Dr. Samuel Kounaves
Professor
Department of Chemistry
Tufts University
United States of America
Biography
The Kounaves group research is aimed at unraveling fundamental questions in planetary science using modern in-situ analytical systems designed to study the biogeochemistry of extreme environments, where no one has gone before. As Co-I and Lead Scientist for the Wet Chemistry Lab (WCL) onboard NASA's Phoenix Mars Lander, Kounaves and his group performed the first wet chemical analysis of the martian soil using an array of electrochemical sensors. The experiments revealed an alkaline soil containing a variety of soluble minerals, but most surprising was the discovery of almost 1% perchlorate (ClO4-). Its discovery has wide ranging implications and has altered the way we view the chemistry of Mars and its potential to support life. The presence of perchlorate as Ca(ClO4)2 suggests that Mars' surface (at least around the Phoenix landing site) may have been severely arid for at least the past ~600 million years. The ClO4- may also be responsible for brines due to its depression of the H2O freezing point to -78ºC, the control of planet-wide soil and atmospheric water content, and the dificulty of instruments to detect organics (VL/GCMS; Phx/TEGA; & MSL/SAM). It could also act as an electron doner/energy source for any indigenous subsurface microbes, and is both good & bad for human explorers (can provide energy, fuel, and oxygen, but is human health hazard). The group's recent discovery, that ClO4- may form on any Cl-bearing mineral surface that is exposed to UV and that the process generates intermediary oxychlorines and highly oxidizing radicals, has implications not only for the production of ClO4- and the alteration/destruction of organics on Mars, but also on Earth and perhaps throughout the solar system and beyond. The discovery of perchlorate on Mars led the group to investigate the same possibility in Antarctica's McMurdo Dry Valleys. The study provided the first unambiguous discovery and clear evidence of the ubiquitous natural formation of perchlorate on Earth, with accumulation in arid environments and global atmospheric production. The discovery also suggests the hypothesis that the perchlorate reducing bacteria and arachea may be a remnant of a significant pre-oxygen Earth perchlorate ecosystem. The group has also recently confirmed ClO4-, ClO3-, and NO3-, in the Mars meteorites EETA79001 & Tissent, and also in lunar and chondrite meteorites. In addition to the current investigations exploring Mars' geochemistry and its potential for supporting past or present microbial life in surface or subsurface environments, their research (funded by NASA and NSF) includes understanding the geochemical and environmental history as recorded by the chemistry of planetary surface materials, and the geobiochemistry in extreme environments on Earth in places such as the McMurdo and other Antarctica Dry Valleys, Death Valley, the Tindouf Basin (Morocco), the Atacama Desert (Chile), and deep-ocean thermal vents. They are also interested in applying similar techniques to investigate the surface and sub-glacial oceans on icy moons such as Jupiter's Europa and Saturn's Enceladus. The group's research in astrobiology is focused on exploring concepts and analytical techniques for unambiguous detection of microbial life in extraterrestrial settings, and the survivability of organics on Mars' surface.
Research Interest
In-situ Planetary and Extreme Biogeochemical Analysis
Publications
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An Electrochemically Based Total Organic Carbon Analyzer for Planetary and Terrestrial On-Site Applications, S. T. Stroble and S. P. Kounaves, Anal. Chem., 2012, 84, 6271–6276.
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Effects of Extreme Cold and Aridity on Soils and Habitability: McMurdo Dry Valleys as an Analog for the Mars Phoenix Landing Site, L. K. Tamppari, R. M. Anderson, P. D. Archer Jr., S. Douglas, S. P. Kounaves, C. P. McKay, D. W. Ming, Q. Moore, J. E. Quinn, P. H. Smith, S. Stroble, A. P. Zent, Antarctic Science, 2012, 24, 211-228.
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Soluble Sulfate in the Martian Soil at the Phoenix Landing Site, S. P. Kounaves, M. H. Hecht, J. Kapit, R. C. Quinn, D. C. Catling, B. C. Clark, D. W. Ming, K. Gospodinova, P. Hredzak, K. McElhoney, and J. Shusterman, Geophys. Res. Lett., 2010, 37, L09201.
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Discovery of Natural Perchlorate in the Antarctic Dry Valleys and its Global Implications, S. P. Kounaves, S. T. Stroble, R. M. Anderson, Q. Moore, D. C. Catling, S. Douglas, C. P. McKay, D. W. Ming, P. H. Smith, L. K. Tamppari, A. P. Zent, Environ. Sci. Technol., 2010, 44, 2360-64.
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Wet Chemistry Experiments on the 2007 Phoenix Mars Scout Lander: Data Analysis and Results S. P. Kounaves, M. H. Hecht, J. Kapit, K. Gospodinova, L. DeFlores, R. C. Quinn, W. V. Boynton, B. C. Clark, D. C. Catling, P. Hredzak, D. W. Ming, Q. Moore, J. Shusterman, S. Stroble, S. J. West, and S. M. Young,. J. Geophys. Res., 2010, 115, E00E10.
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Detection of Perchlorate and the Soluble Chemistry of Martian Soil at the Phoenix Lander Site, M. H. Hecht, S. P. Kounaves, R. C. Quinn, S. J. West, S. M. M. Young, D. W. Ming, D. C. Catling, B. C. Clark, W. V. Boynton, J. Hoffman, L. P. DeFlores, K. Gospodinova, J. Kapit, and P. H. Smith Science, 2009, 325, 64-67.
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Evidence for Calcium Carbonate at the Mars Phoenix Landing Site, W. V. Boynton, D. W. Ming, S. P. Kounaves, et al., Science, 2009, 325, 61-64.
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H2O at the Phoenix Landing Site, P. H. Smith, L. K. Tamppari, R. E. Arvidson, D. Bass, D. Blaney, W. V. Boynton, A. Carswell, D. C. Catling, B. C. Clark, T. Duck, E. DeJong, D. Fisher, W. Goetz, H. P. Gunnlaugsson, M. H. Hecht, V. Hipkin, J. Hoffman, S. F. Hviid, H. U. Keller, S. P. Kounaves, et al., Science, 2009, 325, 58-61.
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The Origins of Perchlorate in the Martian Soil, B. L. Carrier and S. P. Kounaves, Geophys. Res. Lett., 2015, 42, 3739-3745
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Deliquescence-Induced Wetting and RSL-Like Darkening of a Mars Analogue Soil Containing Perchlorate and Chloride Salts, J. Heinz, D. Schulze-Makuch, and S. P. Kounaves, Geophys. Res. Lett., 2016, 43, 4880–4884
