Oxidant Enhancement in Martian Dust Devils and Storms: Implications for Life and Habitability

摘要

We investigate a new mechanism for producing oxidants, especially hydrogen peroxide (H_2O_2), on Mars. Large-scale electrostatic fields generated by charged sand and dust in the martian dust devils and storms, as well as during normal saltation, can induce chemical changes near and above the surface of Mars. The most dramatic effect is found in the production of H_2O_2 whose atmospheric abundance in the "vapor" phase can exceed 200 times that produced by photochemistry alone. With large electric fields, H_2O_2 abundance gets large enough for condensation to occur, followed by precipitation out of the atmosphere. Large quantities of H_2O_2 would then be adsorbed into the regolith, either as solid H_2O_2 "dust" or as re-evaporated vapor if the solid does not survive as it diffuses from its production region close to the surface. We suggest that this H_2O_2, or another superoxide processed from it in the surface, may be responsible for scavenging organic material from Mars. The presence of H_2O_2 in the surface could also accelerate the loss of methane from the atmosphere, thus requiring a larger source for maintaining a steady-state abundance of methane on Mars. The surface oxidants, together with storm electric fields and the harmful ultraviolet radiation that readily passes through the thin martian atmosphere, are likely to render the surface of Mars inhospitable to life as we know it.