Home Science Space Webb Telescope Will Study Jupiter, Its Rings, and 2 Intriguing Moons

Webb Telescope Will Study Jupiter, Its Rings, and 2 Intriguing Moons

Jupiter, named for the king of the ancient Roman gods, commands its own mini-version of our solar system of circling satellites; their movements convinced Galileo Galilei that Earth is not the center of the universe in the early 17th century. More than 400 years later, astronomers will use NASA’s James Webb Space Telescope to observe these famous subjects, pushing the observatory’s instruments to their fullest capabilities and laying the groundwork for far-reaching scientific discovery.

The moon Io orbits Jupiter in this image from NASA's Cassini spacecraft. Jupiter and Io appear deceptively close in this image, when in fact the moon is orbiting 217,000 miles from the gas giant planet. (Image: NASA/JPL/University of Arizona)
The moon Io orbits Jupiter in this image from NASA’s Cassini spacecraft. Jupiter and Io appear deceptively close in this image, when in fact the moon is orbiting 217,000 miles from the gas giant planet. (Image: NASA / JPL / University of Arizona)

A diverse team of more than 40 researchers, led by astronomers Imke de Pater of the University of California, Berkeley and Thierry Fouchet of the Observatoire de Paris, have designed an ambitious observing program that will conduct some of Webb’s first scientific observations in the solar system — studying Jupiter, its ring system, and two of its moons — Ganymede and Io. De Pater said:


In addition to calibrating Webb’s instruments for Jupiter’s brightness, astronomers must also take into account the planet’s rotation, because Jupiter completes one day in only 10 hours. Several images must be stitched together in a mosaic to fully capture a certain area — the famous storm known as the Great Red Spot, for example — a task made more difficult when the object itself is moving. While many telescopes have studied Jupiter and its storms, Webb’s large mirror and powerful instruments will provide new insights. De Pater said:

Cyclone storms encircle Jupiter's North Pole, captured in infrared light by NASA's Juno spacecraft. (Image: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM)
Cyclone storms encircle Jupiter’s North Pole, captured in infrared light by NASA’s Juno spacecraft.
(Image: NASA / JPL-Caltech / SwRI / ASI / INAF / JIRAM)

Webb will also examine the atmosphere of the polar region, where NASA’s Juno spacecraft discovered clusters of cyclones. Webb’s spectroscopic data will provide much more detail than has been possible in past observations, measuring winds, cloud particles, gas composition, and temperature. Future solar system observations of the giant planets with Webb will benefit from the lessons learned in these early observations of the Jovian system. The team is tasked with developing methods for working with Webb observations of solar system planets, which can be used later by other scientists.


All four of the gas giant planets of the solar system have rings, with Saturn’s being the most prominent. Jupiter’s ring system is composed of three parts: a flat main ring; a halo inside the main ring, shaped like a double-convex lens; and the gossamer ring, exterior to the main ring. Jupiter’s ring system is exceptionally faint because the particles that make up the rings are so small and sparse that they do not reflect much light. Next to the brightness of the planet, they practically disappear, presenting a challenge for astronomers. Co-investigator Michael Wong of the University of California, Berkeley said:

NASA's Galileo spacecraft captured an image of Jupiter's ring system, including the diffuse outer gossamer ring. (Image: NASA/JPL/Cornell University)
NASA’s Galileo spacecraft captured an image of Jupiter’s ring system, including the diffuse outer gossamer ring. (Image: NASA / JPL / Cornell University)

The team will test observing strategies to deal with Jupiter’s scattered light and build models for use by other astronomers, including those studying exoplanets orbiting bright stars. The team will look to make new discoveries in the rings as well. De Pater noted that there may be undiscovered “ephemeral moonlets” in the dynamic ring system, and potential ripples in the ring from comet impacts, like those observed and traced back to the impact of Comet Shoemaker-Levy 9 in 1994.


Several features of icy Ganymede make it fascinating for astronomers. Aside from being the largest moon in the solar system, larger even than the planet Mercury, it is the only moon known to have its own magnetic field. The team will investigate the very outer parts of Ganymede’s atmosphere, its exosphere, to better understand the moon’s interaction with particles in Jupiter’s magnetic field.

There is also evidence that Ganymede may have a liquid saltwater ocean beneath its thick surface ice, which Webb will investigate with a detailed spectroscopic study of surface salts and other compounds. The team’s experience studying Ganymede’s surface may be useful in the future study of other icy solar system moons suspected of having subsurface oceans, including Saturn’s moon Enceladus and fellow Jovian satellite Europa.


In dramatic contrast to Ganymede is the other moon the team will study, Io, the most volcanically active world in the solar system. The dynamic surface is covered with hundreds of huge volcanoes that would dwarf those on Earth, as well as lakes of molten lava and smooth floodplains of solidified lava. Astronomers plan to use Webb to learn more about the effects of Io’s volcanos on its atmosphere. De Pater said:

Another mystery Webb will investigate on Io is the existence of “stealth volcanoes,” which emit plumes of gas without the light-reflecting dust that can be detected by spacecraft like NASA’s Voyager and Galileo missions, and so have thus far gone undetected. Webb’s high spatial resolution will be able to isolate individual volcanoes that previously would have appeared as one large hotspot, allowing astronomers to gather detailed data on Io’s geology.

NASA's Galileo spacecraft catches Io in the midst of a volcanic eruption. (Image: NASA/JPL/DLR)
NASA’s Galileo spacecraft catches Io in the midst of a volcanic eruption.
(Image: NASA / JPL/DLR)

Webb will also provide unprecedented data on the temperature of Io’s hotspots and determine if they are closer to volcanism on Earth today, or if they have a much higher temperature, similar to the environment on Earth in the early years after its formation. Previous observations by the Galileo mission and ground observatories have hinted at these high temperatures; Webb will follow up on that research and provide new evidence that may settle the question.

Team Effort

Webb’s detailed observations will not supplant those of other observatories, but rather coordinate with them, Wong explained, saying:

In turn, Webb’s study of Jupiter’s storms and atmosphere will complement Juno data, including radio signals from lightning, which Webb does not detect. Wong concluded, saying:

Provided by: Leah Ramsay/Christine Pulliam, NASA’s Goddard Space Flight Center [Note: Materials may be edited for content and length.]

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  • Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

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