Smooth pond-like deposits on asteroid 4 Vesta: Preliminary results from the Dawn mission

Abstract

Asteroid 4 Vesta is the second largest asteroid and is currently being investigated by the Dawn spacecraft. Vesta is of particular interest for our understanding of early solar system processes because it is most likely a fully differentiated planetesimal [1] that survived subsequent collisions and thus allows us to look back to the earliest phases of planet formation. Evidence for Vesta being differentiated comes from more than 900 HED (howardite-eucrite-diogenite) meteorites, which presumably originate from Vesta [e.g., 2-6]. Such a link between Vesta and the HED meteorites is supported by multispectral observations as well as dynamical considerations [7,8]. Launched in 2007, Dawn arrived at Vesta on July 16, 2011 to study the asteroid with three instruments, including the German Framing Camera (FC), the Italian Visible & Infrared Spectrometer (VIR), and the American Gamma Ray and Neutron Detector (GRaND). While there have been numerous observations from Earth and the Hubble space telescope [e.g., 9,10], Dawn provides the first high-resolution data from its survey orbit, high altitude mapping orbit (HAMO), and low altitude mapping orbit (LAMO). The inspection of FC data revealed smooth pond-like deposits of ambigious origin, similar to deposits on other asteroids such as Eros and Itokawa [11,12]. In principle, several scenarios for the origin of these deposits seem plausible and can be tested with Dawn data, including volcanism, impact sedimentation, impact melt deposition, dust levitation and transport, seismic shaking, or landslides.