Free Astronomy Magazine March-April 2021

43 MARCH-APRIL 2021 MARS ROVERS T he rock “Ithaca” shown here, with a rougher lower texture and smoother texture on top, appears to be a piece of the local sedimentary bedrock protruding from the surround- ing soil in Gale Crater. [NASA/JPL- Caltech/MSSS] gence of life. Since the age of the rock structures of Yellowknife Bay are a little older than expected, those conditions have then lasted until more recent times than previ- ously believed. If we then consider that hydrogen, oxygen and nitro- gen have also been identified in the dry lakebed in addi- tion to the elements already mentioned, we find all the pre- requisites for micro- bial life to have proliferated in that environment and in other similar envi- ronments. But any confirmation in this sense can only come from Curiosity’s suc- cessors, starting with Perseverance. N ASA’s Curiosity Mars rover recorded this se- quence of views of the sun setting at the close of the mission’s 956 th Martian day, or sol (April 15, 2015), from the rover’s location in Gale Crater. The four images shown in sequence here were taken over a span of 6 minutes, 51 seconds. This was the first sunset observed in color by Curiosity. [NASA/JPL-Caltech/ MSSS/Texas A&M Univ.] that appeared in it. The analysis of the data collected by Curiosity has also shown that the clay sediments of Yel- lowknife Bay are rich in iron and sul- fur, elements that together with the clay form a mineral called smectite. This mineral forms in waters with neu- tral pH and low salinity, the ideal habitat for a primitive terrestrial life form called chemolithoautotrophs. These bacteria draw energy directly from the rock material by exploiting the oxidation of inorganic com- pounds, with sulfur and iron at the center of their diet, while using the supply of carbon that exists directly from an atmosphere rich in carbon dioxide. In a sense, chemolithoau- totrophs are powered by a sort of battery, and that kind of power supply was available in Yellowknife Bay. All this demonstrates that the geological environment of young Mars was conducive to the emer-