A small, soft space rock smacked into Costa Rica on April 23, 2019. And it may have carried building blocks for life.
The washing machine-sized clay fireball broke up before landing, . Locals found shards scattered between two villages, La Palmera and Aguas Zarcas. And while meteorites turn up all over Earth, these shards were special; the asteroid that spawned them was a soft remnant of the early solar system, made from the dust from the spinning nebula that would ultimately form our solar system, formed in even older stars. And the meteorites that rained down from the event — collectively called Aguas Zarcas — belong to a rare class called carbonaceous chondrites, which form in the wee hours of the solar system's emergence and are typically packed with carbon. This particular space rock contains complex carbon compounds, likely including amino acids (which join to form proteins and DNA) and perhaps other, even more complex building blocks of life.
Related: How did life arise on Earth?
While other rocky chunks from the very early solar system became parts of planets, this one remained intact and changed over time only through sunlight-driven chemical reactions that spurred the creation of more and more complex chemical compounds.
An earlier meteor that exploded over Murchison, Australia, in 1969 had similar features. Amino acids discovered in its clay, Joshua Sokol reported in Science, helped spread the idea that life on Earth may have originated from chemicals delivered in meteorites. And like the Murchison meteorite, this Aguas Zarcas fragment contains dust from the ancient, earlier Milky Way, before our sun formed.
Studies of this new meteorite are still incomplete, Sokol wrote. But researchers are excited that they can examine it using modern techniques, looking for complex organic compounds —— maybe even proteins —— that even if they did once exist inside the Murchison meteorite have long since disappeared, degrading in Earth's atmosphere. (The Murchison meteorite very closely resembled Aguas Zarcas, and if Aguas Zarcas contained proteins then Murchison probably did as well, though the opportunity to detect them has been lost.) Already, there's evidence of amino acids in this Aguas Zarcas fragment not found elsewhere on Earth.
Aguas Zarcas shards may offer the most pristine samples yet of the early solar system and pre-solar dust cloud. But landing as they did in the Costa Rican rainforest, Sokol reported, there's still the possibility of contamination.
Down the road, even more pristine samples may become available. The Japanese Hayabusa2 probe, launched in 2014 with the goal of sampling the asteroid Ryugu, is already on its way back with Ryugu dust onboard, a sample that may contain carbonaceous chondrite, Sokol noted. And in 2023, NASA will return its own samples from a similar asteroid, Bennu, which Sokol reported is likely related to Aguas Zarcas.
"These asteroid scraps will be truly pristine, having never touched the atmosphere or sat atop rainforest soil," Sokol wrote.
But for now, Aguas Zarcas is the best source of spacefaring carbon compounds available.
Originally published on Live Science.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.
Quoting from the article:Reply
"The Japanese Hayabusa2 probe, launched in 2014 with the goal of sampling the asteroid Ryugu, is already on its way back with Ryugu dust onboard, a sample that may contain carbonaceous chondrite, Sokol noted.
These asteroid scraps will be truly pristine, having never touched the atmosphere or sat atop rainforest soil," Sokol wrote."
Apparently Sokol (referring to the sample as "pristine") has not heard of solar and cosmic radiation. Since their sample was taken from the surface of the asteroid instead of a deep core sample, it is difficult to understand how it can be "truly pristine". One imagines that billions of years of intense radiation might have a significant impact on the chemical composition of organic compounds.
Actually it is not only Sokol who refers to such samples as "pristine". There seems to be a consensus among these scientists that their studies are attempting perfection from "pristine" samples, which is over-sold based on what has been analyzed so far. Any attempts at sampling pristine material would require substantial bore samples, and even then you would need data from several depths to confirm the findings. The composition of surface material would likely be vastly dissimilar to deep core samples, and nearly impossible to "deconvolute" to obtain its original chemistry.
In any event, this radiation might result in both assembly and degradation of compounds, depending on exposure levels and organic content. Inorganic content could also play a role in both mechanisms, with some possibly catalytic as well as stereo-selective. All of life on earth uses a number of stereo-isomers, particularly polymers.
Still, it remains very interesting that these objects are the source of a wide variety of abiotic organic chemicals that seeded the earth for abiogenesis to begin some 4 bya.
"One imagines that billions of years of intense radiation might have a significant impact on the chemical composition of organic compounds."Reply
Indeed. And intense solar UV radiation is the problem for life to evolve on the early Earth as well as life on Mars, in the past or even now.
Chem721 said:Apparently Sokol (referring to the sample as "pristine") has not heard of solar and cosmic radiation. Since their sample was taken from the surface of the asteroid instead of a deep core sample, it is difficult to understand how it can be "truly pristine".
