Geobiological studies of both modern and ancient Mars-relevant environments on Earth have highlighted the potential for samples returned from Mars to contain viable microorganisms or their fossilized remains, while supporting the development of new approaches for in situ and laboratory detections of biosignatures in a variety of geological materials.

The committee found that uncertainties in the current assessment of martian habitability and of the potential for the inclusion of living entities in samples returned from Mars might be reduced by continuing research and development in the following areas:

  • Investigations of the prolonged viability of microorganisms in geological materials;

  • Studies of the nature and potential for biosignature preservation in a wide range of Mars-analog materials;

  • Evaluation of the impacts of post-depositional (diagenetic) processes (deep burial, impact shock, subfreezing temperatures) on the long-term retention of biosignatures in ancient geological materials;

  • Definition of reliable criteria for the definitive identification of biosignatures in ancient materials; and

  • Development of new laboratory-based and in situ analytical approaches to biosignature analysis.



1. J.D. Farmer and D.J. Des Marais, “Exploring for a Record of Ancient Martian Life,” Journal of Geophysical Research—Planets 104(E11):26977-26995, 1999.


2. B.A. Hofmann, J.D. Farmer, F. Von Blanckenburg, and A.E. Fallick, “Subsurface Filamentous Fabrics: An Evaluation of Origins Based on Morphological and Geochemical Criteria, with Implications for Exopaleontology,” Astrobiology 8:87-117, 2008.


3. J.D. Farmer, “Exploring for a Fossil Record of Extraterrestrial Life,” pp. 10-15 in Palaeobiology II (D. Briggs and P. Crowther, eds.), Blackwell Science Publishers, Oxford, U.K., 2000.


4. S.L. Cady and J.D. Farmer, “Fossilization Processes in Siliceous Thermal Springs: Trends in Preservation Along Thermal Gradients,” pp. 150-173 in Evolution of Hydrothermal Ecosystems on Earth (G.R. Bock and J.A. Goode, eds.), John Wiley and Sons Ltd., Chichester, U.K., 1996.


5. R.W. Renaut and B. Jones, “Microbial Precipitates Around Continental Hot Springs and Geysers,” pp. 187-195 in Microbial Sediments (R. Riding and S. Awramik, eds.), Springer, Berlin, 2000.


6. K.M. Handley, S.J. Turner, K.A. Campbell, and B.W. Mountain, “Silicifying Biofilm Exopolymers on a Hot-Spring Microstromatolite: Templating Nanometer-Thick Laminae,” Astrobiology 8:747-770, 2008.


7. B.W. Fouke, G.T. Bonheyo, B. Sanzenbacher, and J. Frias-Lopez, “Partitioning of Bacterial Communities Between Travertine Depositional Facies at Mammoth Hot Springs, Yellowstone National Park, U.S.A.,” Canadian Journal of Earth Sciences 40:1531-1548, 2003.


8. A. Pentecost, “Cyanobacteria Associated with Hot Spring Travertines,” Canadian Journal of Earth Sciences 40:1447-1457, 2003.


9. B.K. Pierson and M.T. Parenteau, “Phototrophs in High Iron Microbial Mats: Microstructure of Mats in Iron-depositing Hot Springs,” FEMS Microbiology Ecology 32:181-196, 2000.


10. M.L. Wade, D.G. Agresti, T.J. Wdowiak, L.P. Armendarez, and J.D. Farmer, “A Mössbauer Investigation of Iron-rich Terrestrial Hydrothermal Vent Systems: Lessons for Mars Exploration,” Journal of Geophysical Research—Planets 104(E4):8489-8507, 1999.


11. B.A. Hofmann, J.D. Farmer, F. von Blanckenburg, and A.E. Fallick, “Subsurface Filamentous Fabrics: An Evaluation of Origins Based on Morphological and Geochemical Criteria, with Implications for Exopaleontology,” Astrobiology 8:87-117, 2008.


12. D.C. Fernandez-Remolar and A.H. Knoll, “Fossilization Potential of Iron-bearing Minerals in Acidic Environments of Rio Tinto, Spain: Implications for Mars Exploration,” Icarus, 194:72-85, 2008.


13. K.C. Benison and B.B. Bowen, “Acid Saline Lake Systems Give Clues About Past Environments and the Search for Life on Mars,” Icarus 183:225-229, 2006.


14. K.C. Benison, “A Martian Analog in Kansas: Comparing Martian Strata with Permian Acid Saline Lake Deposits,” Geology 34:385-388, 2006.

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