Interannual and Diurnal Variability in Water Ice Clouds Observed from MSL Over Two Martian Years

Abstract

AbstractWe update the results of cloud imaging sequences from the Mars Science Laboratory (MSL) rover Curiosity to complete two Mars years of observations (LS=160° of Mars year (MY) 31 to LS=160° of MY 33). Relatively good seasonal coverage is achieved within the study period, with just over 500 observations obtained, averaging one observation every 2–3 sols. Cloud opacity measurements are made using differential photometry and a simplified radiative transfer method. These opacity measurements are used to assess the interannual variability of the aphelion cloud belt (ACB) for MY 32 and 33. Upon accounting for a statistical bias in the data set, the variation is found to be <30% within uncertainty. Diurnal variation of the ACB is also able to be examined in MY 33 owing to an increased number of early morning observations in this year. Although a gap in data around local noon prevents a complete assessment, we find that cloud opacity is moderately increased in the morning hours (07:00–09:00) compared to the late afternoon (15:00–17:00).