Webb finds never-before-seen structures above Jupiter’s Great Red Spot

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Using the joint NASA, European Space Agency (ESA), and Canadian Space Agency (CSA) James Webb Space Telescope, a group of scientists has discovered a variety of never-before-seen features in Jupiter’s upper atmosphere. The features were found in the atmospheric region above the iconic Great Red Spot—a high-pressure region in Jupiter’s atmosphere that produces a massive anticyclonic storm that has been visible to astronomers since 1831.

Before the latest observations of the region, scientists believed the region was unremarkable in nature and did not host any intricate atmospheric structures or activity. However, Webb has shown that the region is scientifically interesting, and is already providing scientists with more insight into the inner workings of Jupiter and its enormous atmosphere.

While it may seem easy, observing Jupiter with lots of detail using huge telescopes like Webb and Hubble is difficult. The glow from Jupiter’s upper atmosphere is weak compared to the glow from the planet’s northern and southern polar regions, meaning that visible light telescopes like Hubble and some ground-based telescopes have a harder time observing specific structures within the planet’s upper atmosphere. However, given Webb’s sensitivity to infrared light, the telescope is able to observe the upper atmosphere without interference from the planet’s bright polar regions. Additionally, Webb’s advanced engineering and size means that it can not only collect data on the upper atmosphere but do so with unprecedented detail.

Webb’s observations of the area surrounding the Great Red Spot. (Credit: ESA/Webb/NASA/CSA/Jupiter ERS Team/J. Schmidt/H. Melin/M. Zamani (ESA/Webb))

Jupiter’s upper atmosphere serves as the boundary between the planet’s immense magnetic field and inner atmosphere, and its structure is largely shaped by the interaction between the two regions. For example, the upper atmosphere, with some help from volcanic material ejected by the moon Io, produces bright northern and southern lights. However,  closer to the planet’s equator, the atmospheric structure is largely determined by incoming sunlight, and given that Jupiter only receives four percent of the sunlight that is received on Earth, scientists predicted that this region would be less complex than the more northern and southern regions of the upper atmosphere.

However, this was simply a hypothesis by the scientists, as observations needed to determine the structure of the upper atmosphere in equatorial regions were not yet available — that was until the debut of Webb in 2022.

Webb first observed the equatorial regions of the upper atmosphere, specifically an area located above the Great Red Spot, in July 2022 using the Near-Infrared Spectrograph (NIRSpec) instrument’s Integral Field Unit capabilities. The team of scientists’ main goal with the observations was to investigate the region and determine if the region was dull as had been previously thought by scientists.

When Webb’s observations and data were returned to the team, however, they were surprised to see that the entire region above the Great Red Spot hosts a variety of intricate structures and activity, including dark arcs and bright spots.

“We thought this region, perhaps naively, would be really boring. It is, in fact, just as interesting as the northern lights, if not more so. Jupiter never ceases to surprise,” said lead author Henrik Melin of the University of Leicester in the United Kingdom.

Much of the light emitted from this region is reflected sunlight, however, some of the structures and activity discovered in this area appear to be altered by some mechanism other than sunlight.

“One way in which you can change this structure is by gravity waves – similar to waves crashing on a beach, creating ripples in the sand. These waves are generated deep in the turbulent lower atmosphere, all around the Great Red Spot, and they can travel up in altitude, changing the structure and emissions of the upper atmosphere,” Melin explained.

The atmopshere surrounding the Great Red Spot as imaged by NIRSpec. (Credit: ESA/Webb/NASA/CSA/H. Melin/M. Zamani (ESA/Webb))

Melin et al. explain in their study that these atmospheric waves can sometimes be observed on Earth. However, the waves that occur on Earth are far weaker than those that have been observed on Jupiter by Webb. The team plans to perform follow-up observations of these atmospheric wave patterns to investigate how the waves move through Jupiter’s upper atmosphere. Furthermore, understanding the wave patterns will allow scientists to develop an understanding of how much energy is held in this region and how the structures discovered by Webb change over time.

Webb’s latest observations not only further scientists’ understanding of the Jovian upper atmosphere, but will also help formulate mission planning and future scientific observations on ESA’s Jupiter Icy Moons Explorer, or JUICE, mission. JUICE is currently en route to Jupiter, where it will explore the planet’s three largest ocean-bearing moons, Ganymede, Callisto, and Europa.

Melin et al.’s observations were taken as part of Webb’s Early Release Science (ERS) program 1373. The proposal for the observations was written back in 2017 and was originally written to understand the temperature above the Great Red Spot.

“This ERS proposal was written back in 2017. One of our objectives had been to investigate why the temperature above the Great Red Spot appeared to be high, as at the time recent observations with the NASA Infrared Telescope Facility had revealed. However, our new data showed very different results,” said co-author Imke de Pater of the University of California, Berkeley.

Melin et al.’s results were published in the journal Nature Astronomy.

(Lead image: Jupiter imaged in the near-infrared by Webb’s NIRCam instrument. Credit: NASA/ESA/CSA/Jupiter ERS Team/Ricardo Hueso (UPV/EHU)/Judy Schmidt)

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