Mars's Twilight Cloud Band: A New Cloud Feature Seen During the Mars Year 34 Global Dust Storm

Abstract : 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 6000~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 these clouds formed as a result of semidiurnal thermal tides.