Unless noted, all listed events are open to the general public.
Wednesday Seminar in Geology: GEL 190/290
Seminars are scheduled for Wednesday afternoon at 4:00 PM. Additional optional seminars that may be included as part of the Geology 190 series may be scheduled at other times.
Friday Lunch Talk: "A Geology tradition since the Phanerozoic!"
Fridays at noon. Students and faculty give informal lectures on research, travel, or other interests.
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Wednesday, May 25th, 2022
Wednesday Seminar | 4:10 PM, 55 Roessler
History of the solar nebula from meteorite paleomagnetism -- by Ben Weiss, Massachusetts Institute of Technology
A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the intensity of the nebular field, the lifetime of the nebula, and the history of mass transport in the early solar system have been poorly constrained. Here we present analyses of the remanent magnetization in meteorites demonstrating that an approximately Earth-strength nebular magnetic field existed throughout the inner solar system (<7 AU) during the first 1-3 My after solar system formation. This supports the hypothesis that a nebular magnetic field played a fundamental role in mass and angular momentum transport in the disk. The solar system field then declined to near-zero by ~4 My after solar system formation, indicating that the solar nebula had dispersed by this time. This sets the timescale for formation of the gas giants and disk-driven planet migration and supports the hypothesis that giant planets form by a two-stage process involving formation of a rock-ice core followed by runaway gas accretion. Finally, our recent measurements of that two unusually volatile-rich carbonaceous meteorites find that they record weak field conditions during the lifetime of the nebula, suggesting that their materials formed at ~10-30 AU from the early Sun. This provides evidence for large-scale dynamical mixing of solids in the solar system and indicates that we may have rock samples from the proto-Kuiper belt.