James Webb Space Telescope has revealed an unexpectedly busy patch of Jupiter’s upper atmosphere above the Great Red Spot. In a region scientists once expected to be fairly uniform, Webb found dark arcs, bright spots and long streaks that appear to be shaped by atmospheric waves.
The result comes from observations taken on 27 July 2022 with Webb’s Near-Infrared Spectrograph, or NIRSpec. The team watched the area for 53 minutes and collected six spectral cubes. Each cube covered a 30 by 30 pixel grid, and each pixel represented about 300 kilometers on Jupiter. That gave researchers a rare close look at a region that is hard to study from the ground.
What stood out was not only that the area looked active. It was the fine detail. The paper reports bands and arcs about 1,000 kilometers wide and up to 6,000 kilometers long. Across the field of view, the brightness of the ionized gas changed by as much as a factor of four.
That matters because this is not one of Jupiter’s bright auroral zones near the poles. It is a low-latitude region above the Great Red Spot, the huge storm south of Jupiter’s equator. Scientists had expected sunlight to be the main influence there. Since Jupiter receives only about 4 percent of the sunlight Earth gets, that part of the upper atmosphere was thought to be fairly even from place to place.
Webb showed that it is not.
The telescope could make this measurement because it is very sensitive to infrared light. In Jupiter’s upper atmosphere, a charged form of hydrogen called H3+ glows in the near-infrared. That glow helps scientists trace temperature and ion density high above the cloud tops.
From the ground, that signal is faint. It is also mixed with stronger methane light from lower in the atmosphere. Webb’s NIRSpec instrument can separate those signals much more clearly. In this study, the team used wavelengths from about 2.85 to 4.01 micrometers. They modeled the methane contribution, subtracted it and then measured the H3+ emission lines that remained.
That let them estimate conditions more than 300 kilometers above Jupiter’s cloud deck. The median temperature across the observed region was 713 ± 20 kelvin. The median H3+ column density was 4.5 ± 0.4 × 10^15 per square meter. Those values match earlier broad studies, but the new maps revealed something older observations had missed. The upper atmosphere was not smooth. It was patchy and structured on small scales.
The researchers think gravity waves are the most likely cause.
On Earth, gravity waves form when air is pushed up or down and gravity tries to restore balance. They are not the same as gravitational waves from astrophysics. In an atmosphere, gravity waves can carry energy upward from lower layers. The team suggests that turbulence around the Great Red Spot may generate these waves deep below. As the waves rise, they may change the structure and brightness of the ionosphere above.
That idea helps explain why the region looks so active even though sunlight alone should produce a more even pattern. The paper argues that Jupiter’s low-latitude ionosphere may be more closely linked to the lower atmosphere than scientists had realized.
This adds to a broader picture of Jupiter as a world whose atmospheric layers are strongly connected. The planet’s weather is not only about the cloud tops we can see. Motions lower down can affect the thin gas far above. Webb’s data make that link easier to trace.
The finding also adds a new layer to the story of the Great Red Spot. Astronomers have watched the storm for centuries, yet it still changes in size and shape. Webb’s result suggests its influence may reach much higher than the familiar red oval. Even if the upper atmosphere is not directly part of the storm, it appears to respond to the turmoil below.
There is also a practical reason to follow this work. If researchers can track how these patterns move, they can estimate how energy flows through Jupiter’s upper atmosphere. That remains an open question. Scientists already know Jupiter’s upper atmosphere is hotter than simple sunlight heating would predict. Studies like this may help explain where some of that extra energy comes from.
The team now wants follow-up observations to see how the features change over time. A single observing run can reveal structure. Repeated observations can reveal motion, growth and decay. If the arcs and spots shift in ways expected from gravity waves, that would strengthen the case.
The timing is useful for Jupiter science more broadly. ESA’s Jupiter Icy Moons Explorer, or Juice, is on its way to the Jovian system. Juice will focus on Jupiter and three of its large ocean-bearing moons, but a better picture of Jupiter’s atmosphere and space environment will help that mission as well.
For now, the main result is simple. A place once assumed to be quiet turned out to be full of structure. Webb did more than provide a sharper view of Jupiter. It exposed fine detail in a faint region of the planet that scientists had largely treated as uniform.
The closer researchers look at Jupiter, the more surprises it offers.
References
European Space Agency. (2024, June 25). Astronomers find surprising shapes in Jupiter’s upper atmosphere. ESA/Webb. https://esawebb.org/news/weic2419/
Melin, H., O’Donoghue, J., Moore, L., Stallard, T. S., Fletcher, L. N., Roman, M. T., Harkett, J., King, O. R. T., Thomas, E. M., Wang, R., Tiranti, P. I., Knowles, K. L., de Pater, I., Fouchet, T., Fry, P. H., Wong, M. H., Holler, B. J., Hueso, R., James, M. K., Orton, G. S., Mura, A., Sánchez-Lavega, A., Lellouch, E., de Kleer, K., & Showalter, M. R. (2024). Ionospheric irregularities at Jupiter observed by JWST. Nature Astronomy, 8, 1000-1007. https://doi.org/10.1038/s41550-024-02305-9
National Aeronautics and Space Administration. (n.d.). NIRSpec. NASA Science. https://science.nasa.gov/mission/webb/nirspec/
