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Media type:
E-Article
Title:
Heterogeneous Processes in the Atmosphere of Mars and Impact on H2O2 and O3 Abundances
Contributor:
Daerden, Frank;
Crowley, John N.;
Neary, Lori;
Smith, Michael D.;
Loeffler, Mark J.;
Clancy, R. Todd;
Wolff, Michael J.;
Aoki, Shohei;
Sagawa, Hideo
imprint:
American Geophysical Union (AGU), 2023
Published in:Journal of Geophysical Research: Planets
Description:
<jats:title>Abstract</jats:title><jats:p>Current models underestimate the highest observed ozone (O<jats:sub>3</jats:sub>) column densities on Mars. These estimates could be improved by including the uptake of odd hydrogen species (HO<jats:sub><jats:italic>x</jats:italic></jats:sub>) on water ice clouds, but the reported uptake coefficient of HO<jats:sub>2</jats:sub> is likely overestimated for atmospheric conditions. This leaves a fundamental problem in Mars' atmospheric chemistry unsolved. Here, using the GEM‐Mars general circulation model, we explore a range of processes involving multiple phases (gas, adsorbed and solid) that may contribute to an alternative solution. First, we focus on hydrogen peroxide (H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>) and discuss its physical states on Mars and its chemical impact. We also conjecture its photolytic destruction in ices with model simulations and Compact Reconnaissance Imaging Spectrometer for Mars observations. Then, we include in the model all relevant (for Mars) heterogeneous reactions, both on dust and water ice, recommended by the International Union of Pure and Applied Chemistry for terrestrial atmospheric studies. We find that only the uptake of HO<jats:sub>2</jats:sub> and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> on dust are efficient on Mars. Finally, we find that attenuation of sunlight by water ice clouds in the calculation of photolysis rates leads to increased O<jats:sub>3</jats:sub> and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> abundances below the ice clouds. The combination of the proposed processes leads to O<jats:sub>3</jats:sub> increases without the need for strong uptake of HO<jats:sub>2</jats:sub> on ice, but it remains difficult to find a good agreement with O<jats:sub>3</jats:sub> and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> observations on the global scale. We provide specific recommendations for future work in observations, laboratory experiments and modeling to advance our understanding of fundamental chemistry on Mars.</jats:p>