Comparison between polar regions of Mars from HEND/Odyssey data

History and anatomy of subsurface ice on Mars

“…The pore ice created by diffusive back-filling extends close to equilibrium. The ice distribution that results from this climate scenario is consistent with the observed geographic distribution and burial depth of ice, but it is inconsistent with the high hydrogen content measured by neutron spectroscopy at high latitudes (Litvak et al, 2006;Feldman et al, 2004Feldman et al, , 2007, unless another mechanism operates to segregate ice after deposition and produces ice contents in excess of soil porosity (Fisher, 2005;Dash et al, 2006).…”

“…High ice concentrations, far in excess of porosity, are favored by neutron (Feldman et al, 2002(Feldman et al, , 2007(Feldman et al, , 2008Mitrofanov et al, 2002;Prettyman et al, 2004;Litvak et al, 2006), gamma-ray (Boynton et al, 2002), and radar (Mouginot et al, 2010) data, which points toward the presence of an ice sheet (Fig. 7b or c).…”

“…Evidence in favor of an ice sheet comes from neutron and gamma-ray spectroscopy, which indicate ice contents far in excess of soil porosity (Boynton et al, 2002;Feldman et al, 2002Feldman et al, , 2004Feldman et al, , 2007Mitrofanov et al, 2002;Prettyman et al, 2004;Litvak et al, 2006). Ground-penetrating radar measurements also suggest the amount of ice exceeds porosity (Mouginot et al, 2010).…”

“…1b, the pore ice layer in the south is thinner than in the north, poleward of about ±60°latitude. Litvak et al (2006) and Feldman et al (2008) determined that the water ice concentration in the southern high latitudes is higher than in the northern high latitudes. Hydrogen moderates neutrons so quickly that the neutrons thermalize within only a few centimeters of ice.…”

GRS evidence and the possibility of paleooceans on Mars

“…These instruments include the High Energy Neutran Detector (HEND), the Neutran Spectrameter (NS), and the GS; the three instruments of the GRS are designed to work synergistically to investigate the composition and nature of the near-surface Martian regolith . Analysis of the data acquired fram the GRS instrument suite has mapped the presence of significant subsurface ice deposits in regions poleward of appraximately 60" north and south latitudes Feldman et aL, 2002 ;Mitrafanov et aL, 2002 ;Litvak et aL, 2006 ), the distribution of H in low and mid latitudes Mitrafanov et aL, 2004;Fialips et aL, 2005 ), distinct elevated chlorine (CI) regions , and other elements such as K, Th, Fe, and silicon (Si) . These six elements of the Martian surface mapped thraugh GRS have also formed the basis for evaluating the variations in K/Th (Taylor et al, 2006a ), bulk composition (Taylor et al, 2006b ), composition of northern low-albedo regions (Karunatillake et aL, 2006 ), elemental abundances with respect to relative surface age (Hahn et aL, 2007 ), geochemistry of Martian soil and bedrack in mantled and less mantled terrains (Newsom et aL, 2007), and whether a giant ancient basin exists in Arabia Terra (Dohm et aL, 2007a).…”