Introduction: The OMEGA instrument on Mars Express has recently detected the largest gypsum deposit on Mars within the north polar sand sea [1]. Here we discuss the unique geologic context and origin of this evaporite deposit. Gypsum on Earth and Mars: Gypsum is a hydrated Ca-sulfate (2H 2 O • CaSO 4). Though gypsum can be formed, for example, as a hydrothermal deposit [e.g., 2] or as an altera...

a Woods Hole Oceanographic Institution and Earth Sciences Department, University of California at Santa Cruz, United States b Pacific Geoscience Center, Geological Survey of Canada, Sydney, B.C., Canada, V8L 4B2 c Earth Sciences Department, University of California at Santa Cruz, United States d Earth and Environmental Sciences, University of Illinois at Chicago, United States e Department of G...

M. Hagens, C. P. Slomp, F. J. R. Meysman, D. Seitaj, J. Harlay, A. V. Borges, and J. J. Middelburg Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands Department of Ecosystem Studies, Royal Netherlands Institute for Sea Research, Yerseke, the Netherlands Department of Analytical, Environmental and Geochemistry, Faculty of Science, Vrije Universitei...

a Northern Centre for Isotopic and Elemental Tracing, Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK b Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655, Hannover, Germany c Laboratoire de Minéralogie et Cosmochimie, Muséum National d'Histoire Naturelle and CNRS (UMR 7202), 61 rue Buffon, Paris 75005, France d Department of Geological S...