2005 Annual Science Report
University of Colorado, Boulder Reporting | JUL 2004 – JUN 2005
Biogeochemical Cycling and Resources on Mars
Our approach has been to examine the environmental conditions necessary to support life, and to understand their availability, accessibility, and abundance on Mars. We have been focusing primarily on availability of liquid water (and the connections to the history of climate and of volatiles) and the availability of geochemical energy that can support metabolism.
On the liquid water issue, there is increasing evidence to suggest that liquid water has been abundant at or near the surface at temperatures not significantly above ambient. That is, ambient temperatures rather than hydrothermal temperatures. The evidence comes from a variety of observations from the five spacecraft currently operating at Mars, and includes geological, atmospheric, polar, and geophysical analyses that relate to seasonal, obliquity, and four-billion-year timescales. We are in the process of synthesizing these results into a coherent picture of martian volatile evolution and liquid water availability. This synthesis differs from previous ones in significant ways, and represents a fundamental new paradigm of martian volatiles.
On the energy-availability issue, we have modeled the geochemical reactions between water and rock in Mars-like environments at ambient temperature conditions, in order to determine the availability of energy to support metabolism. We assume an initial set of minerals available for weathering at or near the surface, based on spacecraft and meteorite analyses. We use geochemical modeling software to determine the stable minerals that would result from weathering under a variety of assumptions, and then calculate the Gibbs free energy available from those reactions. This energy is theoretically available for organisms to utilize. Our results suggest that ambient-temperature conditions provide significantly more energy from weathering than do hydrothermal conditions, due to the greater energy change at low temperatures; however, the energy may be made available at a slower rate. These results have significant implications for planning upcoming missions that are investigating the potential for life and for interpreting observations at Mars in terms of the potential ability of the planet to support life.