonian Desert

260,000 square miles (673,000 square km)

The Patagonian Desert is a large desert lying across much of Argentina. The desert and semi-desert area stretches from the Atlantic Ocean to the Andes, with mostly treeless plains, according to the Encyclopedia Britannica.

Like California's Death Valley, the Patagonian Desert lies in the "rain shadow" of a high mountain range — in Patagonia's case, the Andes. Some regions of the desert receive as little as 6 to 8 inches (160 to 200 mm) of rainfall a year, according to Dryland Climatology, a 2011 book by Florida State University meteorologist Sharon E. Nicholson.

"When air masses are forced over mountains and downslope, they warm and their capacity for holding water vapor increases," wrote Susan Woodward, an emeritus geography professor at Virginia's Radford University, on a website about deserts. On the leeward side of a mountain, she added, evaporation happens faster than rainfall, creating an arid environment.

Kalahari Desert

360,000 square miles (930,000 square km)

The Kalahari Desert covers large tracts of South Africa, Botswana and Namibia. It averages less than 20 inches (500 mm) of rain a year in, but some locations receive less than 8 inches (200 mm) annually, according to the 1991 book The Kalahari Environment by David G. Thomas and Paul A. Shaw.

Described as "featureless" by the Encyclopedia Britannica, the Kalahari is mostly covered by sand sheets that were formed sometime between 2.6 million and 11,700 years ago, probably due to the action of wind and rain. The sheets have been virtually unchanged since then.

The Kalahari was also a site of human activity thousands of years ago. In one excavated area, South Africa's Wonderwerk Cave, archaeologists found evidence of fires lit about one million years ago. A separate discovery of artifacts in Botswana's Tsodilo Hills implied humans performed rituals 70,000 years ago.

Gobi Desert

800,000 square miles (1.3 million square km)

Encompassing large regions of China and Mongolia, the Gobi Desert is arid in parts and more "monsoon-like" in others, meaning it sees wet and dry seasons, according to the Encyclopedia Britannica. Rainfall varies from about 2 to 8 inches a year (50 mm to 200 mm), depending on the location. The eastern region in particular gets a lot of rainfall in the summer, similar to how monsoons operate in wetter regions.

In 2011, strange zigzag patterns in the Gobi emerged in Google's pictures, prompting a range of conspiracy theories that even included aliens. But the lines were most likely used to calibrate Chinese spy satellites to help the spacecraft orient themselves in orbit, said Jonathon Hill, a research technician and mission planner at the Mars Space Flight Facility at Arizona State University.

The Gobi is also a good spot for dinosaur-hunting. A rare Tyrannosaurus Rex skeleton uncovered in that region was auctioned off in 2012, fetching $1 million amid a legal dispute.

Arabian Desert

900,000 square miles (2.3 million square km)

The Arabian Desert encompasses Saudi Arabia and surrounding countries such as Oman and parts of Iraq. How dry and hot the desert is depends on where you're standing. The interior of the desert can get to a scorching, dry 129 F (54 C). Areas on the coast and in the highlands, however, have more humidity and can also have fog and dew during the cooler parts of the day, according to the Encyclopedia Britannica.

On average, annual rainfall is less than 4 inches (100 mm), but depending on the region it can range anywhere from 0 to 20 inches (0 to 500 mm). But human activity has artificially irrigated and greened parts of the desert.

Crop circles exploded in abundance in Saudi Arabia during the past three decades, according to a series of Landsat images. These are possible because engineers drilled into a "fossil" water acquifer that is more than 20,000 years old, according to NASA. It has been estimated that at current rates of usage, the water will go dry in 50 years.

Sahara

3.3 million square miles (8.6 million square km)

The Sahara is notable not only for its vast size, but parching lack of rainfall. Annual precipitation in the world's second-largest desert is less than 0.9 inches (25 mm) every year. On the east side of the desert, according to NASA, rainfall could be as low as 0.2 inches (5 mm) annually.

While water doesn't often fall to the ground, it's common for water droplets to hover above the desert as fog. There isn't much vegetation in the Sahara to hold on to heat after the sun goes down, so the temperatures can actually get quite cold at night. The sudden shift between day and night temperatures can bring about the fog.

The desert also features a high volcano, Emi Koussi, which is in Chad at the southeastern end of the Tibesti Range. Standing 11,204 feet (3,415 meters) above sea level, there are lava flows and other volcanic features that appear to be as young as two million years old. There is also an active thermal region on the volcano's south flank.

Antarctica

5.5 million square miles (14.2 million square km)

Nestled around the South Pole, where the coldest temperature on Earth was recorded and which doesn't receive sunlight for months every year, it's sometimes hard to think of icy Antarctica as a desert. But it is the world's largest one because very little precipitation falls there — on average, it gets less than 2 inches (50 millimeters) a year, mostly as snow.

Despite the low snowfall, vast glaciers cover 99 percent of Antarctica's surface. That's because the average temperature (minus 54 degrees Fahrenheit, or minus 48 degrees Celsius) slows down evaporation to a crawl. Over long periods of time, the snowfall accumulates at a rate faster than Antarctica's ablation, according to "Discovering Antarctica," a project of the U.K.'s Royal Geographical Society.

