James Webb Space Telescope discovers high-altitude jet stream at Jupiter’s equator

• Narrow jet stream discovered near Jupiter’s equator has winds traveling 320 miles per hour.
• It was spotted by the James Webb Space Telescope (JWST).
• University of Leicester’s Leigh Fletcher is co-investigator on the telescope team and analyses the findings.
• Jet stream gives researchers incredible insight into how the layers of the planet’s atmosphere interact with each other.

The James Webb Space Telescope (JWST) has discovered a never-before-seen feature in Jupiter’s atmosphere.

The high-speed jet stream, which spans more than 3,000 miles wide, sits over Jupiter’s equator above the main cloud decks. The discovery of this jet is giving insights into how the layers of Jupiter’s famously turbulent atmosphere interact with each other, and how JWST is uniquely capable of tracking those features.

“This is something that totally surprised us,” said Ricardo Hueso of the University of the Basque Country in Bilbao, Spain, lead author on the paper describing the findings. “What we have always seen as blurred hazes in Jupiter’s atmosphere now appear as crisp features that we can track along with the planet’s fast rotation.”

The research team analysed data from JWST’s NIRCam (Near-Infrared Camera) captured in July 2022. The Early Release Science programme – jointly led by Imke de Pater from the University of California, Berkeley and Thierry Fouchet from the Observatory of Paris – was designed to take images of Jupiter 10 hours apart, or one Jupiter day, in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere.

“Even though various ground-based telescopes, spacecraft like NASA’s Juno and Cassini, and the Hubble Space Telescope have observed the Jovian system’s changing weather patterns, JWST has already provided new findings on Jupiter’s rings, satellites, and its atmosphere,” de Pater noted.

While Jupiter is different from Earth in many ways – Jupiter is a gas giant, Earth is a rocky, temperate world – both planets have layered atmospheres. Infrared, visible, radio and ultraviolet-light wavelengths observed by these other missions detect the lower, deeper layers of the planet’s atmosphere – where gigantic storms and ammonia ice clouds reside.

On the other hand, JWST’s look farther into the near-infrared than before is sensitive to the higher-altitude layers of the atmosphere, around 15-30 miles (25-50 kilometres) above Jupiter’s cloud tops. In near-infrared imaging, high-altitude hazes typically appear blurry, with enhanced brightness over the equatorial region. With JWST, finer details are resolved within the bright, hazy band.

The newly discovered jet stream travels at about 320 miles per hour, twice the sustained winds of a Category 5 hurricane here on Earth. It is located around 25 miles above the clouds, in Jupiter’s lower stratosphere.

By comparing the winds observed by JWST at high altitudes, to the winds observed at deeper layers from Hubble, the team could measure how fast the winds change with altitude and generate wind shears.

While JWST’s exquisite resolution and wavelength coverage allowed for the detection of small cloud features used to track the jet, the complementary observations from Hubble taken one day after the JWST observations were also crucial to determine the base state of Jupiter’s equatorial atmosphere and observe the development of convective storms in Jupiter’s equator not connected to the jet. 

“We knew the different wavelengths of JWST and Hubble would reveal the three-dimensional structure of storm clouds, but we were also able to use the timing of the data to see how rapidly storms develop,” added team member Michael Wong of the University of California, Berkeley, who led the associated Hubble observations.

The researchers are looking forward to additional observations of Jupiter with JWST to determine if the jet’s speed and altitude change over time.

“Jupiter has a complicated but repeatable pattern of winds and temperatures in its equatorial stratosphere, high above the winds in the clouds and hazes measured at these wavelengths,” explained team member Leigh Fletcher, from the University of Leicester School of Physics and Astronomy. “If the strength of this new jet is connected to this oscillating stratospheric pattern, we might expect the jet to vary considerably over the next two-to-four years – it’ll be really exciting to test this theory in the years to come.”

“It’s amazing to me that, after years of tracking Jupiter’s clouds and winds from numerous observatories, we still have more to learn about Jupiter, and features like this jet can remain hidden from view until these new NIRCam images were taken in 2022,” continued Fletcher, who is co-investigator on the team and helps to analyse the findings.

He added: “These new discoveries in Jupiter’s atmosphere are part of a wider programme of exploration of the giant planets with JWST led by scientists here at the University of Leicester. These include our recent investigation of Saturn’s seasonal atmosphere, and forthcoming new observations of Uranus and Neptune – there’s lots more still to come.”

Fletcher is also one of the interdisciplinary scientists on the European Space Agency’s (ESA) Jupiter Icy Moons Explorer (JUICE) team, which will observe the giant gas planet Jupiter and its three large ocean-bearing moons: Ganymede, Callisto and Europa. These moons are crucial to understand if life could ever have existed beyond Earth.

He said: “These new findings help us to prepare for the scientific operations for JUICE in the years to come – Leicester is a co-investigator on several remote sensing instruments that will explore the inner workings of Jupiter’s enormous atmosphere in the 2030s.”

The researchers’ results were recently published in Nature Astronomy.

The James Webb Space Telescope is the world’s premier space science observatory. JWST is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. JWST is an international program led by NASA with its partners, ESA and the Canadian Space Agency.