WARC DISCOVERIES

Preparing for in situ measurements of isotopic biosignatures on Mars

Variations in the isotopic compositions of elements have proven to be one of the most powerful means for detecting the environments and processes of life in rocks, but how do we take the capabilities of large laboratories on Earth to other planets such as Mars? The answer lies in developing miniature mass spectrometers that will fit the stringent size, weight, and power requirements of rover-based instrumentation, but this requires new and innovative methods for sample introduction and mass analysis. A promising approach utilizes tunable laser spectroscopy, a technique that will be used on the 2009 Mars Science Lab mission for in situ analysis of carbon on Mars. WARC investigator Max Coleman and colleagues have recently reported in Analytical Chemistry on the first application of tunable laser spectroscopy to sulfur isotope analysis, which, if adapted to instrumentation that will fly to Mars, will allow us to understand bacterial sulfur cycling through in situ measurement of ³⁴S/³²S ratios on Mars and to determine if Mars developed an ozone shield or an oxygenated atmosphere through measurement of ³³S anomalies. Future research will concentrate on improving analytical precision to the 0.05 % level and to miniaturize the sample introduction system.

Citation:
Christensen, LE, Brunner, B, Truong, KN, Mielke, RE, Webster, CR, and Coleman, M (2007) Measurement of sulfur isotope compositions by tunable laser spectroscopy of SO2.  Analytical Chemistry 79:9261-9268.  A PDF copy of the paper can be found here.

Posted January 11, 2008