The James Webb Space Telescope (JWST) has accomplished some spectacular feats since it began operations in 2021. Thanks to its sensitivity in the near- and mid-infrared wavelengths, it can take detailed images of cooler objects and reveal things that would otherwise go unnoticed. This includes the iconic image Webb took of Jupiter in August 2022, which showed the planet’s atmospheric features (including its polar aurorae and Great Red Spot) in a new light. Using Webb, a team of European astronomers recently observed the region above the Great Red Spot and discovered previously unseen features.
The team was led by Dr. Henrik Melin, an STFC JWST Fellow and Planetary Scientist from the University of Leicester. He was joined by researchers from the University of Reading, the Space Telescope Science Institute (STScI), the JAXA Institute of Space and Astronautical Science, the Center for Space Physics at Boston University, the Observatoire de Paris, the SETI Institute, NASA’s Jet Propulsion Laboratory, and multiple universities. The paper that describes their observations recently appeared in the journal Nature Astronomy.
The team conducted integral field spectroscopy (IFS) of Jupiter’s Great Red Spot using Webb’s Near-InfraRed Spectrograph (NIRSpec) in July 2022. This process involves dissecting an astronomical image into multiple spatial components and dispersing them with a spectrograph to provide spatially resolved information. Their observations were made as part of an Early Release Science program titled “ERS Observations of the Jovian System as a Demonstration of JWST’s Capabilities for Solar System Science.”
Interestingly, the discovery was completely unexpected, as the team attempted to study Jupiter’s upper atmosphere in more detail. Compared to Jupiter’s bright aurorae, the glow from the planet’s ionosphere is weak, making it difficult for ground-based telescopes to conduct detailed observations of this region. Scientists have been especially interested in studying Jupiter’s ionosphere since it is where Jupiter’s atmosphere and magnetic field begin to interact. It is within this layer that Jupiter’s polar aurorae can be seen, which are fueled by material ejected by Io’s many active volcanoes.
Closer to the equator, the structure of the planet’s upper atmosphere is influenced by incoming sunlight. Because Jupiter receives only 4% as much sunlight as Earth, astronomers expected this region of the atmosphere to be homogenous. However, the team was surprised that this region contained intricate wave patterns, including dark arcs, bright spots, and other structures. As Dr. Melin explained in an ESA press release:
“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. 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.”
Since sunlight drives the light emitted from the planet’s ionosphere, the team suspects that another mechanism is responsible for altering the shape and structure of this region. In the future, the team hopes to conduct follow-up observations of these wave patterns to investigate how they move within Jupiter’s upper atmosphere and how they change over time. These findings could also inform the ESA’s Jupiter Icy Moons Explorer (JUICE), which will reach Jupiter and begin conducting detailed observations in 2031.
Further Reading: ESA