Martian dust storms as a possible sink of atmospheric methane

摘要

Recent laboratory tests, analog studies and numerical simulations all suggest that Martian dust devils and larger dusty convective storms generate and maintain large- scale electric fields. Such expected E- fields will have the capability to create significant electron drift motion in the collisional gas and to form an extended high energy ( u kT) electron tail in the distribution. We demonstrate herein that these energetic electrons are capable of dissociating any trace CH4 in the ambient atmosphere thereby acting as an atmospheric sink of this important gas. We demonstrate that the methane destruction rate increases by a factor of 10(12) as the dust storm E- fields, E, increase from 5 to 25 kV/ m, resulting in an apparent decrease in methane stability from similar to 10(10) sec to a value of similar to 1000 seconds. While destruction in dust storms is severe, the overall methane lifetime is expected to decrease only moderately due to recycling of products, heterogeneous effects from localized sinks, etc. We show further evidence that the electrical activity anticipated in Martian dust storms creates a new harsh electro- chemical environment.