A patchy CO<sub>2</sub> exosphere on Ganymede revealed by the <i>James Webb</i> Space Telescope
Jupiter’s icy moon Ganymede has a tenuous exosphere produced by sputtering and possibly sublimation of water ice. To date, only atomic hydrogen and oxygen have been directly detected in this exosphere. Here, we present observations of Ganymede’s CO 2 exosphere obtained with the James Webb Space Telescope. CO 2 gas is observed over different terrain types, mainly over those exposed to intense Jovian plasma irradiation, as well as over some bright or dark terrains. Despite warm surface temperatures, the CO 2 abundance over equatorial subsolar regions is low. CO 2 vapor has the highest abundance over the north polar cap of the leading hemisphere, reaching a surface pressure of 1 pbar. From modeling we show that the local enhancement observed near 12 h local time in this region can be explained by the presence of cold traps enabling CO 2 adsorption. However, whether the release mechanism in this high-latitude region is sputtering or sublimation remains unclear. The north polar cap of the leading hemisphere also has unique surface-ice properties, probably linked to the presence of the large atmospheric CO 2 excess over this region. These CO 2 molecules might have been initially released in the atmosphere after the radiolysis of CO 2 precursors, or from the sputtering of CO 2 embedded in the H 2 O ice bedrock. Dark terrains (regiones), more widespread on the north versus south polar regions, possibly harbor CO 2 precursors. CO 2 molecules would then be redistributed via cold trapping on ice-rich terrains of the polar cap and be diurnally released and redeposited on these terrains. Ganymede’s CO 2 exosphere highlights the complexity of surface-atmosphere interactions on Jupiter’s icy Galilean moons.
Authors
- Zachariah Milby (ORCID: https://orcid.org/0000-0001-5683-0095)
- A. Mura (ORCID: https://orcid.org/0000-0002-4552-4292)
- Joachim Saur (ORCID: https://orcid.org/0000-0003-1413-1231)
- Samantha K. Trumbo (ORCID: https://orcid.org/0000-0002-0767-8901)
- Olivier Poch (ORCID: https://orcid.org/0000-0002-7134-3217)
- В. Е. Захаров (ORCID: https://orcid.org/0000-0001-8855-7185)
- F. Tosi (ORCID: https://orcid.org/0000-0003-4002-2434)
- Adrien Masson (ORCID: https://orcid.org/0000-0002-2250-941X)
- Michael E. Brown (ORCID: https://orcid.org/0000-0002-8255-0545)
- Lorenz Roth (ORCID: https://orcid.org/0000-0003-0554-4691)
- Thierry Fouchet (ORCID: https://orcid.org/0000-0001-9040-8285)
- Katherine de Kleer (ORCID: https://orcid.org/0000-0002-9068-3428)
- Stefan Duling (ORCID: https://orcid.org/0000-0001-7220-9610)
- Pablo Rodríguez‐Ovalle (ORCID: https://orcid.org/0000-0003-2594-2128)
- B. Schmitt (ORCID: https://orcid.org/0000-0002-1230-6627)
- É. Quirico (ORCID: https://orcid.org/0000-0003-2768-0694)
- P. M. Fry (ORCID: https://orcid.org/0000-0002-7367-6541)
- D. Bockelée–Morvan (ORCID: https://orcid.org/0000-0002-8130-0974)
- Imke de Pater (ORCID: https://orcid.org/0000-0002-4278-3168)
- Richard Cartwright (ORCID: https://orcid.org/0000-0002-6886-6009)
- François Leblanc (ORCID: https://orcid.org/0000-0002-5548-3519)
- Audrey Moingeon
- Emmanuel Lellouch
- St'ephanie Cazaux
- S. Glenn Orton
- F. Merlin
- N. Leigh Fletcher
- H. Michael Wong
Institutions
- California Institute of Technology (US)
- Centre National de la Recherche Scientifique (FR)
- Planetary Science Institute (US)
- Jet Propulsion Laboratory (US)
- University of Wisconsin–Madison (US)
- University of Leicester (GB)
- University of Cologne (DE)
- Université de Versailles Saint-Quentin-en-Yvelines (FR)
- Université Paris Cité (FR)
- Université Paris Sciences et Lettres (FR)
- Johns Hopkins University Applied Physics Laboratory (US)
- University of California San Diego (US)
- Sorbonne Université (FR)
- Sorbonne Paris Cité (FR)
- Institute for Space Astrophysics and Planetology (IT)
- Laboratoire d’études spatiales et d’instrumentation en astrophysique (FR)
- Laboratoire atmosphères, milieux, observations spatiales (FR)
- KTH Royal Institute of Technology (SE)
- Université Grenoble Alpes (FR)
- University of California, Berkeley (US)
- Delft University of Technology (NL)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2024-09-27
- DOI
- https://doi.org/10.1051/0004-6361/202451599
- Citations
- 6
- Primary Topic
- Astro and Planetary Science
- Type
- article
- Field-Weighted Citation Impact
- 1.99
Funders
- Agence Nationale de la Recherche
- Science and Technology Facilities Council