THE GEOLOGIC MAPPING OF SMALL BODIES: EXPERIENCE FROM NASA’S DAWN MISSION

NASA’s Dawn spacecraft orbited the two most massive objects in the Main Asteroid Belt (MAB), the asteroid (4) Vesta and the dwarf planet (1) Ceres, between 2011 and 2016. The Dawn Science Team conducted geological mapping campaigns during the nominal missions at each of these objects, with the goals of providing real time interpretations of geological features and providing geological context for compositional measurements made by the Visible and Infrared Spectrometer and the Gamma-Ray and Neutron Detector. These geological mapping campaigns produced both lower-resolution global geologic maps and higher resolution regional quadrangle maps for each object, with the additional goal of identifying the chronostratigraphy and developing a geologic time scale for both Vesta and Ceres. This presentation will discuss both the challenges of conducting geologic mapping on small bodies, and making geologic maps from a science team during an active planetary mission. Vesta’s and Ceres’ geologic histories are very different, resulting from their different compositions and different interactions with other objects in the MAB. Whereas the rocky Vesta has a surface that was strongly affected by two large impacts at its south pole, Veneneia and Rheasilvia, that produced global ridge-&-trough systems, Ceres surface shows little evidence for similarly large impacts. Rather, surface modification by many smaller impacts, mass wasting, ground ice flow, and cryovolcanism within an ice-bearing crust has dominated its geologic evolution.

Support by the Dawn Instrument, Operations, and Science Teams is grateful acknowledged. This work is supported by grants from NASA through the Dawn project, and from the German and Italian Space Agencies.