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SUMMARY:Exocomets and their effect on inner planet atmospheres - Prof. Mar
 k Wyatt (IoA\, Cambridge)
DTSTART:20181112T140000Z
DTEND:20181112T150000Z
UID:TALK109921@talks.cam.ac.uk
CONTACT:Dr William Béthune
DESCRIPTION:It is known that ~20% of nearby stars host planetesimal belts 
 orbiting 10s of au from the star. For a growing number CO gas has been det
 ected coincident with the planetesimal belts showing that their planetesim
 als have a similar composition to Solar System comets. It is expected that
  some of these planetesimals may be perturbed into the inner regions of th
 e system where they may collide with any planets residing there. The hot d
 ust seen in several systems may be evidence of such comet-like dynamics\, 
 and in one system this picture is reinforced by the detection of CO close 
 to the CO2 sublimation radius. This seminar will consider the effect of co
 llisions with such an exocomet population on the atmospheres of inner plan
 ets. These atmospheres can be stripped in collisions\, but can also be enh
 anced by the delivery of volatiles\, in a way that can be quantified from 
 simulations of impacts. It will be shown that whether an atmosphere grows 
 or depletes can be inferred from the planet’s mass and semimajor axis (f
 or given assumptions about the cometary impactors). While application to t
 he Solar System terrestrial planets highlights the sensitivity of conclusi
 ons to the model assumptions (e.g.\, since the Earth lies close to the gro
 wth/depletion boundary)\, application to extrasolar planetary systems show
 s that broad trends are more robust\, such as the depletion of the atmosph
 eres of close-in exoplanets like those of TRAPPIST-1\, and the growth of t
 hose at larger separation.
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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