Parts of Antarctica are showing strong signs of warming up along with global climate change, however. Temperatures in the Antarctic Peninsula have increased by 4.5 degrees Fahrenheit (2.5 degrees Celsius) over the past 50 years — five times the rate of the rest of the planet. And scientists think that warm ocean waters could be melting Antarctica's glaciers as they flow under the floating tongues of ice.

The link between drought and the rise and fall of Egypt's ancient cultures, including the pyramid builders, has long fascinated scientists and historians. Now, they're looking into an unexpected source to find connections: mummy teeth.

A chemical analysis of teeth enamel from Egyptian mummies reveals the Nile Valley grew increasingly arid from 5,500 to 1,500 B.C., the period including the growth and flourishing of ancient Egyptian civilization.

"Egyptian civilization was remarkable in its long-term stability despite a strong environmental pressure — increasing aridity — that most likely put constraints on the development of resources linked to agriculture and cattle breeding," said senior study author Christophe Lecuyer, a geochemist at the University of Lyon in France.

Many studies have linked dramatic droughts to crises near the end of the Old Kingdom (the Age of the Pyramids) in the third millennium B.C. But Lecuyer and his colleagues also found a jump in aridity before the downfall of Egypt in the 6th century B.C. during the Late Period, when it was conquered by Alexander the Great.

However, the new study can't resolve the occasional drops in annual Nile River floods or short-term droughts that often caused widespread famine and upsets in Egyptian history. [Gallery: Amazing Egyptian Discoveries]

"Our database cannot identify short-term events, only long-term trends, and there is [only] one obvious major event of increasing aridity that took place before the Late Period," Lecuyer said.

The climate data comes from the teeth of Egyptian mummies from various dynasties at the Musée des Confluences de Lyon in France. Led by graduate student Alexandra Touzeau,the researchers drilled small amounts of enamel off some of the teeth and tested it for oxygen and strontium isotopes.

The mummy's teeth record the ratio of two oxygen isotopes (oxygen atoms with different numbers of neutrons) in their diet and their drinking water, which in this case is Nile River water, Lecuyer said. Shifts in the ratio of the isotopes indicate changing precipitation patterns in the region.

The isotopes can also indicate what people were eating, and the research team plans to publish additional studies of Egyptian diets through time, Lecuyer said. "The general drying trend had no negative impact on the Egyptian civilization in terms of cereal production or population," he said. "One of the studies we plan to publish soon reveals there was no diet change over this long period of about four millennia."

The Nile Valley wasn't the only part of North Africa to experience drying after 5,500 B.C. The Sahara Desert was once covered in lakes and grasslands, but switched to a drier regime between about 7,000 to 5,000 years ago, studies have shown.

The mummy teeth findings were published June 2 in the journal Earth and Planetary Science Letters.

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

From lakes and grasslands with hippos and giraffes to a vast desert, North Africa's sudden geographical transformation 5,000 years ago was one of the planet's most dramatic climate shifts.

The transformation took place nearly simultaneously across the continent's northern half, a new study finds. The results will appear in an upcoming issue of the journal Earth and Planetary Science Letters.

The findings come from analyses of dust blown west from Africa and dropped into the Atlantic Ocean. Researchers sifted through 30,000 years of dust and ocean bottom muck retrieved with ocean drilling ships. The changing levels of windblown dust in the ocean sediments provide scientists with clues to Africa's climate and how it has changed over time. Simply put, a lot of dust means drier conditions and less dust means a wetter environment.

The wet period, called the African Humid Period, started and ended suddenly, confirming previous studies by other groups, the sediments revealed. However, toward the Humid Period's end about 6,000 years ago, the dust was at about 20 percent of today's level, far less dusty than previous estimates, the study found.

The study may give scientists a better understanding of how changing dust levels relate to climate by providing inputs for climate models, David McGee, an MIT paleoclimatologist and lead study author, said in a statement. Sahara desert dust dominates modern-day ocean sediments off the African coast, and it can travel in the atmosphere all the way to North America.

McGee and his colleagues are now testing whether the dust measurements can resolve a long-standing problem: the inability of climate models to reproduce the magnitude of wet conditions in North Africa 6,000 years ago.

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanet, Facebook or Google+. Original article on LiveScience's OurAmazingPlanet.

Archaeologists have uncovered 20 Stone-Age skeletons in and around a rock shelter in Libya's Sahara desert, according to a new study.

The skeletons date between 8,000 and 4,200 years ago, meaning the burial place was used for millennia.

"It must have been a place of memory," said study co-author Mary Anne Tafuri, an archaeologist at the University of Cambridge. "People throughout time have kept it, and they have buried their people, over and over, generation after generation."

About 15 women and children were buried in the rock shelter, while five men and juveniles were buried under giant stone heaps called tumuli outside the shelter during a later period, when the region turned to desert.

The findings, which are detailed in the March issue of the Journal of Anthropological Archaeology, suggest the culture changed with the climate.

