The Curiosity mission began close to the underside of the crater, on the base of a formation known as Aeolis Mons, or Mount Sharp, the place NASA anticipated to search out the earliest geological samples. The concept then was to climb up Mount Sharp and acquire samples from later and later geological durations at growing elevations, tracing the historical past of habitability and the nice drying up of Mars. On the best way, the carbon missed by the satellites was lastly discovered.

An imperfect cycle

Tutolo’s staff targeted their consideration on 4 sediment samples Curiosity drilled after climbing over a kilometer up Mount Sharp. The samples have been examined with the rover’s Chemistry and Mineralogy instrument, which makes use of X-ray diffraction to find out their composition. It turned out the samples contained roughly between 5 and 10 p.c of siderite. “It was an iron carbonate, straight analogous to a mineral known as calcite present in sedimentary rocks like limestone. The distinction is it has iron in its cation website slightly than calcium,” Tutolo defined. “We anticipated that as a result of Mars is way richer in iron—that’s why it’s the pink planet.”

The siderite discovered within the samples was additionally pure, which Tutolo thinks signifies it has shaped by way of an evaporation course of akin to what we see in evaporated lakes on Earth. This, in flip, was the primary proof we’ve discovered of the traditional Martian carbon cycle. “Now we’ve proof that confirms the fashions,” Tutolo claims. The carbon from the environment was being sequestered within the rocks on Mars simply as it’s on Earth. The issue was, in contrast to on Earth, it couldn’t get out of those rocks.

“On Earth, each time oceanic plates get subducted into the mantle, the entire limestone that was shaped earlier than will get cooked off, and the carbon dioxide will get again to the environment by way of volcanoes,” Tutolo explains. Mars, alternatively, has by no means had environment friendly plate tectonics. A big portion of carbon that bought trapped in Martian rocks stayed in these rocks without end, scaling down the environment. Whereas it’s probably the pink planet had its personal carbon cycle, it was an imperfect one which ultimately turned it into the lifeless desert it’s immediately.