Planetary and Space Science

Planetary and Space Science

8 Pages · 2013 · 3.23 MB · English

Small crater populations on Vesta S. Marchia,f,n, W.F. Bottkea, D.P. O'Brienb, P. Schenkc, S. Mottolad, M.C. De Sanctise, D.A. Kringf, D.A. Williamsg, C.A. Raymondh

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Small crater populations on Vesta S. Marchi a,f, n, W.F. Bottke a, D.P. O'Brien b, P. Schenk c, S. Mottola d, M.C. De Sanctis e, D.A. Kring f, D.A. Williams g, C.A. Raymond h, C.T. Russell i aNASA Lunar Science Institute, Southwest Research Institute, Boulder, CO, USAbPlanetary Science Institute, Tucson, AZ, USAcLunar and Planetary Institute, Houston, TX, USAdInstitut für Planetenforschung, DLR-Berlin, GermanyeIstituto Nazionale d'Astrofisica, Roma, ItalyfNASA Lunar Science Institute, USRA—Lunar and Planetary Institute, Houston, TX, USAgArizona State University, Tempe, AZ, USAhJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USAiUniversity of California, Los Angeles, CA, USA article info Article history: Received 18 December 2012 Received in revised form 30 April 2013 Accepted 3 May 2013 Keywords: Asteroid (4) Vesta Asteroid cratering Asteroid evolution Main belt asteroids abstract The NASA Dawn mission has extensively examined the surface of asteroid Vesta, the second most massive body in the main belt. The high quality of the gathered data provides us with a unique opportunity to determine the surface and internal properties of one of the most important and intriguing main belt asteroids (MBAs). In this paper, we focus on the size frequency distributions (SFDs) of sub-kilometer impact craters observed at high spatial resolution on several selected young terrains on Vesta. These small crater populations offer an excellent opportunity to determine the nature of their asteroidal precursors (namely MBAs) at sizes that are not directly observable from ground-based telescopes (i.e., below∼100 m diameter). Moreover, unlike many other MBA surfaces observed by spacecraft thus far, the young terrains examined had crater spatial densities that were far from empirical saturation. Overall, wefind that the cumulative power- law index (slope) of small crater SFDs on Vesta is fairly consistent with predictions derived from current collisional and dynamical models down to a projectile size of∼10 m diameter (e.g.,Bottke et al., 2005a,b). TheshapeoftheimpactorSFDforsmallprojectilesizesdoesnotappeartohavechangedoverthelastseveral billions of years, and an argument can be made that the absolute number of small MBAs has remained roughly constant (within a factor of 2) over the same time period. The apparent steady state nature of the main

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