The Impact of Cometary 'impacts' on the Chemistry, Climate, and Spectra of Hot Jupiter Atmospheres
The Astrophysical Journal(2024)
摘要
Impacts from icy and rocky bodies have helped shape the composition of solar
system objects, for example the Earth-Moon system, or the recent impact of
comet Shoemaker-Levy 9 with Jupiter. It is likely that such impacts also shape
the composition of exoplanetary systems. Here we investigate how cometary
impacts might affect the atmospheric composition/chemistry of hot Jupiters,
which are prime targets for characterisation. We introduce a parametrised
cometary impact model that includes thermal ablation and pressure driven
breakup, which we couple with the 1D `radiative-convective' atmospheric model
ATMO, including disequilibrium chemistry. We use this model to investigate a
wide range of impactor masses and compositions, including those based on
observations of Solar System comets, and interstellar ices (with JWST). We find
that even a small impactor (R = 2.5 km) can lead to significant short-term
changes in the atmospheric chemistry, including a factor >10 enhancement in
H_2O, CO, CO_2 abundances, and atmospheric opacity more generally, and the
near complete removal of observable hydrocarbons, such as CH_4, from the
upper atmosphere. These effects scale with the change in atmospheric C/O ratio
and metallicity. Potentially observable changes are possible for a body that
has undergone significant/continuous bombardment, such that the global
atmospheric chemistry has been impacted. Our works reveals that cometary
impacts can significantly alter or pollute the atmospheric
composition/chemistry of hot Jupiters. These changes have the potential to
mute/break the proposed link between atmospheric C/O ratio and planet formation
location relative to key snowlines in the natal protoplanetary disc.
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关键词
Exoplanet atmospheres,Atmospheric composition,Exoplanet atmospheric composition,Astrochemistry,Computational astronomy,Comets
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