GPS Event Calendar

"What drove the Lunar dynamo?"

Benjamin Weiss Professor of Planetary Sciences Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology

Abstract: Although the Moon today has no global magnetic field, paleomagnetic measurements of Apollo samples indicate the existence of an ancient field from at least 4.25 to 1.92 billion years ago. It has been proposed that the paleofield was generated by a core dynamo. However, the paleofield's apparent high intensity and longevity are major challenges to current theory. Three key difficulties have been that the paleofield intensity has been poorly constrained, while the paleofield's lifetime and direction have been essentially unknown. To address this, I describe three key new types of paleomagnetic measurements. First, enabled by our new controlled oxygen fugacity thermal demagnetization system, I report some of the first accurate lunar paleointensity measurements. Second, I present young paleointensities to constrain the end of the field's lifetime. Finally, I report a robust constraint on the field's paleodirection from Apollo 17 basalt flows (see photo below). The data collectively support the existence of an intense early dynamo powered by an unusually energetic mechanism like precession, followed by a weaker long-lived dynamo perhaps powered by core crystallization. The paleodirectional data are consistent with but do not require a Moon-centric axial dipole geometry like that of the Earth.

Members of the Ph.D. examining committee are: Jared Leadbetter (chair), Victoria Orphan (thesis adviser), Woody Fischer, George Rossman

Zoom link:

https://us04web.zoom.us/j/7372938281?pwd=dzNYZWdhdWNNV3JETHhhelpNaXQwdz09

Meeting ID: 737 293 8281