July 18, 2024
1 Solar System Way, Planet Earth, USA

Webb discovers never-before-seen structures on Jupiter's Great Red Spot

Using the James Webb Space Telescope, created jointly by NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA), scientists have discovered a series 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 astronomers have been able to see since 1831.

Before the latest observations of the region, scientists believed it to be unremarkable and not home to any atmospheric structures or intricate activity. However, the Webb telescope has shown that the region is scientifically interesting and is already providing scientists with more information about the inner workings of Jupiter and its enormous atmosphere.

While it may seem easy, observing Jupiter in great detail using huge telescopes like Webb and Hubble is difficult. The glow of Jupiter’s upper atmosphere is faint compared to the glow of the planet’s north and south 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 can observe the upper atmosphere without interference from the planet’s bright polar regions. What’s more, Webb’s advanced engineering and size mean that it can not only collect data about the upper atmosphere, but do so in unprecedented detail.

Webb 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 the inner atmosphere, and its structure is largely determined by the interaction between the two regions. For example, the upper atmosphere, with some help from volcanic material ejected by the moon Io, produces brilliant northern and southern auroras. Closer to the planet's equator, however, atmospheric structure is largely determined by incoming sunlight, and since Jupiter receives only four percent of the sunlight 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 scientists, as the observations needed to determine the structure of the upper atmosphere in equatorial regions were not yet available – that is, until Webb's debut 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 capabilities of the Near Infrared Spectrograph (NIRSpec) instrument's Integral Field Unit. The team of scientists' primary goal with the observations was to investigate the region and determine whether it was opaque, as previously thought.

However, when Webb's observations and data were returned to the team, they were surprised to see that the entire region above the Great Red Spot is home to a variety of intricate structures and activities, including dark arcs and bright spots.

“We thought, perhaps naively, that this region would be really boring. In fact, it is as interesting as the Northern Lights, if not more so. Jupiter never ceases to amaze,” said lead author Henrik Melin of the University of Leicester in the UK.

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

“One way to change this structure is through gravitational waves, similar to waves crashing on a beach and creating ripples in the sand. These waves are generated deep in the turbulent lower atmosphere around the Great Red Spot and can travel to high altitudes, changing the structure and emissions of the upper atmosphere,” Melin explained.

The atmosphere 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 produced on Earth are much weaker than those Webb has observed on Jupiter. The team plans to conduct 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 stored in this region and how the structures discovered by Webb change over time.

Webb’s latest observations not only expand scientific understanding of Jupiter’s upper atmosphere, but will also help inform mission planning and future scientific observations by ESA’s JUpiter Icy Moons Explorer (JUICE) mission. JUICE is currently on its way to Jupiter, where it will explore the planet’s three largest ocean moons: Ganymede, Callisto and Europa.

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

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

The results of Melin et al. were published in the journal Astronomy of nature.

(Main image: Jupiter captured in the near infrared by the NIRCam instrument on the Webb telescope. Credit: NASA/ESA/CSA/Jupiter ERS Team/Ricardo Hueso (UPV/EHU)/Judy Schmidt)

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