The first Martian year of cloud activity from Mars Science Laboratory (sol 0-800)

Using images from the Navigation Cameras onboard the Mars Science Laboratory rover Curiosity, atmospheric movies were created to monitor the cloud activity over Gale Crater. Over the course of the first 800 sols of the mission, 133 Zenith Movies and 152 Supra-Horizon Movies were acquired which use a mean frame subtraction technique to observe tenuous cloud movement. Moores et al. (2015a) reported on the first 360 sols of observations, representing L_S = 150°-5°, and found that movies up to L_S = 184° showed visible cloud features with good contrast while subsequent movies were relatively featureless. With the extension of the observations to a full Martian year, more pronounced seasonal changes were observed. Within the Zenith Movie data set, clouds are observed primarily during L_S = 3°-170°, when the solar flux is diminished and the aphelion cloud belt is present at equatorial latitudes. Clouds observed in the Supra-Horizon Movie data set also exhibit seasonality, with clouds predominantly observed during L_S = 72°-108°. The seasonal occurrence of clouds detected in the atmospheric movies is well correlated with orbital observations of water-ice clouds at similar times from the MCS and MARCI instruments on the MRO spacecraft. The observed clouds are tenuous and on average only make up a few-hundredths of an optical depth, although more opaque clouds are observed in some of the movies. Additionally, estimates of the phase function calculated using water-ice opacity retrievals from MCS are provided to show how Martian clouds scatter sunlight, and thus provide insight into the types of ice crystals that comprise the clouds.