Carbonate formation and fluctuating habitability on Mars.

The cause of Mars's loss of surface habitability is unclear, with isotopic data suggesting a 'missing sink' of carbonate. Past climates with surface and shallow-subsurface liquid water are recorded by Mars's sedimentary rocks, including strata in the approximately 4-km-thick record at Gale Crater. Those waters were intermittent, spatially patchy and discontinuous, and continued remarkably late in Mars's history-attributes that can be understood if, as on Earth, sedimentary-rock formation sequestered carbon dioxide as abundant carbonate (recently confirmed in situ at Gale).

Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars.

Ancient Mars had surface liquid water and a dense carbon dioxide (CO)-rich atmosphere. Such an atmosphere would interact with crustal rocks, potentially leaving a mineralogical record of its presence. We analyzed the composition of an 89-meter stratigraphic section of Gale crater, Mars, using data collected by the Curiosity rover.

Highly enriched carbon and oxygen isotopes in carbonate-derived CO at Gale crater, Mars.

Carbonate minerals are of particular interest in paleoenvironmental research as they are an integral part of the carbon and water cycles, both of which are relevant to habitability. Given that these cycles are less constrained on Mars than they are on Earth, the identification of carbonates has been a point of emphasis for rover missions. Here, we present carbon (δC) and oxygen (δO) isotope data from four carbonates encountered by the Curiosity rover within the Gale crater.