Titan, one of Saturn’s moons, is the second largest natural satellite in the Solar System, after Ganymede. It is the only moon known to have a dense atmosphere and landscapes reminiscent of Earth’s with hills, lakes and rivers … of hydrocarbons (methane and ethane) and not of water. Such characteristics make certain astronomers not hesitate to consider this star as a planet. A must-see target for NASA’s new space telescope, the James Webb.
Titan’s surface is rarely visible
Titan’s atmosphere is filled with a thick haze that obscures visible light reflected from the surface, making it difficult to see the surface. It was only recently, thanks to a collection of views by the Cassini probe, that astronomers were able to obtain the first detailed maps of its surface. They have also been waiting years to use the infrared vision of James Webb to study Titan’s atmosphere, its fascinating weather patterns and its gaseous composition. The first somewhat blurry images of the telescope were taken by the NIRCam instrument in November 2022. Additional recordings with its second MIRI instrument are expected in May or June 2023. The MIRI data will reveal an even larger part of Titan’s spectrum, including some wavelengths that has never been observed before.
The image (click it for an HD version) on the left uses a filter sensitive to Titan’s lower atmosphere. The bright spots are prominent clouds in the Northern Hemisphere. The image on the right is a color composite image. Several important surface features are marked: Kraken Mare is considered a sea of methane, Belet is dark-colored sand dunes, and Adiri is a bright albedo feature. Credits: NASA, ESA, CSA, A. Pagan (STScI), JWST Titan GTO Team.