Millennia of burials

From about 8,000 to 6,000 years ago, the Sahara desert region, called Wadi Takarkori, was filled with scrubby vegetation and seasonal green patches. Stunning rock art depicts ancient herding animals, such as cows, which require much more water to graze than the current environment could support, Tafuri said. 

Tafuri and her colleague Savino di Lernia began excavating the archaeological site between 2003 and 2006. At the same site, archaeologists also uncovered huts, animal bones and pots with traces of the earliest fermented dairy products in Africa. [See Images of the Stone-Age Skeletons]

To date the skeletons, Tafuri measured the remains for concentrations of isotopes, or molecules of the same element with different weights.

The team concluded that the skeletons were buried over four millennia, with most of the remains in the rock shelter buried between 7,300 and 5,600 years ago.

The males and juveniles under the stone heaps were buried starting 4,500 years ago, when the region became more arid. Rock art confirms the dry up, as the cave paintings began to depict goats, which need much less water to graze than cows, Tafuri said.

The ancient people also grew up not far from the area where they were buried, based on a comparison of isotopes in tooth enamel, which forms early in childhood, with elements in the nearby environment.

Shift in culture?

The findings suggest the burial place was used for millennia by the same group of people. It also revealed a divided society.

"The exclusive use of the rock shelter for female and sub-adult burials points to a persistent division based on gender," wrote Marina Gallinaro, a researcher in African studies at Sapienza University of Rome, who was not involved in the study, in an email to LiveScience.

One possibility is that during the earlier period, women had a more critical role in the society, and families may have even traced their descent through the female line. But once the Sahara began its inexorable expansion into the region about 5,000 years ago, the culture shifted and men's prominence may have risen as a result, Gallinaro wrote.

The region as a whole is full of hundreds of sites yet to be excavated, said Luigi Boitani, a biologist at Sapienza University of Rome, who has worked on archaeological sites in the region but was not involved in the study.

"The area is an untapped treasure," Boitani said.

The new discovery also highlights the need to protect the fragile region, which has been closed to archaeologists since the revolution that ousted dictator Moammar el Gadhafi.

Takarkori is very close to the main road that leads from Libya into neighboring Niger, so rebels and other notorious political figures, such as Gadhafi's sons, have frequently passed through the area to escape the country, he said.

Follow Tia Ghose on Twitter @tiaghose. Follow LiveScience on Twitter @livescience. We're also on Facebook &Google+. Original article on LiveScience.com

An arid landscape

Archaeologists have found hundreds of relics of Stone Age culture in Wadi Takarkori, a dried up riverbed in Southwest Libya's Sahara desert

Sand Dunes

Nowadays, the region is part of the great Sahara Desert, but stunning rock art from 8,000 to 6,000 years ago reveals that the region was once wet enough to graze cows, a water-intensive proposition

Wetter history

At that time, the region looked more like Mali, with scrubby plants and seasonal vegetation that quickly greened with the rains.

Stone Age Skeletons

While excavating in the region, which has hundreds of rock art sites, Mary Anne Tafuri and her colleague Savino di Lernia uncovered a Stone Age burial in a rock shelter with skeletons of women and children that belonged to an ancient herding culture.

Women's Site

The skeletons were mainly buried between 7,300 and 5,600 years ago, when the region was wetter and cow herding was common. The presence of women only suggested that women played a critical role in the society, which may have even traced family descent through the maternal line.

Shift in Culture

But once the Sahara Desert began its inexorable expansion into the region, herders shifted to less water-hungry animals such as goats, and the burial practices changed. Women were no longer buried in the cave and starting around 4,500 years ago, men and juveniles were buried under great stone heaps called tumuli outside the rock shelter, perhaps reflecting men's increased cultural importance.

Winds are blowing massive clouds of Saharan dust over the Atlantic Ocean, as shown in this image captured today (Oct. 8) by NASA's Aqua satellite.

Plumes of dust extend from the Western Sahara and Mauritania to the west of the Cape Verde islands . This is the second day winds have whipped up dust storms in the region.

Seas of sand sprawl across Mauritania and the neighboring Sahara desert and Sahel region. The Saharan Air Layer — an arid, dust-laden air mass that forms over the Sahara between late spring and early fall — frequently transports dust westward across the Atlantic Ocean, where hurricanes form. Some of the dust even makes it as far north and west as Bermuda, whose red soils hail from the Sahara.

Many scientists used to think that these clouds of dust helped form hurricanes, but now that conclusion is up in the air; some evidence shows dust storms hinder hurricane formation.

The area surrounding the Cape Verde islands is known to spawn hurricanes, most commonly in August and September. In rare years, such as 1995, a Cape Verde-type hurricane will form in late July or early October, according to the National Hurricane Center.

Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

Bermuda is known for its white sand beaches and its stunning red soils, called "terra rossa." But the origin of this red earth has been a bone of contention among geologists. How did it get there?

A new study suggests that much of it blew in all the way from Africa, accumulating little by little over the last 1 million years or so. In the study, published Sept. 1 in the Journal of Geophysical Research, scientists found that the chemical makeup of Bermuda's red soils closely matched that of clay-rich dust blown out of Africa.

