Astronomers have discovered previously unseen structures and activity in Jupiter’s atmosphere above the Great Red Spot using the James Webb Space Telescope (JWST). These unusual features appear to be caused by powerful atmospheric gravity waves. The Great Red Spot is the largest storm in the solar system, twice as big as Earth, and is believed to have been raging for at least 300 years. The winds of the Great Red Spot rage at around 270 to 425 miles per hour (430 to 680 kilometers per hour), up to 3.5 times as fast as a tornado here on Earth. Despite the storm’s age, size, and power, scientists had suspected that the atmosphere above the Great Red Spot wasn’t particularly interesting. However, these new observations delivered by the JWST’s Near InfraRed Spectrograph (NIRSpec) instrument, which observed the massive scarlet storm in July 2022, show this assumption was wrong.
“We thought this region, perhaps naively, would be really boring,” team leader Henrik Melin of the University of Leicester stated. “It is, in fact, just as interesting as the northern lights, if not more so. Jupiter never ceases to surprise.” Jupiter’s upper atmosphere is the point where the planet’s lower atmosphere meets its magnetosphere. This leads to bright northern and southern lights, powered by bombardment by charged particles from the sun and fueled by sprays of volcanic material erupting from Io, the most active volcanic body in the solar system.
Jupiter is one of the brightest objects in the night sky over Earth, easily seen in clear skies. Yet, apart from its northern and southern lights, the atmosphere of the solar system’s largest planet only glows weakly, making it difficult for ground-based telescopes to see in detail through Earth’s atmosphere. From the JWST’s position a million miles away from Earth, our planet’s atmosphere is no hindrance to this $10 billion space telescope. Additionally, the JWST’s sensitivity in the infrared spectrum allows it to see the gas giant’s atmosphere in intricate detail, including the region over the Great Red Spot. Aiming to discover if this region is somewhat dull, Melin and colleagues targeted it with NIRSpec, the main instrument of the JWST. This led to the discovery of various intricate structures across the JWST’s field of view, including dark arcs and bright spots.
While incident sunlight is responsible for most of the light seen from Jupiter’s atmosphere, the team believes another factor is causing changes in the shape and structure of the upper Jovian atmosphere. “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,” Melin explained. “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.”
These gravity waves are very different from gravitational waves, the latter of which are tiny ripples in space and time predicted by Albert Einstein in his 1915 theory of general relativity. Gravity waves propagate through an atmosphere, as opposed to the fabric of spacetime as gravitational waves do. These atmospheric gravity waves are also seen on Earth occasionally, but these Earthbound waves are much less intense and powerful than the same phenomenon occurring over Jupiter.
The team now hopes to follow up on the detection of these newly found Great Red Spot features and the intricate wave patterns underlying them with the JWST. This future investigation could reveal how the waves flow through the gas giant’s upper atmosphere and how this causes the observed structures to move. The findings are expected to help better understand the distribution of energy across Jupiter and could help support the European Space Agency (ESA) mission JUICE launched on 14 April 2023, which will reach Jupiter and its moons in 2031. JUICE will make detailed observations of Jupiter and its three large ocean moons, Ganymede, Callisto, and Europa. The team’s results are published in the journal Nature Astronomy.
