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SUMMARY:Greedy icy planets\, or How Uranus and Neptune enrich their atmosp
 heres in carbon by core accretion in the debris disc phase - Paul Huet (Pa
 ris Observatory)
DTSTART:20250311T130000Z
DTEND:20250311T140000Z
UID:TALK227275@talks.cam.ac.uk
CONTACT:Dr Dolev Bashi
DESCRIPTION:Observations of gas in exo-Kuiper belts (mostly CO) suggest it
  may be common in young planetary systems\, potentially reshaping our unde
 rstanding of the Solar System’s youth. Uranus and Neptune’s high atmos
 pheric C/H ratios (60–80× protosolar) could trace late accretion of car
 bon-rich gas from a primordial Kuiper belt. We model gas release and visco
 us evolution in a Solar System-analog belt\, quantifying gas capture by th
 e ice giants. Using a disk model with varied initial masses (up to 50 M⊕
 )\, viscosities\, and accretion efficiencies\, we simulate CO release and 
 planetary enrichment. Results show a massive belt (∼50 M⊕\, similar to
  that considered in e.g. the Nice model) can supply sufficient CO via late
  accretion to explain observed C/H values. While solid accretion during fo
 rmation contributes to carbon enrichment\, we find that an additional late
  accretion may be needed to explain the very high super solar values\, whi
 ch aligns with gas capture from a young\, gaseous Kuiper belt. This mechan
 ism may be universal\, influencing metallicity in exoplanetary giants\, wi
 th observational implications for sub-Jupiter exoplanets. Our findings sup
 port a once-gas-rich Kuiper belt as a key driver of ice giant atmospheric 
 evolution.
LOCATION:Hoyle Committee Room - Details to be sent by email
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