For the first time, scientists have mapped the upper atmosphere of Uranus in three dimensions — and the findings are pulling back the curtain on one of the solar system’s most puzzling worlds.

The research, led by PhD student Paola Tiranti at Northumbria University in the UK, was published this week in Geophysical Research Letters. Using the James Webb Space Telescope’s Near-Infrared Spectrograph during a 15-hour observation session on January 19, 2025, Tiranti and an international team were able to chart the vertical structure of Uranus’ ionosphere with unprecedented detail.

A Tilted, Turbulent Planet

Uranus is the odd one out in our solar system. Its rotation axis is tilted nearly 98 degrees — it rolls on its side relative to its orbit — and its magnetic field is offset a further 60 degrees from that axis. The result is a planetary environment so geometrically complex that its atmosphere has long defied detailed study.

The new Webb data changes that. For the first time, researchers can track how energy moves upward through distinct layers of the atmosphere, and observe directly how the planet’s skewed magnetic field sculpts the auroras glowing thousands of kilometres above the cloud tops.

What the Map Reveals

The three-dimensional atmospheric portrait shows that temperatures in the upper atmosphere peak between 3,000 and 4,000 kilometres above the cloud tops, while concentrations of charged particles — ion densities — reach their maximum at roughly 1,000 kilometres altitude.

Two bright auroral bands were detected near the magnetic poles, separated by a distinct depletion zone. The pattern reflects the intricate dance between Uranus’ offset magnetic field and the solar wind’s charged particles.

The data also confirms a troubling long-term trend: Uranus’ upper atmosphere has been cooling steadily for at least 30 years, dropping an average of 426 kelvins — around 150°C — over that period. What is driving this prolonged cooling remains an open question.

A Blueprint for Distant Worlds

The findings matter beyond our own solar neighbourhood. Ice giants like Uranus are now understood to be one of the most common planet types in the galaxy. Understanding how energy flows through their atmospheres gives scientists a working model for interpreting the signals from thousands of exoplanets orbiting distant stars.

NASA’s planetary science decadal survey has ranked a dedicated Uranus mission as its top priority for the coming decade. Research like Tiranti’s is laying the groundwork for what that mission will need to look for when it eventually arrives.

Source: Geophysical Research Letters — “JWST Discovers the Vertical Structure of Uranus’ Ionosphere” (DOI: 10.1029/2025GL119304)