Issue |
A&A
Volume 693, January 2025
|
|
---|---|---|
Article Number | A132 | |
Number of page(s) | 10 | |
Section | Planets, planetary systems, and small bodies | |
DOI | https://doi.org/10.1051/0004-6361/202450598 | |
Published online | 10 January 2025 |
A new pathway to SO2
Revealing the NUV driven sulfur chemistry in hot gas giants
1
Anton Pannekoek Institute for Astronomy, University of Amsterdam,
1090GE
Amsterdam,
The Netherlands
2
Department of Earth and Planetary Sciences, University of California,
Riverside,
CA,
USA
3
SRON Netherlands Institute for Space Research,
Niels Bohrweg 4,
2333
CA
Leiden,
The Netherlands
4
Department of Astrophysics/IMAPP, Radboud University Nijmegen,
PO Box 9010,
6500
GL
Nijmegen,
The Netherlands
5
Institute of Astronomy, KU Leuven,
Celestijnenlaan 200D,
3001
Leuven,
Belgium
★ Corresponding author; wiebedg@gmail.com
Received:
3
May
2024
Accepted:
4
November
2024
Context. Photochemistry is a key process that drives planetary atmospheres away from local thermodynamic equilibrium. Recent observations of the H2 dominated atmospheres of hot gas giants have detected SO2 as one of the major products of this process.
Aims. We investigated which chemical pathways lead to the formation of SO2 in an atmosphere, and we investigated which part of the flux from the host star is necessary to initiate SO2 production.
Methods. We used the publicly available S–N–C–H–O photochemical network in the VULCAN chemical kinetics code to compute the disequilibrium chemistry of an exoplanetary atmosphere.
Results. We find that there are two distinct chemical pathways that lead to the formation of SO2. The formation of SO2 at higher pressures is initiated by stellar flux >200 nm, whereas the formation of SO2 at lower pressures is initiated by stellar flux <200 nm. In deeper layers of the atmosphere, OH is provided by the hydrogen abstraction of H2O, and sulfur is provided by the photodissociation of SH and S2, which leads to a positive feedback cycle that liberates sulfur from the stable H2S molecule. In the upper layers of the atmosphere, OH is provided by the photodissociation of H2O, and sulfur can be liberated from H2S either by the photodissociation of SH and S2, or by the hydrogen abstraction of SH.
Conclusions. We conclude that the stellar flux in the 200–350 nm wavelength range as well as the ratio of near-UV to UV radiation are important parameters determining the observability of SO2. In addition, we find that there is a diversity of chemical pathways to the formation of SO2. This is crucial for the interpretation of SO2 detections and derived elemental abundance ratios, and for overall metallicities.
Key words: planets and satellites: atmospheres / planets and satellites: composition / planets and satellites: gaseous planets / planet–star interactions
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.