Microbial sulfate reduction in actively serpentinizing mantle rocks

Space Science & Astrobiology Division 
Special Seminar
 
N239 Conference Room 355
Tuesday, February 12th, 2019 — 3 pm 
 
 Clemens Glombitza
NPP Research Fellow (SSX)
 
Abstract: The last two decades of planetary exploration have identified a number of environments beyond Earth that may contain liquid water, including the sub-ice oceans of icy moons in the outer solar system. Attention focusses now on water-rock interactions to supply the energy and raw materials required by life. Serpentinization – the reaction of water with peridotite rocks – generates H2 and is thus of interest for its potential to support long-term habitability in subsurface environments, independent of photosynthesis. Peridotite rocks comprise Earth’s mantle, have been identified on the surface of Mars, and are probable components of the rocky interiors of the icy satellites Europa and Enceladus. Motivated by the seeming prevalence of sulfate in several potentially habitable environments beyond Earth we have started to investigate actively serpentinizing mantle rocks on Earth for the presence and environmental limitations of microbial sulfate reduction. We collected formation fluids from the Coast Range Ophiolite in California and the Semail Ophiolite in Oman that cover a range of different environmental conditions such as pH, sulfate, hydrogen and methane concentrations and measured microbial sulfate reduction by radio tracer incubations. Results show active microbial sulfate reduction in the fluids operating at very low rates and potentially limited by very high pH and concomitant low in-situ sulfate concentration. In January to March 2018, drill cores from three sites in the Semail Ophiolite were retrieved during the International Continental Scientific Drilling Program (ICDP) Oman Drilling Project (Phase II). At the drill-site, we have carefully selected and preserved core samples for a variety of microbiological investigations in different labs participating in the NAI Rock Powered Life. A sub-set of rock cores was prepared and incubated with radio tracer at Ames Research Center and a deeper insight into the presence and potential metabolic activity of the rock-hosted microbial sulfate reduction is expected in the near future.
 
POC: Mark A. Ditzler, mark.a.ditzler@nasa.gov