Data from the TGO probe revealed the cause of the abnormal ratio of carbon isotopes on the Red Planet. Previously, the version of the consequences of the vital activity of Martian bacteria was considered as one of its possible explanations.
The Martian atmosphere contains two carbon isotopes: light carbon-12, which makes up the vast majority of carbon in the Solar System, and heavy carbon-13 (a carbon-12 atom with an additional neutron). Their ratio is influenced by many short-term and long-term processes. Therefore, measuring their relative number can tell scientists about the past and present of the Red Planet.
During its mission, the Curiosity rover took several rock samples from Gale Crater, at the bottom of which a lake was once located. Their analysis showed an increased amount of the carbon-12 isotope and a depleted amount of carbon-13. If we were talking about the Earth, such a ratio would be interpreted in favor of the fact that the matter was processed by living organisms.
To determine the cause of the lack of carbon-13, scientists turned to the data of the TGO probe for help. In the spring of 2022, it conducted a series of measurements of the Martian atmosphere, determining the amount, composition and content of carbon at various altitudes.
The analysis showed that carbon dioxide molecules in the atmosphere of the Red Planet interact with sunlight and break apart, forming carbon monoxide depleted by heavy carbon. A similar process also occurs in the earth’s atmosphere.
To trace the fate of carbon monoxide, the researchers created a computer model. It demonstrated that its molecules were capable of forming organic compounds, which would then settle on the surface, forming carbon-13 depleted deposits. Thus, the presence of living beings on Mars is not required to explain the carbon anomaly.
Earlier we talked about why the Curiosity and Perseverance rovers were not able to detect life on Mars.
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