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

TL;DR

This study presents new JWST and Keck observations of Titan's late northern summer, revealing atmospheric composition, chemical processes, and cloud dynamics, thus enhancing understanding of Titan's seasonal climate variations.

Contribution

It provides the first detailed spectroscopic and imaging data of Titan's northern summer atmosphere from JWST and Keck, focusing on chemical species and cloud evolution.

Findings

Detection of methyl radical indicating methane breakdown.

Measurement of CO and CO2 emission bands over a wide altitude range.

Observation of evolving tropospheric clouds and seasonal convection patterns.

Abstract

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.