Near-infrared observations of Jupiter by NASA’s James Webb Space Telescope (background) revealed previously unsuspected high-elevation winds (red arrows) akin to Earth’s jet stream in a narrow zone above the equator. These winds flow at nearly twice the speed of the winds in the visible cloud layer (blue arrows) 20 miles below, as measured by NASA’s Hubble Space Telescope. Credit: M.H. Wong, UC Berkeley; R. Hueso, University of the Basque Country; NASA; ESA; CSA; STScI; I. de Pater, UC Berkeley; T. Fouchet, Observatory of Paris; L. Fletcher, University of Leicester
NASA’s James Webb Space Telescope has discovered a high-speed jet stream in Jupiter’s atmosphere, moving at 320 miles per hour and situated 15 to 30 miles above the main cloud deck. This jet stream, over 3,000 miles wide, is much faster than the visible cloud layers below, revealing intricate details about Jupiter’s atmospheric dynamics.
Discovery of High-Speed Jet Stream on Jupiter
NASA’s James Webb Space Telescope has discovered a fast-moving jet stream in Jupiter’s atmosphere that is blowing twice as fast as the visible cloud layers below it, creating wind shears that far exceed anything seen on Earth.
The high-speed jet stream, which is traveling at 320 miles per hour (515 kilometers per hour) and is more than 3,000 miles (4,800 kilometers) wide, sits over Jupiter’s equator, 15 to 30 miles (25 to 50 kilometers) above the main cloud deck familiar from optical photos.
This image of Jupiter from NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) shows stunning details of the majestic planet in infrared light. In this image, brightness indicates high altitude. The numerous bright white “spots” and “streaks” are likely very high-altitude cloud tops of condensed convective storms. Auroras, appearing in red in this image, extend to higher altitudes above both the northern and southern poles of the planet. By contrast, dark ribbons north of the equatorial region have little cloud cover. In Webb’s images of Jupiter from July 2022, researchers recently discovered a narrow jet stream traveling 320 miles per hour (515 kilometers per hour) sitting over Jupiter’s equator above the main cloud decks. Credit: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI)
Comparison With Hubble Observations
Based on observations by NASA’s Hubble Space Telescope, winds in the visible cloud layer blow at about 180 mph (250 km/hour). This means that for every kilometer above these visible clouds, the wind speed increases by 7 to 10 kilometers per hour, according to Ricardo Hueso, lead author of a paper describing the findings published recently in the journal Nature Astronomy.
A Surprising Revelation
“This is something that totally surprised us,” said Hueso of the University of the Basque Country in Bilbao, Spain. “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 and move much faster than the typical velocities found in Jupiter’s equator at cloud level.”
Researchers using NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) have discovered a high-speed jet stream sitting over Jupiter’s equator, above the main cloud decks. At a wavelength of 2.12 microns, which observes between altitudes of about 12-21 miles (20-35 kilometers) above Jupiter’s cloud tops, researchers spotted several wind shears, or areas where wind speeds change with height or with distance, which enabled them to track the jet. This image highlights several of the features around Jupiter’s equatorial zone that, between one rotation of the planet (10 hours), are very clearly disturbed by the motion of the jet stream. Credit: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Joseph DePasquale (STScI)
The discovery of this jet stream is giving insights into how the layers of Jupiter’s famously turbulent atmosphere interact with each other, and how the Webb telescope (Webb) is uniquely capable of tracking those features.
Webb’s Advanced Imaging Techniques
The new images of Jupiter were captured in July 2022 by Webb’s NIRCam (Near-Infrared Camera) as part of the Early Release Science (ERS) program. The ERS observations of the Jupiter system are jointly led by Imke de Pater, professor emerita of astronomy at the University of California, Berkeley, and Thierry Fouchet from the Observatory of Paris.
Overall structure of the zonal winds in Jupiter’s atmosphere reconstructed from observations in visible wavelengths (white profile) and different filters used in the study (colored lines). The background image is a color combination of JWST images sensitive to the upper hazes. The right image is a closeup of the central narrow jet above the equatorial region. Credit: NASA/ESA/CSA and Jupiter Early Release Science team
“Even though various ground-based telescopes, spacecraft like NASA’s Juno and Cassini, and NASA’s Hubble Space Telescope have observed the Jovian system’s changing weather patterns, Webb has already provided new findings on Jupiter’s rings, satellites, and its atmosphere,” de Pater said.
