Atmospheric processes affecting methane on Mars

TL;DR

This paper investigates the atmospheric processes influencing methane's lifetime on Mars, highlighting discrepancies between models and observations, and suggesting unknown processes may be involved in methane's persistence.

Contribution

It estimates the impact of atmospheric chemistry and mixing on methane lifetime on Mars, revealing these processes alone cannot account for observed methane levels.

Findings

Atmospheric processes can only explain a sixteenfold reduction in methane lifetime.

Current models overestimate methane lifetime by about six hundred times.

Additional unknown processes are likely affecting methane's presence on Mars.

Abstract

It is currently uncertain as to whether methane exists on Mars. Data from the Curiosity Rover suggests a background methane concentration of a few tenths parts per billion whereas data from the Trace Gas Orbiter suggest an upper limit of twenty parts per trillion. If methane exists on Mars then we do not understand fully the physical and chemical processes affecting its lifetime. Atmospheric models suggest an over-estimate in the lifetime by a factor of around six hundred compared with earlier observations. In the present work we assume the Curiosity Rover background methane value and estimate the uncertainty in atmospheric chemistry and mixing processes in our atmospheric column model 1D TERRA. Results suggest that these processes can only explain a factor of ~sixteen lowering in the methane lifetime. This implies that if methane is present then additional, currently unknown processes are required to explain the observed lifetime.