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Carbon signature found on Mars may be of biological origin

Carbon is the essence of life. But not only that… So when astronomers got their hands on a rather special form of carbon on Mars, they thought it could be produced by life. But not only…

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It’s been almost 10 years now curiosity Gale Crater trip. Ten years since plow referred to by NASA astronomer data that helps them to gradually reconstruct history planet Mars. And today, researcher reported that he had found disturbing markings in Martian soil samples. The kind of signature associated with our good old Earth… with a biological process!

Does this mean astronomers have finally gotten to the Grail? That they had found evidence of the existence of forms life beyond the earth? Let’s not go too soon. Because even though the researchers qualified their observations as“Very interesting”, they have also thought of another reasonable process to explain it. Scenario “unconventional”, of course, but that must be investigated before it can be closed.

But what did they actually find? Rocks with isotopic composition carbon startling. Remember that carbon has two stable isotopes. Carbon 12 and carbon 13. And because the former reacts more rapidly than the latter, analysis of their relative amounts in the sample provides researchers with useful information. In sedimentary rock analyzed by Curiosity, they found a sample that was very high in carbon 13 and another that was very low in carbon 13.

Galaxy or ultraviolet clouds

On earth, sediment also low in carbon 13 are those exposed to biological activity. A microbial mat that consumes methane (CH4), For example. But researchers can’t say for sure that the same kind of process occurs on Mars. The presence of carbon 13 depleted rocks may also be due to our travels Solar system In a cloud galaxy molecules – apparently every 200 million years – or by splitting carbon dioxide (C02) by ultraviolet (UV) radiation.

Is the first scenario possible? For this, astronomers report that the galactic cloud in question must first cause a temperature drop on Mars. To form glacier. Where dust can settle and be left behind as soon as the ice melts. Leaving layers of low-carbon-13 sediment behind, but so far there is only very limited evidence of the presence of glaciers in Gale Crater’s past.

Is UV orbit more promising? Here, nothing really leads us to conclude for now. Studies show that ultraviolet radiation can change CO2 in organic compounds of the formaldehyde type. But researchers will need more experimental results to confirm.

Biological signature?

With all the necessary precautions case, astronomers are also considering scenarios that would put extraterrestrial biological processes at the center of the story. Inspired by those known on earth. From bacteria surface that will produce a unique carbon signature by releasing methane intoatmosphere sniper. UV radiation will then convert it to molecule larger and more complex ones that would eventually rain down on the surface and can now be conserved with clear carbon signatures in Martian rocks.

“On Earth, the process by which the carbon signal we detect is biological, confirms Christopher House, researcher at Pennsylvania State University (United States of America). We need to understand whether the same explanation applies to Mars. ” Because the Red Planet is very different from us. Smaller, colder, with weaker gravity and a different mixture of early isotopes from Earth. “On our planet, there is life everywhere we look. And it affects the carbon cycle. Prevents us from learning what it would be like in the absence of life. »

Astronomers are now waiting to see if Curiosity will find similar signatures at other sites. They also hope to increase the carbon content of npsick with methane released by the surface as the rover accidentally crossed in 2019. A content that can confirm or not, the hypothesis involves microorganisms.

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