Nasa’s Curiosity rover has uncovered evidence that ancient Mars had a carbon cycle, which increases the likelihood that the planet once harboured life.
Scientists have long presumed that Mars featured an active water cycle in the past, as the landscape shows clear signs that liquid water once flowed across its surface. This would have required a much warmer climate than the planet has today and a thicker atmosphere with higher carbon dioxide (CO2) concentrations.
While previous analyses of Martian rock have detected the presence of carbonates, the quantities found were lower than expected from geochemical models. But according to a recently published paper, data from three of Curiosity’s drill sites showed the samples contained siderite, an iron carbonate material.
The discovery of carbonate suggests that the atmosphere contained enough CO2 to support liquid water existing on the planet’s surface. As the atmosphere thinned, the CO2 transformed into rock form.
The carbonates discovered were...