Global distribution of near‐surface hydrogen on Mars

Abstract

[1] Neutron data observed using the Neutron Spectrometer aboard 2001 Mars Odyssey provide a lower limit to the global inventory of Martian water-equivalent hydrogen. Hydrogen-rich deposits ranging between about 20% and 100% water-equivalent by mass are found poleward of ±50°latitude, and less rich, but significant, deposits are found at near-equatorial latitudes. The equatorial deposits between ±45°latitude range between 2% and 10% water-equivalent hydrogen by mass and reach their maximum in two regions that straddle the 0-km elevation contour. Higher water abundances, up to $11%, are required in subsurface regolith of some equatorial regions if the upper 10 g/cm 2 of regolith is desiccated, as suggested on average by comparison of epithermal and fast neutron data. The hydrogen contents of surface soils in the latitude range between 50°and 80°north and south are equal within data uncertainties. A lower-limit estimate of the global inventory of near surface hydrogen amounts to a global water layer about 14 cm thick if the reservoir sampled from orbit is assumed to be 1 m thick.

Polygon pattern geomorphometry on Svalbard (Norway) and western Utopia Planitia (Mars) using high-resolution stereo remote-sensing data

“…Larger polygons, however, are also formed in material with lower ice content (Lachenbruch, 1966) as was discussed for the terrestrial polygons (Table 1). No clear relationship between polygon dimension and ground-ice content, which increases with latitude (e.g., Feldman et al, 2004), could be observed on Mars (Mangold et al, 2004;Mangold, 2005;Levy et al, 2009a). The size of the upland polygons (UP1) is consistent with the findings of the Gamma Ray Spectrometer (GRS) that only~4 tõ 10 wt.% water-ice equivalent exists currently in the upper surface layer (b1 m depth) in the regions between 45°S and 45°N Mitrofanov et al, 2002;Feldman et al, 2004).…”

“…No clear relationship between polygon dimension and ground-ice content, which increases with latitude (e.g., Feldman et al, 2004), could be observed on Mars (Mangold et al, 2004;Mangold, 2005;Levy et al, 2009a). The size of the upland polygons (UP1) is consistent with the findings of the Gamma Ray Spectrometer (GRS) that only~4 tõ 10 wt.% water-ice equivalent exists currently in the upper surface layer (b1 m depth) in the regions between 45°S and 45°N Mitrofanov et al, 2002;Feldman et al, 2004). If higher ground-ice contents than in the upper layer occur deeper than 1 m, which was inferred from the dimension of the scalloped depressions (Morgenstern et al, 2007;Ulrich et al, 2010), seasonal thermal waves should not reach this depth at the present time (Mellon, 1997;Mangold et al, 2004).…”

Transverse Aeolian Ridges (TARs) on Mars

“…Gamma Ray Spectrometer and Neutron Spectrometer (GRS/NS) observations of regolith at latitudes N50-60°show substantial amounts of water ice within a few tens of centimeters of the surface (Boynton et al, 2002;Feldman et al, 2004). The soils may therefore have had a degree of cohesion from ice cement holding the grains together, resulting in little mobile sediment available for transport by the wind.…”

Mars Surface Mobility Leading to Sustainable Exploration

“…3,4 These discoveries have reignited the concept of making methane on Mars for propulsion with oxygen. Previously, the biggest drawback to the methane option was the need to bring hydrogen from Earth, which is difficult to store and transport due to its low density and liquefaction temperature.…”