Planetary Science Seminar fall-2015

Geomorphological evidence for ground ice on Ceres from lobate flows as seen by Dawn

Five decades of observations of Ceres’ albedo, surface composition, shape and density by Earth and space based telescopes suggest that Ceres is comprised of both silicates and several tens of percent water ice (McCord et al., 2010). Ceres’ bulk density of ~2100 kg/m3 (McCord and Sortin, 2005) and the detection of OH and water emissions from the Herschel Space Observatory (Küppers et al., 2014) all support this conclusion. From initial Dawn data we report geomorphological evidence for ground ice on Ceres in the form of ubiquitous flow features. The observed features exist on a morphological continuum between two endmembers: (1) thick, domical flows with well-developed snouts, and (2) thin, sheeted, multi-lobed flows with very long runouts. We interpret these features to be similar to ice-cored or ice-cemented flows, and ballistically emplaced fluidized ejecta respectively. A large population of morphologically intermediate flows also exists; they have been interpreted as being a mix of long-runout landslides and fluidized ejecta emplaced as surface flows.