H$_2$O$_2$-induced Greenhouse Warming on Oxidized Early Mars

TL;DR

This study proposes that H₂O₂ could have significantly contributed to warming early Mars' oxidized atmosphere, enabling liquid water stability without reduced greenhouse gases, based on atmospheric modeling of H₂O₂'s infrared absorption.

Contribution

It introduces the novel idea that H₂O₂ alone could have warmed early Mars' oxidized environment, challenging previous assumptions about greenhouse gas requirements.

Findings

1 ppm of H₂O₂ can raise surface temperature above 273 K at 3 bar CO₂.

H₂O₂ can be sustained in the upper atmosphere due to photochemical production.

Oxidized early Mars could have maintained a warm, wet environment with H₂O₂ as a greenhouse agent.

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.