Using data from the Curiosity rover, carbonate minerals containing abnormally high amounts of heavy carbon and oxygen isotopes have been discovered in Gale Crater on the Red Planet. The discovery provides important information about what the climate was like on Mars billions of years ago. Despite the inhospitable and cold surface of Mars, the search for traces indicating the existence of life here in the past continues. In this regard, scientists are helped by robotic devices that scratch the surface of Mars, especially NASA’s Curiosity rover.

The discovery was made using Sample Analyzers (SAM) and a Tunable Laser Spectrometer (TLS) mounted on the rover to measure the isotopic composition of carbonates, carbon-containing minerals that formed between 3.6 and 3.2 billion years ago. The study was published in the journal Proceedings of the National Academy of Sciences.

Recall that carbonates preserve the ratio of isotopes of elements and oxygen for a long time, allowing scientists to understand the composition of water and the atmosphere at the time of the formation of carbonate minerals, even if it occurred millions and billions of years ago.

Carbonates found in Gale Crater were found to be enriched in carbon-13 and oxygen-18 isotopes at levels well above those seen in other Martian rocks previously studied. Thus, scientists obtained new data on how the ancient Martian climate, potentially suitable for life, acquired the features observed today.

“The isotope values ​​indicate extreme levels of evaporation and suggest that these minerals formed in a climate that could only support the temporary existence of liquid water,” said study co-author David Burtt of NASA’s Goddard Space Flight Center.

Scientists have evaluated two main mechanisms that contribute to the enrichment of carbonate minerals with heavy isotopes of carbon and oxygen: evaporative separation and cryogenic precipitation. The most likely explanation for the isotopic values ​​is probably a combination of these mechanisms.

The first scenario describes a process in which light isotopes of water and carbon dioxide evaporate faster, while the remaining liquids become enriched with heavy isotopes, which can lead to a gradual increase in the content of carbon-13 and oxygen-18 in dissolved substances. carbonates then precipitate.

According to the second scenario, at low temperatures on the surface of Mars, cryogenic solutions could form in which heavier atoms of certain elements are located closer to the bottom and lungs closer to the top of the solution.

The researchers noted that the two mechanisms represent two different climate regimes: wet-dry climate cycles indicate switching between more and less habitable conditions, while cryogenic temperatures in Mars’ mid-latitudes indicate a less habitable environment.

The results highlight important differences between the carbon cycle of Mars and Earth. On our planet, the biosphere actively affects the distribution of carbon and its isotopes, but on Mars unique geochemical processes are observed, devoid of significant biological activity.

The authors of the new study concluded: “Concentrations of heavy carbon and oxygen isotopes in Gale Crater are higher than similar values ​​previously measured on Earth or the Red Planet, indicating extreme processes on Mars.”

To better understand the prevalence and variability of isotopic anomalies, the team plans to continue studying carbonates in different regions of Mars. The data obtained within the scope of the new study sheds light on mineral formation processes and provides important information about the planet’s climate and carbon cycle.