Physical Society Colloquium

The Long-Term Rotational Stability of Terrestrial Planets

Jerry Mitrovica

Department of Physics
University of Toronto

Following the classic work of Tommy Gold in the 1950s, studies of the long-term evolution of terrestrial (i.e., rocky) planets generally assume that these planets are rotationally unstable. That is, a load of arbitrary size, even as small as Gold's “beetle”, will drive a motion of the rotation pole relative to the surface geography (or true polar wander,TPW) that will ultimately move the load to the equator. I'll demonstrate that a correct physical treatment of the outer “lithospheric” shell of the planet introduces a strong stabilization of the rotation axis. Moreover, I'll show how this stabilization has recently resolved debates concerning long-term TPW and modern climate change on Earth, as well as the existence of ancient oceans on Mars.