P2_3 Explaining Venus' Retrograde Rotation

Abstract

Venus is the only planet in the solar system that has a retrograde rotation. We investigated the idea of an asteroid colliding with a young Venus, that had a rotational period similar to Earth's, with enough kinetic energy to cause it to reverse direction. Taking the velocity of 2002 VE68 (a quasi-satellite of Venus), we found the required asteroid's mass to be 3.1x10^20 kg, comparable to that of Vesta.