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SUMMARY:Forming planetary cores without magma oceans: an alternative view 
 from in-situ tomographic imaging at extreme conditions - Dr Geoff Bromiley
  - University of Edinburgh
DTSTART:20181015T163000Z
DTEND:20181015T173000Z
UID:TALK109879@talks.cam.ac.uk
CONTACT:Ben Johnson
DESCRIPTION:Magma oceans are used to explain many processes in the early s
 olar system\, from efficient silicate-\nmetal differentiation in terrestri
 al planets to formation of the Moon’s flotation crust\, and from\ndevelo
 pment of deep compositional heterogeneities in the Earth to efficient mant
 le degassing and\nformation of a hydrosphere and atmosphere. It is commonl
 y assumed that a substantial portion of\nthe Earth was melted multiple tim
 es during accretion: at least one deep\, early magma ocean which\nkick-sta
 rted efficient core formation\, and a later stage of melting during the Mo
 on-forming event.\nChemical exchange between metal and silicate during the
 se magma ocean episodes may have\ncontrolled the composition of the silica
 te portion of Earth. However\, recent work casts doubt on the\nidea that m
 antle chemistry can be modelled based on silicate-metal equilibration in a
  deep magma\nocean. There is also growing evidence that core segregation b
 egan very early in the inner solar\nsystem\, and in smaller bodies for whi
 ch magma oceans are harder to invoke.\n\n\nIn this talk\, I will summarise
  evidence for an alternative mechanism for core formation: lower\ntemperat
 ure percolation of core-forming liquids through solid silicate. Recent adv
 ances in in-situ\nmicrotomographic imagining allow us to study complex pro
 cesses such as core formation directly\nunder deep planetary conditions. B
 y studying textural development in complex systems in real time\,\nwe can 
 constrain\, for the first time\, rates of melt segregation. This allows us
  to test the efficiency of\npercolation as a mechanism for core formation\
 , and to consider the influence that this process might\nhave had on the c
 omposition of the Earth. As well as introducing current and future develop
 ments\nwithin the exciting field of ‘extreme conditions microtomography
 ’ I will also discuss the wider\nimplications that this work has on our 
 understanding of planetary geochemistry\, and the\nmechanisms of core form
 ation and segregation in rocky planets.
LOCATION: Harker 1\, Department of Earth Sciences\, Downing Street
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