Organic carbon concentrations in 3.5-billion-year-old lacustrine mudstones of Mars

The Sample Analysis at Mars instrument stepped combustion experiment on a Yellow-knife Bay mudstone at Gale crater, Mars revealed the presence of organic carbon of Martian and meteoritic origins. The combustion experiment was designed to access refractory organic carbon in Mars surface sediments by heating samples in the presence of oxygen to combust carbon to CO2. Four steps were performed, two at low temperatures (less than similar to 550 degrees C) and two at high temperatures (up to similar to 870 degrees C). More than 950 mu g C/g was released at low temperatures (with an isotopic composition of delta C-13 = +1.5 +/- 3.8) representing a minimum of 431 mu g C/g indigenous organic and inorganic Martian carbon components. Above 550 degrees C, 273 +/- 30 mu g C/g was evolved as CO2 and CO (with estimated delta C-13 = -32.9 to -10.1 for organic carbon). The source of high temperature organic carbon cannot be definitively confirmed by isotopic composition, which is consistent with macromolecular organic carbon of igneous origin, meteoritic infall, or diagenetically altered biomass, or a combination of these. If from allochthonous deposition, organic carbon could have supported both prebiotic organic chemistry and heterotrophic metabolism at Gale crater, Mars, at similar to 3.5 Ga.

Automated summary

The analysis of Mars samples from Gale crater revealed the presence of organic carbon from both Martian and meteoritic origins. The experiment showed that there is approximately 431μg C/g of indigenous organic and inorganic carbon on Mars. The source of high-temperature organic carbon remains uncertain, possibly coming from igneous organic carbon, meteorites, or diagenetically altered biomass.