Enhanced Hydrogen Escape on Mars during the 2018 Global Dust Storm: Impact of Horizontal Wind Field

Abstract

Mars has undergone a substantial water loss, transforming from the early warm and wet state to the current cold and arid state. Observations and modeling efforts suggest that hydrogen escape is a metric of water loss on Mars. As a consequence of the vertical transport of water vapor by deep convection, hydrogen escape is significantly enhanced during Martian global dust storms. Motivated by the established scenario that the horizontal wind field could substantially enhance thermal escape, here we evaluate, for the first time, how the escape of H and H _2 on Mars during a typical global dust storm is modified by the enhanced horizontal wind field during the period. By combining kinetic model calculations and the Mars Climate Database outputs, we reach the conclusion that a nonnegligible enhancement of the H and H _2 escape flux could be driven by horizontal winds near the exobase, reaching 15% for H and 60% for H _2 at dawn near the equator during the dust storm. Although the enhancement of the global hydrogen escape rate by the horizontal wind is insignificant, it plays a crucial role in the redistribution of H and H _2 escape flux. The results presented here make useful contributions to a thorough understanding of enhanced hydrogen escape during the global dust storms.

Keywords

• Mars
• Upper atmosphere
• Exosphere
• Planetary atmospheres
• Solar system planets