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SUMMARY:Magnetic microscopy of meteorites: probing the magnetic state of t
 he early solar system  - Professor Richard Harrison\, Department of Earth 
 Sciences
DTSTART:20180212T180000Z
DTEND:20180212T190000Z
UID:TALK78001@talks.cam.ac.uk
CONTACT:Beverley Larner
DESCRIPTION:Microstructural and geochemical studies of meteoritic metal ha
 ve been instrumental in shaping our current views of differentiated astero
 ids\, providing constraints on their cooling rate\, their size\, the timin
 g of their differentiation and their fractional crystallisation and impact
  histories. The characteristic Widmanstätten microstructure\, familiar to
  anyone who has looked at a polished and etched section of an iron meteori
 te with the naked eye\, hides a nanoscale complexity that is revealed only
  with high-resolution electron microscopy – a legacy of stranded diffusi
 on profiles\, metastability\, martensitic transformations\, chemical segre
 gation and ordering during slow cooling over millions of years on the pare
 nt body. The presence of soft bcc iron has traditionally lead to the meteo
 ritic metal being dismissed as a reliable carrier of paleomagnetic informa
 tion. However\, we have shown that\, under favourable circumstances\, pale
 omagnetic information can be recorded and retained on a local scale within
  a unique nanoscale intergrowth called the cloudy zone (CZ). High-resoluti
 on X-ray imaging methods enable the magnetic state of the CZ to be imaged 
 and analysed quantitatively\, opening up new avenues of research into the 
 nanopaleomagnetism of a range of meteorites. Such studies are not only rev
 ealing new insight into the thermochemical properties of asteroids in the 
 early solar system\, but provide us with unique opportunities to learn abo
 ut how magnetic fields are generated on planetary bodies in general\, and 
 the underlying physics of the dynamo generation process itself.
LOCATION:Bristol-Myers Squibb Lecture Theatre\, Department of Chemistry
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