(ORDO NEWS) — It can hypothetically indicate the existence of alien life, but this is not certain.
The Curiosity rover has discovered an unusual chemical mixture containing carbon in Gale Crater on Mars. This discovery attracted a lot of attention from scientists, since carbon is considered one of the “markers” of life.
Traces of carbon have been identified in sediment samples collected over the past nine years, from August 2012 to July 2021. The rover took 24 samples and then heated them to release the gases they contained. Nearly half of these samples were found to contain surprisingly high amounts of carbon-12 compared to what was found in the Martian atmosphere and meteorites.
At the same time, some samples were enriched in carbon-13, and some were extremely depleted. According to scientists, this points to unconventional processes, different from those created by the carbon cycle in the modern era of the Earth.
On Earth, organisms predominantly use carbon-12 for their metabolic processes, so the enrichment of ancient rock samples with this isotope is usually interpreted here as a signal of biotic chemistry. But the carbon cycles on Mars are not well understood enough to make similar assumptions for finds on the Red Planet, members of the research team say.
“We are finding enticingly interesting things on Mars, but we really need more evidence to say that we have identified life.
So we’re looking into what else could have caused the carbon signature we’re seeing, if not life,” Paul Mahaffy, co-author of the study.
The scientists proposed three possible explanations for the intriguing carbon signal. The first scenario involves hypothetical Martian microbes producing methane, which is then converted into more complex organic molecules after interacting with ultraviolet (UV) light in the Red Planet’s atmosphere. These larger organics then made their way to the surface and were incorporated into the rocks that were selected by Curiosity.
However, similar reactions involving ultraviolet radiation and non-biological carbon dioxide – the most common gas in the Martian atmosphere – could theoretically lead to the same result.
A third explanation for the carbon signatures is a giant molecular cloud of dust. The solar system passes through one of these every couple of hundred million years or so, and the cooling effect it creates leaves carbon deposits behind. The team says this is a plausible scenario, but needs further study.
Curiosity has already detected organic compounds on Mars. For example, the mission team has previously reported finding organic matter in powdered rock samples. The six-wheeled robot has also repeatedly driven through methane streams, the origin of which on the Red Planet is still a mystery.
Theoretically, this compound could be produced by microbes actively metabolizing today beneath the cold Martian surface. Alternatively, methane could be produced from underground interactions between rocks and hot water, without the involvement of life. It could also be ancient material, produced by organisms or abiotically, that has been preserved under the surface for a long time and sometimes spills out.
The Curiosity team would like to drive through another methane plume and determine its carbon-12 content in order to further study the origin of these organic substances. But this will require a lot of luck, given that researchers cannot predict when and where such plumes will appear.
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