The geology of the occator quadrangle of dwarf planet Ceres: Floor-fractured craters and other geomorphic evidence of cryomagmatism

The Dawn Science Team is conducting a geological mapping campaign at Ceres during the nominal mission, including iterative mapping using data obtained during each orbital phase. We are using geological mapping as a method to identify the geologic processes that have modified the surface of dwarf planet Ceres. We here present the geology of the Ac-9 Occator quadrangle, located between 22˚S-22˚N and 216-288˚E. The Ac-9 map area is within the topographically high region named Hanami Planum. Features of note within the profile include impact craters Occator, Azacca, Lociyo, Nepen and Kirnis. Four of these craters have fractured, shallow floors, morphometrically comparable to floor-fractured craters (FFCs) on the Moon. Similar to models for the formation of the lunar FFCs, we suggest that these Ceres FFCs are a result of cryomagmatic uplift under the crater floors. A set of regional linear structures called the Samhain Catenae do not have any obvious relationship to impact craters. Many of the catenae are comprised of smaller structures that have linked together, suggestive of en echelon fractures. It has been suggested that these fractures formed due to the uplift of Hanami Planum due to cryromagmatic plumes.