Resumen: The Gamma Ray Spectrometer (Mars Odyssey spacecraft) has revealed
elemental distributions of
potassium (K), thorium(Th), and iron (Fe) on Mars that require fractionation of K (and possibly Th and
Fe) consistent with aqueous activity. This includes weathering, evolution of soils, and transport, sorting,
and deposition, as well as with the location of first-order geomorphological demarcations identified as
possible paleoocean boundaries. The element abundances occur in patterns consistent with weathering
in situ and possible presence of relictor exhumed paleosols, deposition of weathered materials (salts
and clastic minerals), and weathering/transport under neutral to acidic brines. The abundances are
explained by hydrogeology consistent with the possibly over lapping alternatives of paleooceans and/or
heterogeneous rock compositions from diverse provenances (e.g., differing igneous compositions).
