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CATEGORIES:Bullard Laboratories Wednesday Seminars
SUMMARY:The last stage of Earth's formation: Increasing th
 e pressure - Simon Lock\, Harvard Univsersity
DTSTART;TZID=Europe/London:20171004T160000
DTEND;TZID=Europe/London:20171004T170000
UID:TALK80871AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/80871
DESCRIPTION:The final stage of terrestrial planet formation is
  marked by highly energetic collisions between pla
 netary sized bodies\, known as giant impacts. Gian
 t impacts melt and vaporize substantial fractions 
 of the colliding bodies and can leave the post-imp
 act body rapidly rotating. Some fraction of giant 
 impacts have sufficient energy and angular momentu
 m (AM) to produce a previously unrecognized planet
 ary object\, called a synestia. It has recently be
 en suggested that our Moon was formed from a synes
 tia created by the last giant impact in Earth’s ac
 cretion. I will demonstrate that the internal pres
 sures of Earth-like planets do not increase monoto
 nically during the giant impact stage\, but can va
 ry substantially in response to changes in rotatio
 n and thermal state. The internal pressures in an 
 impact-generated synestia are much lower than in a
  condensed\, slowly rotating planet of the same ma
 ss. For example\, the core-mantle boundary (CMB) p
 ressure can be as low as 60 GPa for a synestia wit
 h Earth mass and composition\, compared to 136 GPa
  in the present-day Earth. The lower pressures are
  due to the low density and rapid rotation of the 
 post-impact structure. After the formation of the 
 Moon from a synestia\, the internal pressures in t
 he interior of the synestia would have increased t
 o present-day Earth values in two stages: first by
  vapor condensation and second by removal of AM fr
 om the Earth during the tidal evolution of the Moo
 n. The pressure evolution of the Earth has several
  important implications for its structure and geoc
 hemistry\, which I will discuss.
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Lab
 s.
CONTACT:Sanne Cottaar
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