The dust comes from the Sahara and the Sahel regions of northern Africa. It's blown to Bermuda by westerly winds, a process enhanced by hurricanes and tropical storms. Some research has suggested that this dust can actually disrupt hurricane formation, though scientists are still studying this potential effect.

The origin of Bermuda's clay-filled, iron-rich soils has been something of a mystery, since the white sand dunes and beaches of the island don't contain the minerals necessary for forming red earth, said co-author Daniel Muhs, a researcher at the U.S. Geological Survey. Bermuda's white sands are made of calcium carbonate and derived from eons-old corals and shellfish, Muhs told OurAmazingPlanet.

That left two possible origins for terra rossa: Either it formed from the breakdown of volcanic rock buried beneath sand dunes, or it blew in from elsewhere, likely Africa.

The study found, for the first time, that wind carrying African dust did make it as far north as Bermuda, which is at the same latitude as South Carolina. It also found that some of Bermuda's red soil is formed from the breakdown of volcanic rocks, but that this doesn't account for all of the island's earth.  

Over time, this yearly peppering of dust has enriched soils in Florida, Bermuda and elsewhere in the Caribbean, without which the soil in these areas would be much poorer.

"There aren't many plants that can grow in calcium carbonate," Muhs said. "For plants to grow, you need clays, which are reservoirs of soil nutrients, in this case blown in by the wind."  

Reach Douglas Main at dmain@techmedianetwork.com. Follow him on Twitter @Douglas_Main. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

Aerial eruption

On Aug. 15, NASA's Earth Observing-1 (EO-1) satellite caught a crystal-clear image of a small ash plume emanating from a tiny volcanic Indonesian island.

The volcano, called Batu Tara, is located on the island of Pulau Komba, and has been experiencing frequent, mild eruptions since mid-2006, according to a NASA release.

[Full Story: Photo: Overhead View of a Volcano Eruption]

Fly away free

Seven of California's endangered light-footed clapper rails that were bred by the San Diego Zoo were released into the wild this week. The marsh birds added to a banner year for the species.

The seven birds were hatched at the San Diego Zoo Safari Park and Living Coast Discovery Center. They were released at the 915-acre San Elijo Lagoon Ecological Reserve on Aug. 16.

[Full Story: Photo: Endangered Birds Released Into Wild]

Ready, aim, rain again

Typhoon Kai-tak, which strengthened from its former tropical storm status, was spotted by a NASA satellite today (Aug. 16) as it prepares to make landfall along the China-Vietnam border.

The typhoon is currently about 155 nautical miles south of Hong Kong and is moving to the west-northwest, which is expected to take it over China's Leizhou Bandao peninsula and northern Vietnam on Aug. 17 and 18, according to the U.S. Joint Typhoon Warning Center (JTWC).

[Full Story: Typhoon Takes Aim at China, Vietnam]

Saharan dust

Astronauts sailing around the Earth aboard the International Space Station recently spotted a dull haze blanketing the skies over the Caribbean dust from Africa's vast Sahara Desert that had blown all the way across the Atlantic Ocean.

The dust likely originated some 5,000 miles (8,000 kilometers) to the east, in the dry reaches of northern Mali, according to NASA figures, although some satellite data suggest the dust can come from as far east as Chad or Sudan.

[Full Story: Astronaut Photo: Sahara Dust Enters Caribbean Skies]

What's up, doc?

A ghost shark. In the place of teeth, the fish have wide bony plates, lending them a goofy mouth shape that resembles that of a bucktoothed rabbit.

[See More: Images: Weird Deep-Sea Sharks]

Batterd by wind

NASA's Terra satellite passed over Tropical Storm Gordon, the most recently formed storm of the 2012 Atlantic hurricane season, yesterday (Aug. 16) and saw that atmospheric wind patterns were battering the storm.

Gordon intensified into a tropical storm early yesterday morning and has strengthened since then. The latest update from the U.S. National Hurricane Center (NHC) put Gordon's maximum sustained winds at 65 mph (100 kph).

[Full Story: Satellite Spies Tropical Storm Gordon]

Astronauts sailing around the Earth aboard the International Space Station recently spotted a dull haze blanketing the skies over the Caribbean — dust from Africa's vast Sahara Desert that had blown all the way across the Atlantic Ocean.

The dust likely originated some 5,000 miles (8,000 kilometers) to the east, in the dry reaches of northern Mali, according to NASA figures, although some satellite data suggest the dust can come from as far east as Chad or Sudan.

In the photograph, captured in July 2012, the Saharan dust covers the skies over the island of Hispaniola — home to Haiti and the Dominican Republic — and the Turks and Caicos Islands, yet Cuba's skies are dust-free.

It takes about a week for the dust to travel from Africa's deserts to the Caribbean, and in recent years, researchers have learned that dust from the Sahara travels across the ocean and reaches the Western Hemisphere during every month of the year.

The traveling dust has been linked to some troubling phenomena, from coral disease to allergies in humans to dangerous algae blooms known as red tides.

Dust blown in from Africa may also play a role in hurricane formation. Some researchers suspect the high-flying dry dust can break up the rotating storms, but others say more data are needed before reaching such conclusions.

