H 2 O 2 -induced Greenhouse Warming on Oxidized Early Mars

Abstract

The existence of liquid water within an oxidized environment on early Mars has been inferred by the Mn-rich rocks found during recent explorations on Mars. The oxidized atmosphere implied by the Mn-rich rocks would basically be comprised of CO 2 and H 2 O without any reduced greenhouse gases such as H 2 and CH 4 . So far, however, it has been thought that early Mars could not have been warm enough to sustain water in liquid form without the presence of reduced greenhouse gases. Here, we propose that H 2 O 2 could have been the gas responsible for warming the surface of the oxidized early Mars. Our one-dimensional atmospheric model shows that only 1 ppm of H 2 O 2 is enough to warm the planetary surface because of its strong absorption at far-infrared wavelengths, in which the surface temperature could have reached over 273 K for a CO 2 atmosphere with a pressure of 3 bar. A wet and oxidized atmosphere is expected to maintain sufficient quantities of H 2 O 2 gas in its upper atmosphere due to its rapid photochemical production in slow condensation conditions. Our results demonstrate that a warm and wet environment could have been maintained on an oxidized early Mars, thereby suggesting that there may be connections between its ancient atmospheric redox state and possible aqueous environment.