Mars has lost most of its initial water to space as atomic hydrogen and oxygen 1,2 . Spacecraft measurements have determined that the hydrogen component of this loss undergoes large variations with season 3-6 inconsistent with longstanding explanations 7,8 . The cause is incompletely understood, with likely contributions from seasonal changes in atmospheric circulation, dust activity, and solar extreme ultraviolet input. While some modeling and indirect observational evidence suggest dust activity can explain the seasonal trend [9][10][11][12][13][14][15] , no prior study has been able to unambiguously distinguish seasonal from dust-driven forcing. Here we present synoptic measurements of dust, temperature, ice, water, and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary H loss by a factor of 5-10. This regional storm occurred in the declining phase of the known seasonal trend, establishing that dust forcing can override this trend to drive enhanced escape. Because similar regional storms occur in most Mars years 16 , these storms may be responsible for a large fraction of Martian water loss, with implications for Mars atmospheric evolution and planetary habitability in general.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
We report a new water‐ice cloud feature observed during the Mars year 34 global dust storm: twilight cloud bands that routinely formed just past the evening terminator. We use images taken by the MAVEN/IUVS instrument. These bands were often latitudinally continuous, spanning over 6,000 km and were present between 18:00 and 19:00 local time. They were present for nearly the entire time IUVS imaged the evening terminator and often reached altitudes of at least 40 to 50 km during the mature phase of the storm. We compare these observations to LMD global climate model simulations. The simulations generally contain the temporal and spatial extents of the bands seen in IUVS data throughout the storm, but there are some discrepancies. We infer that these clouds formed as a result of semidiurnal thermal tides.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.