Follow OurAmazingPlanet for the latest in Earth science and exploration news on Twitter @OAPlanet. We're also on Facebook & Google+. 

This article was provided by AccuWeather.com.

A very concentrated area of Saharan Dust has traveled all the way from Africa and is now heading toward Florida.

The northern Caribbean islands have already been dealing with Saharan dust with very hazy skies.

"This is the largest concentration of dust that I have seen making it that far west across the Atlantic this year," AccuWeather Expert Senior Meteorologist Bernie Rayno said. "Usually dust starts to dissipate as it reaches the western Atlantic."

A webcam image from the south shore of St. John in the Virgin Islands at 9:15 a.m. on Tuesday, July 17, 2012, (to the left) shows hazy, dusty skies. At this time, they were located on the eastern edge of the dust. The image to the right was the same webcam around 3:00 p.m. on Tuesday. The dust had moved on to the west.

Saharan dust is a limiting factor for tropical development in the Atlantic and also causes nasty hazy skies when it is so densely concentrated. However, sunsets are stunning as a result of dust clouds high in the sky with notable, bright red colors on display.

Origin of the Dust The Sahara is the greatest single stretch of desert in the world, besides the Arctic and Antarctic, stretching about 3.5 million square miles across northern Africa.

Rainfall is rare across much of the Sahara, and sparing across the rest of the desert.

"Persistent high pressure with resultant sinking and drying of air is what tends to limit rainfall across the region. There is likely a 'feedback' mechanism at work by which dry, sparsely vegetated earth superheats, thereby further warming the atmosphere and further strengthening the area of high pressure," AccuWeather Expert Senior Meteorologist Jim Andrews explained.

Persistent northeasterly winds, squeezed between an area of high pressure over the northern Sahara and low pressure over the equator, are often strong enough to stir loose sand and dust in the Sahara. Although the coarser sand is not normally raised far above the land, the smaller dust particles can be lofted 2 or 3 miles high into the sky, Andrews said.

Especially strong winds can blow over thousands of square miles of the desert can scour enormous volumes of dust from the surface. According to a University of Wisconsin-Madison study by Amato Evan, the amount of dust is said to be in the millions of tons.

A large, swirling mass of dust, visible on the left portion of this MODIS satellite image, is seen blowing from the Western Sahara into the Atlantic Ocean on Sept. 4, 2005. Image from NASA.

During a dust storm in the Sahara, which can last for days, the visibility can drop to zero. These long dust storms yield clouds of dust that span one thousand miles or more. Large dust clouds can traverse westward across the Atlantic as they get steered by trade winds.

"Under favorable settings, dust aloft can reach customary tropical cyclone breeding areas, including "Hurricane Alley", which stretches eastward from the Lesser Antilles," Andrews said.

Impacts of the Dust The clouds of dust are associated with large zones of dry air, which is an inhibiting factor for tropical storms and hurricanes.

The large zone of dust and dry air has been one of the factors in the recent quiet state of the tropics in the Atlantic.

Beautiful sunsets are observed since the Saharan dust clouds resides so high in the atmosphere. The dust particles act to scatter certain wavelengths of light, allowing red hues to be illuminated.

Yet another large cloud of dust has recently moved off the western coast of Africa and appears like it will continue to move westward across the Atlantic.

Content was contributed by Expert Senior Meteorologist Jim Andrews.

© AccuWeather.com. All rights reserved. More from AccuWeather.com.

Intro

Bored with road races? Think you've done it all? Channel your inner Roald Amundsen the Norwegian explorer that won the race to the South Pole 100 years ago and sail to Antarctica. Here you'll find one of the most challenging races on the planet The Last Desert Race.

Yes, Antarctica is a frozen desert. Just a few inches of rain and snow falls here each year. It is also the highest, windiest and coldest continent on Earth, with a huge plateau covered by an enormous ice sheet.

But before you can experience the terrain firsthand, you'll have to complete three other desert challenges. We've got the details on these races plus two more runs across some of the world's harshest deserts.

Atacama Crossing Chile

To qualify for the Antarctica race, you must conquer three other grueling desert races.

The Atacama Crossing race in Chile is first in the "4 Deserts" series, which was ranked second on TIME magazine's list of Top 10 Endurance Competitions in the world.

The Atacama Desert is one of the driest places on Earth and is the most lunar-like landscape on Earth. NASA tests its Moon rovers here. The Atacama Desert is 15 million years old and 50 times more arid than California's Death Valley. Keep your head on a swivel here: Some of the oldest mummies found on Earth come from the Atacama Desert, dating as far back as 7,000 years.

The race's elevation varies, but the entire race is held at least 1.4 miles (2.3 kilometers) above sea level and peaks at 10,000 feet (3,000 meters) above sea level. The race spans 150 miles (250 km), which is far enough to cross the width of Chile. Temperatures during the day are around 104 degrees Fahrenheit (40 degrees Celsius). At night, temperatures may drop to 41 degrees Fahrenheit (5 degrees Celsius).

