Vortex at the North Pole of Uranus

Thanks to observations from the Very Large Array, we have discovered a persistent vortex at the North Pole of the planet Uranus
Three views of Uranus showing its newly discovered bright polar cap. In these images, it appears white, green, and blue, processed from microwave light. Credit:

For the first time, a vortex has been detected beneath the clouds of Uranus, providing strong evidence of the existence of a cyclone anchored to the planet’s North Pole. Recent findings tell us that Uranus is not as atmospherically inert as it initially seemed. Long gone are the considerations made when NASA‘s Voyager 2 spacecraft flew over the “ice giant” in January 1986.

The discovery of a northern vortex on Uranus was made through the detection of thermal emission in the form of radio waves captured using the Very Large Array (VLA) of radio telescopes in New Mexico.

Polar vortices in the Solar System

Polar vortices appear to be a common feature of all planets with atmospheres, at least in our Solar System. They have previously been observed on Venus, Earth, Mars, Jupiter, Saturn, Uranus (at its South Pole), and Neptune. It is believed that high-altitude atmospheric jet streams are responsible for the formation of these vortices, although the details differ on each planet.

When Voyager 2 flew over Uranus, it detected wind speeds of approximately 900 km/h at the planet’s South Pole. However, the probe did not have a view of the planet’s North Pole. Adding to this lack of data was the inability to observe it from Earth until recently. This is because Uranus orbits the Sun tilted on its side at an angle of 97.8° relative to the orbital plane. In other words, for a long time, we could only see the equatorial region of the planet from our perspective.

However, since 2015, Uranus has rotated enough to allow us to begin to have a clearer view of its North Pole. In 2018 and 2022, the Hubble Space Telescope observed a bright cap above Uranus’ North Pole, the first evidence of a polar cyclone.

VLA observations

Now, VLA observations of Uranus in 2015, 2021, and 2022 have measured atmospheric circulation and temperature changes in this polar cap. The VLA detected a “dark collar” surrounding the planet at 80° latitude. Within this belt, a bright spot was detected, indicating a temperature several degrees warmer at the center of the vortex. A central spot with these characteristics is typical of a cyclone.

“These observations tell us much more about the history of Uranus” said (rif.Alex Atkins of NASA’s Jet Propulsion Laboratory (JPL), who led the observations in a statement. “It is a much more dynamic world than one might think”. Unlike terrestrial cyclones, Uranus’ polar vortex is not composed of water vapor but rather methane, ammonia, and hydrogen sulfide. Furthermore, the storm remains firmly anchored to the pole. Little else is currently known.

In the recent Planetary Science and Astrobiology Decadal Survey published by the US National Academies, Uranus is a priority for a new space mission. To support this objective, planetary scientists are doubling their efforts to study Uranus to help inform the scientific goals of any future mission.

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