Geological Society of America

T152 The Geology of Asteroid 4 Vesta as Seen by Dawn: Results from One Year in Orbit

Tuesday, 6 November 2012
8:00 AM - 12:00 PM
213D

THE GEOLOGY OF VESTA: AN OVERVIEW

Paper number: T152-3
Program: Technical Sessions
Time: 8:40 AM – 9:00 AM

Authors

R. Jaumann Presenting Author
Institute of Planetary Research, Berlin
David T. Blewett
Johns Hopkins University Applied Physics Laboratory, Laurel, MD
Christopher T. Russell
University of California, Los Angeles, Los Angeles, CA
Carol A. Raymond
California Institute of Technology, Pasadena, CA
Carle M. Pieters
Brown University, Providence, RI
R. Aileen Yingst
University of Wisconsin-Green Bay, Green Bay, WI
David Williams
Arizona State University, Tempe, AZ
Debra L. Buczkowski
Johns Hopkins Applied Physics Laboratory, Laurel, MD
Katrin Krohn
German Aerospace Center (DLR), Berlin
W. Brent Garry
Planetary Science Institute, Tucson, AZ

Abstract

The Dawn spacecraft collected over 28,000 images and a wealth of spectral data of Vesta’s surface. These data enable analysis of Vesta’s diverse geology including impact craters of all sizes and unusual shapes, a variety of ejecta blankets, large troughs, impact basins, enigmatic dark material, and considerable evidence for mass wasting and surface alteration processes (1). Two large impact basins, Veneneia underlying the larger Rheasilvia basin dominate the south polar region (1, 2). The depression surrounding Vesta’s south pole was formed by two giant impacts one billion and two billion years ago (2, 3). Vesta’s global tectonic patterns (two distinct sets of large troughs orthogonal to the axes of the impacts) strongly correlate with the locations of the two south polar impact basins, and were likely created by their formation (1, 4). Numerous unusual asymmetric impact craters and ejecta indicate the strong influence of topographic slope in cratering on Vesta (1). Very steep topographic slopes near to the angle of repose are common; slope failures make resurfacing due to impacts and their associated gravitational slumping and seismic effects an important geologic process on Vesta (1). Clusters of pits in combination with impact melt (5) suggest the presence of volatile materials underlying that melt in some crater floors. Relatively dark material of uncertain origin is intermixed in the regolith layers and partially excavated by younger impacts yielding dark outcrops, rays and ejecta (1, 6). Vesta’s surface is reworked by intense impacts and thus much younger than the formation of its crust (3).

(1) Jaumann, et al., 2012, Science 336, 687-690; (2) Schenk et al., 2012, Science 336, 964-967; (3) Marchi, et al., 2012, Science 336, 690-694; (4) Buczkowski, et al., 2012, GRL, submitted; (5) Denevi, et al., 2012, Science, in review; (6) McCord, et al., 202, Nature, in review.

Acknowledgment: We thank the Dawn Science and Operations Team, particularly E. Ammannito, U. Carsenty, B. Denevi, C. M. DeSanctis, D. Elbeshausen, H. Hiesinger, S. Joy, H.U. Keller, E. Kersten, T. Kneissl, K. Krohn, S. Marchi, K.D. Matz, T. McCord, S. Mest, H. McSween, S. Mottola, A. Nathues, G. Neukum, D. O’Brien, K. Otto, C. Polanskey, F. Preusker, M. Rayman, T. Roatsch, P. Schenk, N. Schmedemann, J. Scully, K. Stephan, M. Sykes, M. Zuber.