Initial Geologic Mapping of the AC-H-8 Nawish Quadrangle of Ceres using DAWN Spacecraft Data

Abstract

Herein we present the geologic mapping of the Ac-H-8 Nawish Quadrangle of Ceres, in order to identify the geologic processes that have modified the surface of dwarf planet Ceres, which NASA’s Dawn spacecraft began orbiting in April 2015. Framing Camera data from the Approach (1.3 km/px) and Survey (415 m/px) orbits, including grayscale and color images and digital terrain models derived from stereo images, have enabled an initial characterization of the surface. Ceres has been divided into 15 quadrangles, and this abstract discusses the geology of the Ac-H-8 Nawish Quadrangle, located between -22-22˚ and 144-216˚E. The quadrangle's name comes from the 75 km diameter crater Nawish which is located in the northern sector of the quadrangle. Nawish crater has a 3 km diameter central peak composed by a very bright material. This very bright material is being mapped elsewhere in the quadrangle in association with crater-related structures as rims or ejecta field. The western part of the quadrangle shows a ‘smooth material’ that hosts a significantly lower impact crater density than most of the rest of Ceres’ surface. This smooth material extends beyond Nawish to the west, and a key goal of ongoing mapping will be to determine the possible resurfacing processes that formed this unit. Another primary feature of the study area is an unamed, partially degraded, 100-km crater in the central bottom sector of the quadrangle. The topography of the quadrangle obtained from stereo-processing of imagery, shows an highland in the middle of the quadrangle. The topography is lower in the northern and southern borders of the quadrangle, with an altitude range of about 9500 meters. Future work will include more detailed definition and characterization of surface units and estimates of their compositional variations through study of color images and Visible and Infrared spectrometer data, and application of crater statistical techniques to obtain model ages of surface units.