On the thickness of the oxidized layer of the Martian regolith

A revised model of the diffusion of H2O2 through the Martian regolith is pr esented, which argues that oxidant diffusion may be more efficient than pre viously thought. Recent models of the adsorption of H2O at Mars-like condit ions indicate that it adsorbs more poorly than previously believed. H2O ads orption is a necessary proxy for peroxide adsorption; hence the adsorptive slowing of peroxide diffusion is modeled as less efficient. Because the per oxide has a finite lifetime, it has a finite extinction depth as well. The effects of regolith gardening by impacts are quantitatively estimated and c ombined with the effects of oxidation by atmospheric gases to produce estim ates of the degree of oxidation of the Martian surface with depth. We explo re the effects of different crater production populations along with variat ions in H2O2 extinction depths, and hydrothermal oxidation of ejects. In ve ry select circumstances involving very early onset of oxidizing conditions during heavy bombardment, 150-200 m of regolith could be fully oxidized. Mo re likely scenarios for the crater production population, onset of oxidizin g conditions, and oxidant extinction depth yield estimates of no more than a few meters to putative reducing material. In addition, uncertainties rema in regarding the degree to which hydrothermal or other high-temperature che mistry might oxidize materials in ejecta blankets. The trade-off between ac cessing unlithified sediments or rock interiors must be considered.