The fast destruction of methane by heterogeneous electrochemistry induced by martian dust activity: An experimental approach

Abstract

Methane (CH 4 ) on Mars is of high scientific importance, particularly for its generation and destruction mechanisms. With an estimated photochemical lifetime of approximately 300 years, sporadic methane plumes observed on Mars by orbital, landed missions, and Earth-based telescopes suggest the presence of unknown destruction processes. Here, we present an experiment to examine CH 4 destruction through heterogeneous electrochemistry (HEC) triggered by Martian dust activities. We performed a series of mid-strength electrostatic discharge (ESD) experiments in mixtures of CO 2 and CH 4 under conditions relevant to the Martian near-surface atmosphere. We characterized (1) the free radicals produced from the breakdown of CH 4 and CO 2 ; (2) the gaseous and solid products of CH 4 and CO 2 decomposition; and (3) the half-life of CH 4 in this experiment. Based on a newly reported mission observation of electric discharge during a dust devil (DD) on Mars, we extrapolated the experimentally derived half-life to an approximate dust-devil-effective half-life of CH 4 on Mars, with uncertainties spanning orders of magnitude. The result demonstrates that dust-driven HEC can cause CH 4 destruction at rates hundreds to thousands of times faster than photochemistry. In future missions to Mars, if the knowledge gaps in the E-properties of dust activity are filled through regular measurements, this experimental finding may imply that Martian dust activity could be the primary factor reducing methane's lifetime, thereby contributing to understanding methane loss in the Martian atmosphere.