Colloquium: Roger Phillips

Institute Scientist, Southwest Research Institute, Boulder, CO. At WUSTL: Director Emeritus, MCSS; Professor Emeritus, E&PS

Abstract: Around the time of this colloquium, having used the very last drop of propellant, the MESSENGER spacecraft will have crashed (or will be about to crash, or will crash while I am talking) onto the surface of Mercury, ending a spectacular run of four years in orbit. Images of Mercury’s surface obtained in the 1970s by the Mariner 10 spacecraft revealed a lunar-like landscape but with the addition of compressional tectonic features, undoubtedly the result of a cooling interval of Mercury’s massive iron core. From MESSENGER, we have learned that Mercury is vastly different from the Moon and every other place that we know about. This talk will be geophysics-centric (no surprise) and will address some basic questions, including: (i) What is the long-wavelength shape of Mercury, how does it compare to the Moon, and what in blazes has been supporting its non-hydrostatic shape for the last 4+billion years? (ii) How much planetary contraction has actually gone on, and what does this look like at the surface? (iii) What is the thermal history of Mercury and how is it constrained by the (very recently discovered) presence of crustal remanent magnetic fields and by Mercury’s magmatic history?