admin NASA published this original article on June 30, 2023. These new observations are not yet peer-reviewed. Edits by EarthSky.
1st Saturn image from Webb
On June 25, 2023, NASA’s James Webb Space Telescope captured Saturn for its first near-infrared observations of the planet. The initial imagery from Webb’s Near-Infrared Camera (NIRCam) is already fascinating researchers. Saturn itself appears extremely dark at this infrared wavelength. Methane gas absorbs almost all of the sunlight falling on the planet’s atmosphere. However, the icy rings stay relatively bright, leading to the unusual appearance of Saturn’s dark orb.
This image was taken as part of the Webb Guaranteed Time Observation program 1247. The program included several very deep exposures of Saturn. Those images were designed to test the telescope’s capacity to detect faint moons around the planet and its bright rings. Any newly discovered moons could help scientists put together a more complete picture of the current system of Saturn, as well as its past.
Saturn’s rings shine
This new image of Saturn clearly shows details within the planet’s ring system. It also shows several of the planet’s moons: Dione, Enceladus, and Tethys. Additional deeper exposures (not shown here) will allow the team to probe some of the planet’s fainter rings. Scientists hope to get a better look at the thin G ring and the diffuse E ring. Saturn’s rings are made up of an array of rocky and icy fragments. The particles range in size from smaller than a grain of sand to a few as large as mountains on Earth.
Researchers recently used Webb to explore Enceladus, and found a large plume, jetting from the southern pole of the moon, that contains both particles and plentiful amounts of water vapor. This plume feeds Saturn’s E ring.
A closer look at the planet
Saturn’s atmosphere also shows surprising and unexpected detail. Although the Cassini spacecraft observed the atmosphere at greater clarity, this is the first time that we’ve seen the planet’s atmosphere with this clarity at this particular wavelength (3.23 microns). The large, dark, diffuse structures in the northern hemisphere do not follow the planet’s lines of latitude. So this image is lacking the familiar striped appearance we typically see from Saturn’s deeper atmospheric layers. The patchiness is reminiscent of large-scale planetary waves in the stratospheric aerosols high above the main clouds, potentially similar to early Webb observations of Jupiter.
When comparing the northern and southern poles of the planet in this image, the differences in appearance are typical with known seasonal changes on Saturn. For example, Saturn is currently experiencing northern summertime, with the southern hemisphere emerging from the darkness at the end of a winter. However, the northern pole is particularly dark, perhaps due to an unknown seasonal process affecting polar aerosols in particular. A tiny hint of brightening toward the edge of Saturn’s disk might be due to high-altitude methane fluorescence, emission from the trihydrogen ion (H3+) in the ionosphere, or both. Spectroscopy from Webb could help confirm this.
Bottom line: Webb has taken its 1st Saturn image! This infrared view shows Saturn’s rings shining bright in a golden light. You can also spot some of Saturn’s moons.