Gobi March China

Next in the "4 Deserts" series is the Gobi March in China. Kashgar is the host city for the 155-mile (250-km), 7-day, 6-stage foot race. Along the course, runners will pass Shipton's Arch (Heaven's Gate to locals), which is a natural arch that is taller than the Empire State Building.

In the Gobi Desert, runners trek across dry, rocky riverbeds, dusty tracks, narrow ridge paths and green pastures. Average temperatures are between 95 to 113 F (35 to 45 C).

Twenty percent of competitors run the entire course; others split time running and walking. A few walk the entire course. This year's fastest completion time is expected to be around 24 hours and the slowest around 70 hours.

Sahara Race Egypt

The iconic Sahara Desert, the largest non-polar desert in the world, is home to the third race in the "4 Deserts" series. This race is also 155-miles (250-km) long, but it's run across the hottest desert in the world.

During the event, competitors cross through The Valley of the Whales, where an ancient shallow sea once covered the land. Competitors pass fossils that are believed to be from whales with legs that died out 40 million years ago. The 2012 course will finish at the Pyramids of Giza.

The terrain is a mixture of hard-packed sand, soft sand and sand dunes. Temperatures on the course reach as high as 122 F (50 C). Bring plenty of water.

Up to 200 competitors from more than 40 countries are expected to compete in the Sahara Race 2012. The fastest completion time is expected to be around 26 hours and the slowest around 70 hours.

Badwater Ultramarathon

Now that you've qualified for Antarctica, here are two more of the world's most extreme desert races for your bucket list.

The Badwater Ultramarathon is billed as the world's toughest footrace. This 135-mile (217-km) course begins at 282 feet (86 m) below sea level in California's Death Valley. The course then climbs to 8,360 feet (2,548 m) at Whitney Portal, the trailhead to Mount Whitney.

The race is held every year in mid-July, when the weather conditions are most extreme and temperatures over 120 F (49 C), even in the shade, are not uncommon. Few people finish the race.

Siberian Ice "Marathon"

To prepare for racing across Antarctica, try this icy race, dubbed the "Coldest Marathon." This race isn't really a marathon at all. It is technically a half marathon, but with temperatures far below freezing, runners will feel like they're covered twice as much ground.

The Siberia Ice Marathon takes place in Omsk, Siberia (where the writer Fyodor Dostoyevsky was exiled). During the race, organizers hand out hot tea instead of water.

During the coldest of these races, held in January 2001, the air temperature averaged minus 39 degrees Fahrenheit (3.9 degrees Celsius), and it got as low as minus 44 F (minus 42 C). Of the 134 people who started the race, 11 finished.

To put that day in perspective, anyone who started that race only had an eight percent chance of finishing it, about as low as the current freshman acceptance rate at Harvard University.

The Last Race Antarctica

So you've trudged across the Atacama, trekked the Gobi and slogged through the Sahara. Your reward is The Last Desert race the only multi-day stage race on the Antarctic continent.

The starting point isn't in Antarctica, but in Ushuaia, Argentina. Competitors will board the expedition ship, the Antarctic Dream, to sail across the Drake Passage to several locations in Antarctica. [Images: Above Antarctica's Icy Wilderness]

The terrain will be largely snow and it varies in depth from just a few inches to several feet. Temperatures on the course can reach as low as minus 4 F (minus 20 C). A bath in thermal waters on Deception Island is like a dip in the spa for these racers.

Finish all four of the 4 Desert races in one calendar year and you'll be one of the few to finish the 4 Deserts Grand Slam. Then you'll really have done it all. [Read more: 9 Stunning Scenic Races]

New evidence of a lost civilization in an area of the Sahara in Libya has emerged from images taken by satellites.

Using satellites and air photographs to identify the remains in one of the most inhospitable parts of the desert, a team from the University of Leicester in England has discovered more than 100 fortified farms and villages with castle-like structures and several towns, most dating between AD 1 to 500.

"It is like someone coming to England and suddenly discovering all the medieval castles. These settlements had been unremarked and unrecorded under the Gadhafi regime," said project leader David Mattingly, professor of Roman archaeology at the university. The fall of the regime has opened up Libya to more exploration by archaeologists of its pre-Islamic heritage.

These "lost cities" were built by a little-known ancient civilization called the Garamantes, whose lifestyle and culture was far more advanced and historically significant than ancient sources had suggested. [Related: History's Most Overlooked Mysteries]

Castle-like complexes

The team from the University of Leicester has identified the mud brick remains of the castle-like complexes, with walls still standing up to 13 feet (4 meters) high, along with traces of dwellings, cairn cemeteries, associated field systems, wells and sophisticated irrigation systems. Follow-up ground surveys earlier this year confirmed the pre-Islamic date and remarkable preservation of the sites.

"Satellite imagery has given us the ability to cover a large region. The evidence suggests that the climate has not changed over the years and we can see that this inhospitable landscape with zero rainfall was once very densely built up and cultivated. These are quite exceptional ancient landscapes, both in terms of the range of features and the quality of preservation," said Martin Sterry, who has been responsible for much of the image analysis and site interpretation.

The findings challenge a view dating back to Roman accounts that the Garamantes consisted of barbaric nomads and troublemakers on the edge of the Roman Empire.

