Paper No. 3
Presentation Time: 8:40 AM

THE GEOLOGY OF VESTA: AN OVERVIEW (Invited Presentation)


JAUMANN, R., German Aerospace Center (DLR) Berlin, Institute of Planetary Research, Rutherfordstrasse 2, Berlin, D-12489, Germany, RUSSELL, Christopher T., Institute of Geophysics, University of California, Los Angeles, 603 Charles Young Drive, 3845, Los Angeles, CA 90095, RAYMOND, Carol A., Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, PIETERS, Carle M., Earth, Environmental, and Planetery Sciences, Brown University, Box 1846, Providence, RI 02912, YINGST, R. Aileen, Natural and Applied Sciences, University of Wisconsin-Green Bay, 2420 Nicolet Dr, University of Wisconsin - Green Bay, Green Bay, WI 54311, WILLIAMS, David A., School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, BUCZKOWSKI, Debra L., Space Departrment, Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723, KROHN, Katrin, Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstr. 2, Berlin, 12489, Germany, GARRY, W. Brent, Planetary Science Institute, 1700 E. Ft. Lowell, Suite 106, Tucson, AZ 85719 and BLEWETT, David T., Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, ralf.jaumann@dlr.de

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.