Exploring the impact of wind-driven saltation on methane in the atmosphere of Mars

The presence or absence of methane in the atmosphere of Mars has been a matter of intense investigations and debate for decades. Current theories and observations require some as-yet unidentified mechanism that can remove methane from the lower martian atmosphere on a timescale of a few weeks or less.

In this work, we experimentally tested if methane sequestration by wind-driven saltation of martian surface minerals can explain the observations. Triboelectric charging of sand particles during the frequent martian dust storms could potentially provide the energy needed to chemically sequester methane and thereby act as a sink for methane on Mars. We performed laboratory experiments with basaltic martian mineral analog sand from Gufunes, Iceland, which was abraded by tumbling end-over-end in a container made from a monolithic block of the same mineral. In this way, wind-driven saltation was simulated in an all-basalt environment with minimal interference from wall-effects.

The results show that methane is not affected during more than 100 terrestrial days of simulated saltation in the all-basalt environment. This stands in contrast to similar experiments using quartz or glass simulation containers. Furthermore, methane remains unaffected by saltation in the presence of excess amounts of Mars-relevant oxidants, such as oxygen and perchlorate salt, which again contrasts to experiments performed in glass containers. However, methane is oxidized to carbon dioxide in the presence of reactive hypochlorite salt. Our results are discussed in the context of recent reports on the chemistry of oxychlorine species on Mars, and they highlight the need to account for wall-effects in experimental simulations of wind-driven saltation in planetary environments.