Hydrated states of MgSO₄ at equatorial latitudes on Mars

Abstract

[1] The stability of water ice, epsomite, and hexahydrite to loss of H 2 O molecules to the atmosphere at equatorial latitudes of Mars was studied to determine their potential contributions to the measured abundance of waterequivalent hydrogen (WEH). Calculation of the relative humidity based on estimates of yearly averages of watervapor pressures and temperatures at the Martian surface was used for this purpose. Water ice was found to be sufficiently unstable everywhere within 45°of the equator that if the observed WEH is due to water ice, it requires a lowpermeability cover layer near the surface to isolate the water ice below from the atmosphere above. In contrast, epsomite or hexahydrite may be stable in many near-equatorial locations where significant amounts of WEH are observed.

The sedimentology and dynamics of crater-affiliated wind streaks in western Arabia Terra, Mars and Patagonia, Argentina

“…We note that water activities corresponding to relative humidities of a few percent (relative to the vapor pressure of ice) are sufficient to stabilize some hydrated salts such as kieserite (Feldman et al, 2004). This hypothesis could explain the apparent low mobility of highalbedo dune forms by the creation of cements and duricrust by either aqueous precipitation or atmospheric driven hydration (Marion et al, 2003;Vaniman and Chipera, 2006;Marion et al, 2007).…”

Modeling ferrous–ferric iron chemistry with application to martian surface geochemistry

“…Which of these two cycles and the relative contribution of each for primary phase precipitation and subsequent diagenetic processes on Mars is still very much an open question. Also unsettled is the role of dehydration/hydration cycles involving solid hydratable salts and vapor phases but lacking a liquid phase, as should occur under conditions of exceeding low relative humidity (Feldman et al, 2004). The diagenetic effects of these processes, as on Earth, may substantially affect the extant mineral assemblages and affect our ability to interpret primary depositional environments and infer paleoclimates.…”

Selection of the InSight Landing Site

“…Recent reviews of clays and hydrated minerals on Mars show no detections in the plains of western Elysium (Ehlmann et al 2011;Ehlmann and Edwards 2014). Neutron spectrometer and Gamma Ray Spectrometer data show western Elysium Planitia to have low water equivalent hydrogen (4-5 %), consistent with minor amounts of bound water or OH in the martian soil (Feldman et al 2004a(Feldman et al , 2004bMitrofanov et al 2004;Boynton et al 2008). Mapping of strandlines (Parker et al 1993;Clifford and Parker 2001) and unconfined deltas (Di Achille and Hynek 2010) of a putative global northern ocean indicates the InSight landing site would have been underwater in the Noachian, but any water-rich deposits would be buried beneath 200 m of basalt.…”