Sokol is referring to the sample not being contaminated with Earth material and especially organics or prokaryote processes, which would confuse whether or not the material is produced biotically (most likely) or abiotically.
It is a good point that radiation skews mineral and molecule compositions, but they can account for some or all of that bias. (Say, by having samples from differing depth, which they took IIRC by sampling the initial surface and after an impactor had gouged it.)
Yes, the demonstration of organics all over the universe - from the atmosphere of carbon stars and out - is interesting for astrobiology, I think that is the main finding in these cases.
Broadlands said:And intense solar UV radiation is the problem for life to evolve on the early Earth as well as life on Mars, in the past or even now.
Your usual response to anything in astrobiology, whether irrelevant or not. (Not, in this case.) Also a claim dearly in need of reference.
Meanwhile, as far as we can probe biology, the universal ancestor lineage evolved in the deep ocean far from any UV production of compounds https://www.nature.com/articles/nmicrobiol2016116 ].
Certainly lends credence to .
Biblical passages (Christian or otherwise) are all well and good
On the contrary I think, it is generally considered rude to post erroneous superstition on a science site. C..f how people do not intrude on these sects' magic rituals to proclaim on known facts that reject the empirical basis for such ritual, that would be bad manners as well as disruptive.. While rude manners is understandable as all the argument they have, it is still not excusable.
Especially rude is the idea of large scale magic agency now, it is certainly not the case that there is an "absence of science". (Remember that agnosticism too is belief "in the absence of science".) We now know that space is flat, so the universe is a zero energy system, and its expansion is adiabatic, so it is a zero work system - it is on large scales entirely spontaneous process and spontaneous beginnings (if any - inflation before the hot big bang is naturally eternal). No magic agency 'created' the universe or acted within it, we can easily observe that now with the latest generation of cosmological surveys.
It doesn't matter Mr. Larsson, if its a usual response or not. What matters is if it is the truth or not. No reference is needed for the effect of intense UV radiation on DNA. UV lamps are routinely used. What does matter is that the last common ancestor at the base of the tree of life is a microbial hyperthermophile that is also an microAEROphile. Aquifex species are aerobic hyperthermophiles that use elemental sulfur, hydrogen, and trace amounts of OXYGEN in ecosystems near hot hydrothermal vents (Stetter, 1991). Not likely on an early Earth supposedly anoxic for a billion years.Reply
Broadlands said:It doesn't matter Mr. Larsson, if its a usual response or not. What matters is if it is the truth or not. No reference is needed for the effect of intense UV radiation on DNA. UV lamps are routinely used.
"What matters is if it is the truth or not." Indeed, there is nothing more important than the truth!
No doubt about the irradiation effects of UV on DNA, Very nasty to be sure. Tears it apart.
In any event, the fossil evidence indicates that life "surfaces" from the depths very early, probably a little under 4 bya. If there was significant UV radiation, it would have perished, unless its protein content was 50% DNA repair mechanisms, a highly unlikely scenario.
" If there was significant UV radiation, it would have perished.." Exactly. That's precisely why the standard view of the anoxic atmosphere / ocean origin of life and history of early life is not correct. And the reason why there was never any life on Mars. Without an ozone screen there could be no life. No oligonucleotides or polypeptides (leading to nucleic acids and proteins) that require the input of energy and the loss of water.Reply
One of the most likely events leading to a "rapid" oxygenated atmosphere is for the evolution of the photosynthetic reaction center (PRC) relatively early in some surface life form(s), which arose following their formation in the ocean's depths. The PRC is a remarkably complex mechanism that extracts energy from the sun and converts it into sugar. One of its primary bi-products is, of course, oxygen.Reply
Much of the evolution of this mechanism would likely have occurred in relatively shallow water, where UV could not penetrate very deeply at any rate, but the light that powers the PRC is in the visible range, which will do no damage to DNA. So one can see how the oxygenation can occur with the most primitive photosynthetic algae, prior to their organization into stromatolites. Some of these mats have been dated to ca. 3.7 bya. If this is correct, the original algae would likely have arose a few hundred million years before this, since evolution was not exactly galloping along almost 4 bya!
Not only do Aquas Zarcas and Murchison contain the building blocks of life, they probably came from a minor Solar system body on which life originated before migrating to Earth. Two less modified carbonaceous chondrites, Allende and Acfer-086, probably contain the first protein Hemolithin, presumably from the same body. Unlike the Earth, a minor solar system body can easily have deep freezing/thawing cycles and a closed hydrological system with desalination by freezing. These can concentrate chemicals necessary for life enough to favor the formation of early biomolecules, e.g., Hemolithin.Reply