Reorientation of Vesta: Gravity and tectonic predictions

Abstract

Vesta's large southern hemisphere impact basin is likely to have caused reorientation. However, because the basin is not centred at the south pole, Vesta likely also has a remnant rotational figure. Reorientation of 6 is predicted to have occurred based on the dimensions of the basin. Existing measurements of Vesta's shape are consistent with 20 or less reorientation, and 20% or less despinning. Both the remnant rotational figure and the basin contribute to the degree-2 gravity coefficients, which will be measured by the Dawn mission and will provide a test of the reorientation hypothesis. Reorientation and despinning also give rise to stresses. Vesta's stress state is likely to be dominated by isotropic contraction due to cooling (which does not affect the gravity coefficients). However, the orientation of the resulting thrust features will be controlled by the amount of reorientation and despinning, providing another observational test. Copyright 2011 by the American Geophysical Union.