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SUMMARY:The Lunar Dynamo and the Solar Nebula Magnetic Field (Keynote spea
 ker) - Benjamin Weiss (Massachusetts Institute of Technology)
DTSTART:20220915T080000Z
DTEND:20220915T090000Z
UID:TALK177497@talks.cam.ac.uk
DESCRIPTION:\n\n\n\nIn this two-part talk\, I review how key unsolved prob
 lems in our understanding of the magnetism of the ancient moon and solar n
 ebula can be addressed with paleomagnetic measurements.\nRemanent magnetiz
 ation in lunar rocks has long been hypothesized to be the product of a cor
 e dynamo. However\, the paleofield&rsquo\;s apparent high intensity and lo
 ngevity are major challenges to current theory. Two key difficulties are t
 hat the paleofield&rsquo\;s intensity has been poorly constrained and its 
 direction has been essentially unknown. I describe three key new types of 
 ongoing paleomagnetic measurements that address these issues. First\, cont
 rolled atmosphere thermal demagnetization is enabling some of the first ac
 curate lunar paleointensity measurements. Second\, paleointensities are be
 ing measured for young samples to constrain the field&rsquo\;s lifetime. F
 inally\, constraints on the field&rsquo\;s paleodirection are being derive
 d from bedrock samples. The data collectively support the existence of an 
 early (>~3.5 Ga) dynamo with a fluctuating intensity\, perhaps powered by 
 an unusually energetic mechanism like precession\, followed by a weaker lo
 ng-lived dynamo perhaps powered by core crystallization. The paleodirectio
 nal data are consistent with but do not require a Moon-centric axial dipol
 e geometry like that of the Earth.\nA key stage in planet formation is the
  evolution of a gaseous and magnetized solar nebula. However\, the intensi
 ty and lifetime of the nebular field and the history of mass transport in 
 the early solar system have been poorly constrained. Here we present analy
 ses of the remanent magnetization in meteorites demonstrating that an appr
 oximately Earth-strength nebular magnetic field existed throughout the inn
 er solar system (\n\n\n\n
LOCATION:Seminar Room 1\, Newton Institute
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