2010 Annual Science Report
NASA Ames Research Center Reporting | SEP 2009 – AUG 2010
Mineralogical Traces of Early Habitable Environments
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 more life 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.
Efforts during this performance period have focused on (i) development and application of cell-scale bioenergetic models; (ii) characterization of mineralogy in samples collected from relict alteration deposits of the Josephine Ophiolite Complex and Spitzbergen, Norway; and (iii) parallel characterization of aqueous chemistry and biological diversity in samples collected from several actively serpentinizing systems.
(i) We have developed a cell-scale reaction transport model for determining single cell power generation for a defined metabolism in a medium of specified composition. The model determined diffusion in three dimensions (using a spherical cell), and includes biologically-realistic membrane transport properties. Model results are compared to estimates of cellular energy demand to estimate maximum growth rates and steady-state biomass density for specified conditions. We have applied the model for (a) characterization of energy balance in field sites with suitably-characterized conditions, and (b) estimation of changes in growth and biomass density potential for methanogenic metabolism across a range of parameter space relevant to serpentinizing systems. Results have been presented in talks at the 2009 Fall AGU meeting, AbSciCon 2010, the 13th International Society for Microbial Ecology Meeting, and the Extremophiles 2010 meeting.
(ii) We conducted bulk mineralogical analyses on samples collected from the Josephine Ophiolite Complex (Figure 1) and Spitzbergen, Norway (Figures 2 and 3), as the basis for a mineralogical assessment of habitability, and to augment a library of reference spectra for instruments that will fly on MSL. Samples were analyzed by an analog of the CheMin instrument, and by a Mössbauer spectrometer analogous to that on the MER rovers. A portion of these analyses supported the detection of the Comanche carbonates on Mars, as reported by Co-I Morris in a 2010 publication in Science.
(iii) We conducted paired analyses of aqueous chemistry and presence or absence of functional genes associated with target metabolisms, in samples collected from a range of actively serpentinizing systems. Chemistry measurements were used to determine Gibbs energy availability and, in some cases, power availability (via the modeling described in (i)). Assessment of functional genes was used to screen for metabolisms predicted by energetic modeling to be favorable under in situ conditions. Results were presented at the 2009 Fall AGU meeting and AbSciCon 2010, and in a publication in Northeastern Naturalist.
PROJECT INVESTIGATORS:Tori Hoehler
PROJECT MEMBERS:David Blake
Bo Barker Jørgensen
RELATED OBJECTIVES:Objective 2.1