Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2007 September 9
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

The Great Basin on Saturn's Tethys
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: Some moons wouldn't survive the collision. Tethys, one of Saturn's larger moons at about 1000 kilometers in diameter, survived the collision, but sports today the expansive impact crater Odysseus. Sometimes called the Great Basin, Odysseus occurs on the leading hemisphere of Tethys and shows its great age by the relative amount of smaller craters that occur inside its towering walls. Another large crater, Melanthius, is visible near the moon's terminator. The density of Tethys is similar to water-ice. The above digitally enhanced image was captured in July by the robot Cassini spacecraft in orbit around Saturn as it swooped past the giant ice ball.

Tomorrow's picture: building galaxies

< | Archive | Index | Search | Calendar | Glossary | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.