A Photochemical PHO Network For Hydrogen-dominated Exoplanet Atmospheres
Due to the detection of phosphine PH3 in the Solar System gas giants Jupiter and Saturn, PH3 has long been suggested to be detectable in exosolar substellar atmospheres too. However, to date, a direct detection of phosphine has proven to be elusive in exoplanet atmosphere surveys.
We construct an updated phosphorus-hydrogen-oxygen (PHO) photochemical network suitable for simulation of gas giant hydrogen-dominated atmospheres. Using this network, we examine PHO photochemistry in hot Jupiter and warm Neptune exoplanet atmospheres at Solar and enriched metallicities. Our results show for HD 189733b-like hot Jupiters that HOPO, PO and P2 are typically the dominant P carriers at pressures important for transit and emission spectra, rather than PH3.
For GJ1214b-like warm Neptune atmospheres our results suggest that at Solar metallicity PH3 is dominant in the absence of photochemistry, but is generally not in high abundance for all other chemical environments. At 10 and 100 times Solar, small oxygenated phosphorus molecules such as HOPO and PO dominate for both thermochemical and photochemical simulations.
The network is able to reproduce well the observed PH3 abundances on Jupiter and Saturn. Despite progress in improving the accuracy of the PHO network, large portions of the reaction rate data remain with approximate, uncertain or missing values, which could change the conclusions of the current study
Elspeth K.H. Lee, Shang-Min Tsai, Julianne I. Moses, John M.C. Plane, Channon Visscher, Stephen J. Klippenstein
Comments: Submitted to ApJ (12 July 2024)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2409.06802 [astro-ph.EP] (or arXiv:2409.06802v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2409.06802
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Submission history
From: Elspeth Lee Dr
[v1] Tue, 10 Sep 2024 18:12:35 UTC (717 KB)
https://arxiv.org/abs/2409.06802
Astrobiology, Astrochemistry,
