Color image of Odysseus Basin on Tethys Target Name:   Tethys Spacecraft:   Voyager 2 Produced by:   Calvin J. Hamilton Copyright:  © 1999 Calvin J. Hamilton Date Released:  28 August 1999 (Publisher Permission Request)

• Saturn's Moon Tethys

Early in the history of Saturn's moon Tethys, an impact occurred forming an enormous 400-kilometer impact basin named Odysseus. The impact scar spans more than two-fifths of the satellite with a diameter slightly larger than Saturn's moon Mimas. When Odysseus was first created, the crater must have been deep with a high mountainous rim and towering central peak. Over time the crater floor relaxed to the spherical shape of the Tethys' surface, and the crater's rim and central peak collapsed. (Similar relaxation is apparent on Jupiter's moons Callisto and Ganymede.) At the time of the Odysseus impact, Tethys must have been sufficiently warm and malleable to allow the topography to collapse. Tethys' interior may have even been liquid. If Tethys had been colder and more brittle at the time of impact, the moon may have been shattered. If it survived the impact, the topography of the crater would have retained its shape similar to Herschel crater on Mimas.

This image was taken by the Voyager 2 spacecraft on August 25, 1981 from a range of 1.1 million kilometers (670,000 miles).