The NIRCam obtained images of Jupiter 10 hours apart — one Jupiter day — in four different filters, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere. The wind speed was calculated by tracking the motion of small features, such as clouds — most likely ammonia ice mixed with photochemical haze particles typical of Jupiter’s atmosphere.
“We knew the different wavelengths of Webb 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,” said UC Berkeley co-author Michael Wong, co-investigator for the Jovian system ERS program.
Jupiter has a layered atmosphere, and this illustration displays how Webb is uniquely capable of collecting information from higher layers of the altitude than before. Scientists were able to use Webb to identify wind speeds at different layers of Jupiter’s atmosphere in order to isolate the high-speed jet. The observations of Jupiter were taken 10 hours apart, or one Jupiter day, in three different filters, noted here, each uniquely able to detect changes in small features at different altitudes of Jupiter’s atmosphere. Credit: NASA, ESA, CSA, STScI, Ricardo Hueso (UPV), Imke de Pater (UC Berkeley), Thierry Fouchet (Observatory of Paris), Leigh Fletcher (University of Leicester), Michael H. Wong (UC Berkeley), Andi James (STScI)
Insights Into Stratospheric Phenomena
The high-speed jet stream may be a deep counterpart of a complex phenomenon that has been observed for decades on Jupiter, Saturn, and Earth: regular oscillations of temperatures and winds that occur in the stratosphere, high above these planets’ atmospheres. On Jupiter, these equatorial thermal oscillations between 30 and 150 kilometers above the visible cloud layer have a periodicity of four to six years.
“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,” said team member Leigh Fletcher of the University of Leicester in the United Kingdom. “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.”
Details of the wind speeds (in meters per second) measured by the Webb telescope and the Hubble Space Telescope. Credit: M.H. Wong, UC Berkeley; R. Hueso, University of the Basque Country; NASA; ESA; CSA; STScI; I. de Pater, UC Berkeley; T. Fouchet, Observatory of Paris; L. Fletcher, University of Leicester
Understanding Jupiter’s Zonal Jets
Hueso noted that jets are one of the main features of the atmospheres of both Jupiter and Saturn. They are so perfectly aligned with latitude that they are called zonal jets. These zonal alignments are a consequence of the fast rotation of the planets (both Jupiter and Saturn have a rotation period of about 10 hours), which results in a balance between Coriolis forces and latitudinal gradients of pressure.
In Jupiter and Saturn, the jets are mostly stable in time, with only minor changes at cloud level observed over years and decades.
“To me, the exciting thing is that nobody was expecting this narrow, high-speed jet before JWST,” Wong said. “We knew there was a narrow jet like this on Saturn, so to discover a similar feature on Jupiter enables new comparative studies of the two giant planets, even if the Jupiter jet turns out to have a different formation mechanism.”
Webb’s Enhanced Imaging Capabilities
Astronomers, including de Pater and Wong, have long observed Jupiter in microwave, infrared, visible, and ultraviolet wavelengths using ground and space-based telescopes to study the lower, deeper layers of the planet’s atmosphere, where gigantic storms and ammonia ice clouds reside. Webb’s instruments look farther into the near-infrared than before and are sensitive to the higher-altitude layers of the atmosphere, around 15 to 30 miles (25 to 50 kilometers) above Jupiter’s cloud tops.
So while in earlier near-infrared images these high-altitude hazes have typically looked blurry, with enhanced brightness over the equatorial region, Webb can resolve finer details within the bright hazy bands.
For more on this discovery:
Reference: “An intense narrow equatorial jet in Jupiter’s lower stratosphere observed by JWST” by Ricardo Hueso, Agustín Sánchez-Lavega, Thierry Fouchet, Imke de Pater, Arrate Antuñano, Leigh N. Fletcher, Michael H. Wong, Pablo Rodríguez-Ovalle, Lawrence A. Sromovsky, Patrick M. Fry, Glenn S. Orton, Sandrine Guerlet, Patrick G. J. Irwin, Emmanuel Lellouch, Jake Harkett, Katherine de Kleer, Henrik Melin, Vincent Hue, Amy A. Simon, Statia Luszcz-Cook and Kunio M. Sayanagi, 19 October 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-02099-2
