The CH₄ abundance in Jupiter's upper atmosphere

A. Sánchez-López , M. López-Puertas , M. García-Comas , B. Funke , T. Fouchet (1) , I. A. G. Snellen

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics

Hydrocarbon species, and in particular CH₄, play a key role in the stratosphere-thermosphere boundary of Jupiter, which occurs around the μ-bar pressure level. Previous analyses of solar occultation, He and Ly-α airglow, and ISO/SWS measurements of the radiance around 3.3 μm have inferred significantly different methane concentrations. Here we aim to accurately model the CH₄ radiance at 3.3 μm measured by ISO/SWS by using a comprehensive non-local thermodynamic equilibrium model and the most recent collisional rates measured in the laboratory for CH₄ to shed new light onto the methane concentration in the upper atmosphere of Jupiter. These emission bands have been shown to present a peak contribution precisely at the μ-bar level, hence directly probing the region of interest. We find that a high CH₄ concentration is necessary to explain the data, in contrast with the most recent analyses, and that the observations favour the lower limit of the latest laboratory measurements of the CH₄ collisional relaxation rates. Our results provide precise constraints on the composition and dynamics of the lower atmosphere of Jupiter.

Mots clés: planets and satellites: atmospheres; methods: data analysis - techniques: spectroscopic; planets and satellites: individual: Jupiter; Astrophysics - Earth and Planetary Astrophysics; planets and satellites: atmospheres

Domaines: Planète et Univers [physics]; Astrophysique [astro-ph]

A. Sánchez-López, M. López-Puertas, M. García-Comas, B. Funke, T. Fouchet, et al.. The CH₄ abundance in Jupiter's upper atmosphere. Astronomy and Astrophysics - A&A, 2022, 662, ⟨10.1051/0004-6361/202141933⟩. ⟨insu-03713301⟩