Evidence for Calcium Carbonate at the Mars Phoenix Landing Site

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Science  03 Jul 2009:
Vol. 325, Issue 5936, pp. 61-64
DOI: 10.1126/science.1172768

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Carbonates are generally products of aqueous processes and may hold important clues about the history of liquid water on the surface of Mars. Calcium carbonate (approximately 3 to 5 weight percent) has been identified in the soils around the Phoenix landing site by scanning calorimetry showing an endothermic transition beginning around 725°C accompanied by evolution of carbon dioxide and by the ability of the soil to buffer pH against acid addition. Based on empirical kinetics, the amount of calcium carbonate is most consistent with formation in the past by the interaction of atmospheric carbon dioxide with liquid water films on particle surfaces.

  • Present address: Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA.

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