One objective of the Curiosity rover is to search for habitable conditions, past and present, on the surface of Mars. Carbonate minerals can record diagnostic signatures of their formation environment. This paper focuses on carbon and oxygen isotope measurements of carbonate minerals detected within the Gale crater. Notably, these carbonates are extremely enriched in 13C and 18O, more so than other Martian materials. We highlight two processes (evaporation-driven Rayleigh distillation and cryogenic precipitation) that could explain these isotopic enrichments and explore whether those processes are consistent with our current understanding of Mars. These isotopic values offer a poignant example of how the Martian carbon cycle differs from that on Earth without the influences of a biosphere.
Burtt et al. (Mon,) studied this question.