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Spiral features and the Coriolis Effect on Vesta's basin Rheasilvia

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  • Planetengeologie

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template for two-page abstracts in Word 97 (PC) SPIRAL FEATURES AND THE CORIOLIS EFFECT ON VESTA’S BASIN RHEASILVIA. K. Otto1, R. Jaumann1,2, K. Krohn1, K.-D. Matz 1, F. Preusker1, T. Roatsch1, F. Scholten1, I. Simon1, K.Stephan1, C. A. Ray- mond3 and C. T. Russell4, 1Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Planetary Research, Germany (Rutherfordstraße 2, 12489 Berlin, ([email protected]), 2Institute of Geosciences, Freie Universität Berlin, Germany, 3California Institute of Technology, Jet Propulsion Laboratory, Pasadena, USA, 4Institute of Geo- physics and Planetary Physics, University of California, Los Angeles, USA. Introduction: The Dawn space craft orbited as- teroid Vesta for one year arriving in August 2011 [1]. The on-board Framing Camera (FC) collected image data with a resolution up to 20 m/pixel [2]. Stereo im- ages from the High Altitude Mapping Orbit (HAMO, 60 m/pixel) were used to construct a Digital Terrain Model (DTM) of Vesta’s surface [3]. The FC images and the DTM revealed a large im- pact basin in the southern hemisphere, named Rheasil- via. Rheasilvia’s central peak located at 75°S and 301°E nearly coincides with Vesta’s south pole. Its diameter of about 500 km has the dimension of Vesta’s diameter (525 km) [2, 4]. This and Vesta’s relatively short rotation period of 5.3 hours indicate that the Cor- iolis force is likely to have an effect on mass motions within the Rheasilvia basin [5]. Indeed, a pervasive spiral deformation pattern has been observed [6]. Figure 1: Spiral pattern in Vesta’s southern hemi- sphere. Shown is a stereographic projection (equal angle) on a sphere of 255 km. The Coriolis Effect: The Coriolis force is a fic- tional force associated with rotating systems. The rota- tion deflects the motion perpendicular to the rotation axis to cause curved trajectories. The Coriolis force FC is given by where m is the mass of the moving body, Ω the angular velocity of the rotati

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