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2012 Annual Science Report

NASA Ames Research Center Reporting  |  SEP 2011 – AUG 2012

Mineralogical Traces of Early Habitable Environments

Project Summary

The goal of our work is to understand how habitability (potential to support life) varies across a range of physical and chemical parameters, in order to support a long-term goal of characterizing habitability of environments on Mars. The project consists of two main components: 1. We are examining the interplay between physicochemical environments and associated microbial communities in a subsurface environment dominated by serpentinization (a reaction that involves water and crustal rocks, and which occurred on early Mars as indicated by observations of surface mineralogy). 2. We are working to understand how mineral assemblages can serve as a lasting record of prior environmental conditions, and therefore as indicators of prior habitability. This component directly supports the interpretation of mineralogy data obtained by the CheMin instrument on the Mars Science Laboratory.

4 Institutions
3 Teams
40 Publications
1 Field Site
Field Sites

Project Progress

This year’s efforts focused dominantly on an intensive characterization of the newly established borehole observatories at McLaughlin Natural Reserve (Fig. 1). Our program consists of an integrative suite of measurements that can be broadly categorized as follows:

Figure 1. Wellheads of the new borehole observatories sunk at McLaughlin provide a unique window into the serpentinizing subsurface.

Geology and Mineralogy: We performed an intensive mineralogical characterization of newly cored solids from the well-drilling operation, specifically using a commercial analog of the MSL mineralogy instrument CheMin. This specifically supports MSL by identifying mineral assemblages characteristic of active serpentinization, and tying them to the observed geochemistry. An important focus of this work was to quantify the abundance of magnetite as a proxy measure for total production of the microbial substrate H2 during serpentinization.

Geochemistry: We completed a year-long program of seasonal monitoring of newly drilled wells that charted the recovery of subsurface environmental conditions from the effects of drilling, and so we examined their changing chemistry (Fig. 2). Analyses focused on (i) abundance measurements of potential metabolites and other chemical species necessary to construct thermodynamic and bioenergetic models for metabolism; (ii) isotopic measurements designed to constrain potential sources of observed CH4; (iii) process rate measurements to seek evidence for microbial consumption of H2 and CO against a backdrop of varying pH levels. The latter formed the basis for an undergraduate research project for UC Berkeley student Addien Wray, who presented his results at AbSciCon 2012.

Figure 2. Freshly retrieved core materials during drilling operations at McLaughlin had pH values as high as 11.7. Following “recovery” of the newly drilled wells, fluids ultimately attained pH values up to 12.5, consistent with highly active serpentinization.

Microbial Community Analysis: We leveraged support from the Sloan Foundation “Census of Deep Life” and the Joint Genome Institute Community Sequencing Program in order to conduct tag-based deep sequencing analyses of microbial community composition in water and core materials from freshly drilled boreholes. These analyses will provide the basis for inter-comparison of community composition across McLaughlin samples (against a backdrop of changing pH and chemistry) and also for comparisons with other serpentinizing systems worldwide. Results thus far indicate a low diversity serpentinite biosphere consisting largely of Betaproteobacteria and Clostridiales. We have also obtained, using Sloan/CDL funding, the first of several metagenomes for samples from McLaughlin, in this case from near-surface samples at the newly drilled Core Shed Well borehole. Annotation of the sequences has just commenced, and early findings reveal areas of marked similarity in metagenome content to other serpentinizing sites, such as the Tablelands ophiolite in Newfoundland.

Outreach: We visited several classrooms during the year in order to explain how Earth-based research projects such as this one are important for informing our efforts to explore Mars (Fig. 3).

Figure 3. Postdoctoral associate Sanjoy Som talks to a class of elementary school students about Mars.