Overview

• Findings published in Geophysical Research Letters and presented at the EPSC-DPS2025 meeting detail previously unseen structures in Saturn’s upper atmosphere.
• During a continuous 10-hour NIRSpec observation on November 29, 2024, JWST mapped H3+ in the ionosphere around 1,100 km altitude and methane in the stratosphere near 600 km.
• The ionosphere showed dark, bead-like features embedded in bright auroral halos that held their shape for hours and drifted slowly over longer periods.
• An asymmetric four-armed, star-like pattern appeared in the stratosphere over the same geographic region, with an apparent alignment to the darkest beads that remains unconfirmed.
• The team proposes magnetosphere–atmosphere coupling and possible links to the deeper hexagonal jet as hypotheses, noting that these layers cannot be probed from the ground and require rapid JWST monitoring during equinox.