Glassy Subaqueous Lavas as a Habitat for Life on Earth, Mars, and Elsewhere?

Introduction: Numerous studies over the past decade have demonstrated that microbial life rapidly colonizes terrestrial subaqueous volcanic glass [1-5]. Evidence for microbial alteration of terrestrial subaqueous volcanic rocks has been reported from modern ocean crust, ophiolites, and Archean greenstone belts [1-5]. Microbial alteration structures with characteristic granular and tubular morphologies are produced by microbial etching of glassy lavas. These structures are preserved in the geological record via mineralization by a variety of phases including titanite (CaTiSiO5). It is hypothesized that microbes alter the local pH to enhance glass dissolution, and may extract chemical energy and nutrients such as Fe, Mg, Mn, Co and Zn. It is proposed that metabolically unimportant elements including Ti are passively accumulated in this process; Ti thus accumulated may then form titanite. Comparison of bioalteration textures throughout the terrestrial rock record to microbial alteration textures in modern seafloor glasses shows striking similarities, see Fig. 1. Exploration of these terrestrial biosignatures may elucidate the possibilities for the detection of traces of ancient Martian life in similar environments, and may inform the choice of future robotic/human sample return missions.