On June 25, 2023, the James Webb Space Telescope of NASA directed its first near-infrared observations to the world-renowned Saturn. The initial imagery from Webb’s NIRCam (Near-Infrared Camera) has already amazed the researchers. In the infrared wavelength observed by the telescope, Saturn appears to be extremely dark as the methane gas absorbs almost all of the sunlight that falls on its atmosphere. On the other hand, the icy rings of Saturn stay relatively bright and this leads to its unique appearance in the Webb image. The data gathered from this observation will be further processed to comprehend its physical characteristics and understand more about its rings and atmosphere. In addition to this, it will also provide a better insight into the planet’s climate and form an understanding of its evolution throughout time.
Image of Saturn was taken as part of Webb Guaranteed Time Observation program 1247, which included several deep exposures of the planet. The goal of the program was to detect any faint moons around Saturn and better understand its current and past system. The image shows details within the planet’s ring system, along with three of its moons: Dione, Enceladus, and Tethys. Additional deeper exposures will allow researchers to probe some of the planet’s fainter rings, including the thin G ring and the diffuse E ring. These rings are made up of an array of rocky and icy fragments, ranging in size from smaller than a grain of sand to a few as large as mountains on Earth. Using this data, Webb recently explored Enceladus and found a large plume jetting from its southern pole containing particles and water vapor.
Saturn’s atmosphere has been seen with surprising and unexpected detail, with the Cassini spacecraft offering the greatest amount of clarity. This particular image, taken at 3.23 microns, is unique to Webb and does not show the familiar striped appearance typically seen from Saturn’s deeper atmospheric layers. Instead, large dark diffuse structures can be seen in the northern hemisphere that do not follow the planet’s lines of latitude. This patchiness is reminiscent of large-scale planetary waves in the stratospheric aerosols high above the main clouds, which is similar to those seen in early Webb NIRCam observations of Jupiter.
The northern and southern poles of the planet in this image clearly demonstrate the typical seasonal changes Saturn is known for. Currently, the planet is experiencing northern summertime, while the southern hemisphere is emerging from its winter darkness. The northern pole is notably darker than usual, which could be caused by an unknown seasonal process affecting the polar aerosols. A slight hint of brightness around the edge of the disk may be due to high-altitude methane fluorescence, H3+ emission from the ionosphere, or both; spectroscopy from the James Webb Space Telescope could help confirm this.
The countless missions conducted by NASA such as Pioneer 11, Voyagers 1 and 2, Cassini, and Hubble have been tracking Saturn’s atmosphere and rings for decades. These observations from Webb will further provide interesting insights into Saturn’s story in the years to come as the science team thoroughly analyzes the data to prepare it for peer-reviews. This enables to understand more about the planet’s atmosphere, composition, and its many moons, including Enceladus and Titan. What’s more, the images taken from Webb will be of much higher quality than ever before, allowing us to observe Saturn in more detail than ever before.