astrophsyics

Map of Mimas

The colors shown in these global mosaics are enhanced, or broader, relative to human vision, extending into the ultraviolet and infrared range.

Apart from the moon’s enormous impact crater, named Herschel, a dramatic feature on these maps is the equatorial band on Mimas’ leading hemisphere. Cassini found this band to be significantly brighter in the ultraviolet than surrounding terrains, and it appears somewhat bluish here. This feature, similar to one on Tethys, was found to correlate with the predicted pattern of bombardment of the moons’ surfaces by high-energy electrons trapped in Saturn’s magnetic field. This bombardment is thought to alter the surface ices on a crystalline scale and change their color. Later thermal observations by Cassini’s Composite Infrared Spectrometer (CIRS) instrument showed that these features also form thermal anomalies on the surface, giving rise to the nickname “Pac-Man” features (seePIA16198).

Image Credit: NASA/JPL-Caltech/Space Science Institute/Lunar and Planetary Institute