Given the new evidence however, “The abundance and composition of the carbonates in the drill samples indicates a sedimentary pathway for carbonate formation and preservation on Mars. Siderite has been theoretically predicted to be a primary, early-forming sedimentary mineral on Mars.”

Moreover, as the Editor’s Summary at the beginning points out, “If there are similar abundances of carbonate in other sulfate-rich layers across Mars, then those layers may contain a substantial reservoir of carbon dioxide extracted from the atmosphere. The carbonates found by the authors have partially decomposed, returning some carbon dioxide to the atmosphere: an ancient carbon cycle.”