NASA's Curiosity rover, currently exploring Gale crater on Mars, has provided new insights into how the ancient Martian climate transitioned from potentially suitable for life, with evidence of widespread liquid water, to its present inhospitable state. Researchers utilized instruments on Curiosity to analyze the isotopic composition of carbon-rich minerals (carbonates) found in Gale crater, revealing significant details about the planet's climatic evolution.
According to David Burtt of NASA's Goddard Space Flight Center, the isotopic values of these carbonates indicate extreme evaporation, suggesting they formed in a climate that could only support transient liquid water. While the findings do not confirm the existence of a biosphere on the Martian surface, they leave open the possibility of underground life or a biosphere that existed before the formation of these carbonates.
The study highlights the importance of carbonates as climate records, retaining signatures of their formation environments. Two potential formation mechanisms for the carbonates were proposed: one involving wet-dry cycles, indicating fluctuating habitability, and the other involving cryogenic conditions with salty water, suggesting a less hospitable environment.
Significantly, the heavy isotope values found in Martian carbonates are the highest recorded for any materials on Mars, indicating extreme processes at play. The findings, made using the Sample Analysis at Mars (SAM) and Tunable Laser Spectrometer (TLS) aboard Curiosity, underscore the complexity of Mars' climatic history and its implications for the search for past life.