The Atmosphere of Titan in Late Northern Summer from JWST and Keck Observations

Saturn’s moon Titan undergoes a long annual cycle of 29.45 Earth years. Titan’s northern winter and spring were investigated in detail by the Cassini-Huygens spacecraft (2004-2017), but the northern summer season remains sparsely studied.

Here we present new observations from the James Webb Space Telescope (JWST) and Keck II telescope made in 2022 and 2023 during Titan’s late northern summer. Using JWST’s mid-infrared instrument, we spectroscopically detected the methyl radical, the primary product of methane break-up and key to the formation of ethane and heavier molecules.

Using the near-infrared spectrograph onboard JWST, we detected several non-local thermodynamic equilibrium CO and CO₂ emission bands, which allowed us to measure these species over a wide altitude range.

Lastly, using the near-infrared camera onboard JWST and Keck II, we imaged northern hemisphere tropospheric clouds evolving in altitude, which provided new insights and constraints on seasonal convection patterns. These observations pave the way for new observations and modelling of Titan’s climate and meteorology as it progresses through the northern fall equinox, when its atmosphere is expected to show notable seasonal changes.

Seasons on Titan seen by various spacecraft missions. Extended observations by Cassini (June 2004 to September 2017) may be compared to JWST (from November 2022). The early JWST observations probe a significantly different season to Cassini (late northern summer), last seen in the early 1990s. — astro-ph.EP

Conor A. Nixon, Bruno Bézard, Thomas Cornet, Brandon Park Coy, Imke de Pater, Maël Es-Sayeh, Heidi B. Hammel, Emmanuel Lellouch, Nicholas A. Lombardo, Manuel López-Puertas, Juan M. Lora, Pascal Rannou, Sébastien Rodriguez, Nicholas A. Teanby, Elizabeth P. Turtle, Richard K. Achterberg, Carlos Alvarez, Ashley G. Davies, Katherine de Kleer, Greg Doppmann, Leigh N. Fletcher, Alexander G. Hayes, Bryan J. Holler, Patrick G. J. Irwin, Carolyn Jordan, Oliver R. T. King, Nicholas W. Kutsop, Theresa C. Marlin, Henrik Melin, Stefanie N. Milam, Edward M. Molter, Luke Moore, Yaniss Nyffenegger-Péré, James O’Donoghue, John O’Meara, Scot C. R. Rafkin, Michael T. Roman, Arina Rostopchina, Naomi Rowe-Gurney, Carl Schmidt, Judy Schmidt, Christophe Sotin, Tom S. Stallard, John A. Stansberry, Robert A. West

Comments: 41 pages, 12 figures, 1 table
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2505.10655 [astro-ph.EP] (or arXiv:2505.10655v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2505.10655
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Journal reference: Nature Astronomy (2025)
Related DOI:
https://doi.org/10.1038/s41550-025-02537-3
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Submission history
From: Conor Nixon
[v1] Thu, 15 May 2025 18:58:18 UTC (1,776 KB)
https://arxiv.org/abs/2505.10655
Astrobiology,