"In fact, they were highly civilized, living in large-scale fortified settlements, predominantly as oasis farmers. It was an organized state with towns and villages, a written language and state of the art technologies. The Garamantes were pioneers in establishing oases and opening up trans-Saharan trade," Mattingly said.

Libyan heritage

The professor and his team were forced to evacuate Libya in February when the anti-Gadhafi revolt started, but hope to be able to return to the field as soon as security is fully restored. The Libyan antiquities department, badly neglected under Gadhafi, is closely involved in the project.

"It is a new start for Libya's antiquities service and a chance for the Libyan people to engage with their own long-suppressed history," Mattingly said. "These represent the first towns in Libya that weren't the colonial imposition of Mediterranean people such as the Greeks and Romans. The Garamantes should be central to what Libyan school children learn about their history and heritage."

The research is funded by the European Research Council, the Leverhulme Trust, the Society for Libyan Studies and the GeoEye Foundation.

This story was provided by OurAmazingPlanet, a sister site to LiveScience.

Snakebites are a significant public health problem in sub-Saharan Africa, yet the problem is neglected, researchers say. As many as 1.5 million people in that region are bitten by snakes each year, according to a new study that analyzed three decades worth of surveys and medical reports. Previous studies were based on less reliable methods and may have underestimated the problem, the researchers said. The majority of snakebites and deaths from these bites occur in rural areas, where access to health care services is limited, the researchers said. The new findings are important because, without knowing the true size of the problem, and which areas are most affected, authorities cannot properly address the issue, said study researcher Jean-Philippe Chippaux, of the Institute of Research for Development (IRD) in Paris. Currently there is only enough anti-venom (also called antivenin) available in the region to treat about 10 percent of snakebite cases. Pharmaceutical companies have been reluctant to manufacture anti-venom because they do not know how much to make or where to distribute it, Chippaux said. The new findings may signal to these companies that there is a need for more anti-venom. Doctors in the region should also be trained to treat snake bites and administer anti-venom, Chippaux said. Deadly snake bites Some people are bitten by nonvenomous snakes and others by venomous snakes that don't inject venom. All told, about half of snake bites actually result in venom being injected into the victim. However, complications from these bites can severe or fatal. For instance, the ocellated carpet viper is common in the African savannahs, and has very potent venom that can cause hemorrhaging. Without treatment, up to 20 percent of victims will die and 5 percent will require amputations, Chippaux said. Bites from cobras and mambas can also be deadly, because their venoms can cause paralysis of the muscles needed to breathe, leading to death from lack of oxygen within six hours. Chippaux and colleagues reviewed about 100 articles and clinical reports published between 1970 and 2010. They found about 314,000 cases of poisonous snake bites are reported to health care systems each year. However, many cases go unreported because people do not have easy access to health care centers, and may go to a traditional healer instead, so the researchers also looked at household surveys. They found the actual number of snakebites may be three to five times higher, or between 900,000 and 1.5 million. About 95 percent of bites occurred in rural areas, such as on plantations. Agricultural workers are therefore particularly at risk for bites, the study said. Reports from health care systems show that bites kill about 7,300 people and cause between 6,000 and 14,600 amputations each year, but based on the household surveys, the researchers said the actual numbers may be closer to 20,000 to 25,000 deaths and 30,000 amputations. More antivenom doses The number of doses of anti-venom available in Africa has dropped dramatically since the 1980s, from about 200,000 to less than 20,000. The new analysis indicated about 500,000 doses are needed each year. Chippaux said he hopes the new findings will convince political, economical and health authorities to pay attention to the problem, and understand that it is not impossible to fix. "Now we know the problem — we have solutions," Chippaux said.  The researchers announced their findings on Friday (Sept. 9); the study was published in the March issue of the journal Toxicon. Pass it on: Snakebites cause significant morbidity and mortality in sub-Saharan Africa, yet only 10 percent of victims are treated.

This story was provided by MyHealthNewsDaily, a sister site to LiveScience. Follow MyHealthNewsDaily staff writer Rachael Rettner on Twitter @RachaelRettner. Find us on Facebook.

Fish may have once swum across the Sahara, a finding that could shed light on how humanity made its way out of Africa, researchers said.

The cradle of humanity lies south of the Sahara, which begs the question as to how our species made its way past it. The Sahara is the largest hot desert in the world, and would seem a major barrier for any humans striving to migrate off the continent.

Scientists have often focused on the Nile Valley as the corridor by which humans left Africa. However, considerable research efforts have failed to uncover evidence for its consistent use by people leaving the continent, and precisely how watery it has been over time is controversial.

Now it turns out the Sahara might not have been quite as impassable as once thought — not only for humanity, but for fish as well.

"Fish appeared to have swam across the Sahara during its last wet phase sometime between 10,000 and 6,000 years ago," researcher Nick Drake, a geographer at King's College London, told LiveScience. "The Sahara is not a barrier to the migrations of animals and people. Thus it is possible — likely? —that early modern humans did so, and this could explain how we got out of Africa."

