2009 Annual Science Report

NASA Ames Research Center Reporting  |  JUL 2008 – AUG 2009

Mineralogical Traces of Early Habitable Environments

Project Summary

The goal of our work is to discern the habitability (potential to support life) of ancient Martian environments, with an emphasis on understanding which environments could have supported life more abundantly than others. This information will help to guide the selection of sites on the Martian surface, for future missions designed to seek direct evidence of life. Our approach has two main parts: 1. We will use the presence of specific minerals or groups of minerals – an analysis that can be performed robotically on Mars — to constrain the chemical and physical conditions of the ancient environments in which they formed. 2. We will work to understand how the ability of environments on Earth to support more or less biomass depends on these same physical and chemical conditions.

4 Institutions
3 Teams
33 Publications
1 Field Site
Field Sites

Project Progress

The initial stages of this project have focused principally on the initial characterization of field sites and on early development of reaction-transport models that calculate cellular energy balance as a function of geochemical environment.

We conducted a preliminary field expedition to the Josephine Ophiolite Complex (JOC) of Northern California in May 2009. Samples representing differing extents and styles of parent rock alteration were collected from each type section of the exposed ocean crust. For a subset of samples, we conducted XRD/XRF analyses in the field using a commercial version of the CheMin instrument that will fly on Mars Science Laboratory. Preliminary site observations and mineralogical characterization were presented at the 2009 GSA (Geological Society of America) meeting. Samples are presently being analyzed by Moessbauer, and thin sections have been prepared for spatially-resolved mineralogical analysis. The results of these analyses, along with bulk scale and contextual observations conducted on site, will help to direct a follow-up field trip to the JOC during spring/summer 2010.

Figure 1. Collecting samples from an alteration deposit associated with weathering peridotite rocks (Eight Dollar Mountain, Josephine Ophiolite Complex, CA).

A preliminary cell-scale reaction transport model for calculating “energetic habitability” has been developed. In its initial form, the model calculates methanogenic energy yields for a single spherical cell in an infinite medium of defined physics and chemistry (temperature, salinity, pH, and concentrations of H2 and ΣCO2). Energy yields are divided by estimates of cell-specific energy demand (initially treated a function of pH and temperature). This basic model has been applied to examine the habitability of fluids affected by serpentinization (i.e., elevated H2 and pH, and potentially decreased ΣCO2), across a range of relevant parameter space. A manuscript (“Bioenergetic and mass-transport constraints on microbial ecology in hydrothermal flow: a case study of methanogenesis in serpentinizing systems”) is being prepared for submission to JGR Biogeosciences.