MICROBIAL IRON-SULFIDE MINERALS AS BIOSIGNATURES FOR THE SEARCH OF LIFE ON MARS

On Earth, most iron sulfide mineral formation takes place in anoxic sedimentary environments, where sulfide is produced by sulfate-reducing microorganisms (SRM). SRM influence the physical properties and composition of iron-sulfide minerals (1, 2), suggesting that iron-sulfide minerals could be used as a proxy for the detection of microbial life in anoxic environments on other planets, such as Mars. The presence of iron-sulfide minerals in the subsurface of Mars has been suggested in previous studies, and our experimental studies could help decipher if Martian iron-sulfide minerals have a biological origin, have been influenced by prebiotic molecules, or are of abiotic origin. In this presentation, I will discuss the robustness of the biosignature suite associated with iron sulfide minerals, and will present new data on the evolution of iron-sulfide minerals submitted to oxidizing conditions, simulating exposure to the surface of Mars.

1. Picard A, Gartman A, Clarke DR, & Girguis PR (2018) Sulfate-reducing bacteria influence the nucleation and growth of mackinawite and greigite. Geochimica et Cosmochimica Acta 220:367-384. 2. Picard A, et al. (in review) Authigenic metastable iron sulfide minerals preserve microbial organic carbon preservation in anoxic environments. Chemical Geology.