Using satellite imagery and digital maps of the landscape, the researchers found the Sahara was once covered by a dense network of rivers, lakes and inland deltas. This large waterway channeled water and animals into and across the Sahara during wet, "green" times.

In their analysis, Drake and his colleagues found evidence that many creatures, including aquatic ones, dispersed across the Sahara recently. For example, 25 North African animal species have populations both north and south of the Sahara with small refuges within the desert, including catfish (Clarias gariepinus), tilapia (Tilapia zillii), jewel cichlid fish (Hemichromis letourneuxi) and freshwater snails such as the red-rimmed melania (Melanoides tuberculata). Indeed, more animals may have once crossed over the Sahara than over the Nile corridor, the researchers said — only nine animal species that occupy the Nile corridor today are also found both north and south of the Sahara.

If fish could have crossed the Sahara, it is hard to imagine that humans didn't. Analysis of African languages and artifacts suggest that ancient waterways recently affected how humans occupied the Sahara. For instance, speakers of Nilo-Saharan languages once lived across central and southern Sahara, and may have once hunted aquatic creatures with barbed bone points and fish hooks. In addition, ancient lake sediments suggest the Sahara was green roughly 125,000 years ago, back when anatomically modern humans might have begun migrating out of Africa.

Future work could focus on when species got across the Sahara — genetic analysis of fish could help pinpoint such times in fish, Drake said. However, further research into the past of the Sahara could prove difficult and even dangerous, he noted. Some of the Saharan countries the researchers would like to visit in order to analyze the genetics of fish populations or date the ages of ancient shorelines "are deemed to be too dangerous to visit due to terrorist activity or civil war," Drake said.

The scientists detailed their findings online Dec. 27 in the journal Proceedings of the National Academy of Sciences.

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The red tint of the soil of certain Mediterranean regions, including Mallorca and Sardinia, comes from dust blown in from Africa, a new study finds.

Spanish and American researchers have conducted a mineralogical and chemical analysis to ascertain the origin of the red soil, or "terra rossa," in the Mediterranean. The results of the study reveal that mineral dust from the Sahara and Sahel region of Africa, which emit between 600 and 700 tons of dust a year, brought about the reddish soil between 12,000 and 25,000 years ago.

"The first hint of the relationship between African dust and certain soils in the region of the Mediterranean is their reddish or reddish-brown color, similar to that of African aerosol filters, caused by their clay content," said study co-author Anna Ávila, of the Centre for Ecological Research and Forestry Applications (CREAF) at the Universidad Autónoma de Barcelona.

The study, detailed in the journal Quaternary Science Reviews, found that African mineral dust additions "play an important role" in the origin of the soils (palaeosols) in the Mediterranean region , namely on the island of Mallorca. Past studies have found similar results for soils on Sardinia, "which indicates the likelihood of Africa being a common source," the researchers said.

"Terra rossa" (red soil in Italian) is located on carbonate rock (with a high content of carbonate) and is spread throughout the Iberian Peninsula, the South of France, the islands in the Mediterranean, Italy and along the coast of the Adriatic Sea, from Slovenia to Greece.

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Most people spend their lives trying to avoid dust or get rid of it, but researchers from the University of Alabama in Huntsville are planning to spend the next three years pursuing 770 million tons of dust carried from the Sahara into the atmosphere annually and trying to determine its impact on our climate.

Some of the dust from the world's largest desert falls back to earth before it leaves North Africa. Some of it blows out over the Atlantic Ocean, carried by wind to South America and the United States, or over the Mediterranean Sea.

Wherever the dust goes, these scientists will be using data from several research satellites to assess its effect on the planet.

"The people who build climate models make some assumptions about dust and its impact on the climate," said Sundar Christopher, an Alabama in Huntsville professor of atmospheric science. "We want to learn more about the characteristics of this dust, its concentrations in the atmosphere and its impact on the global energy budget so we can replace those assumptions with real data."

A dust particle measures about 10 microns across, or about one-tenth the width of a human hair. Their particular size gives particles the ability to absorb some solar radiation. That radiation heats up the particle, which then radiates the heat into the air.

Dust particles can also cool the atmosphere by reflecting some incoming solar radiation back into space. To add further to its effects, dust absorbs thermal energy rising from the ground and re-radiates it either toward space or back toward Earth's surface.

"One thing we want to do is calculate how reflective dust is, because not all dust is created equal," Christopher said. "We're trying to calculate reflectivity so we can say with precision how much sunlight is being reflected."

Dust from the Sahara was chosen because that vast desert it covers about 3.5 million square miles (9.1 million square kilometers) contributes about half of the dust carried into the atmosphere every year, and Christopher said the dust is more "pristine" than dust from U.S. or Asian deserts, which often contains pollutants.

The composition and shape of dust particles are complex, and the composition varies depending on which part of the Sahara it comes from. Some absorbs more solar energy than others.

Studying the Saharan dust is also a challenge because the dust in the atmosphere looks very much like the surface below it. Only in the past few years have new instruments and techniques been developed that help scientists detect which is dust and which is desert.

Christopher has received a grant of almost $500,000 through NASA's Calipso program ("Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation") to support the research for the next three years.

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