Astronomy Picture of the Day

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

November 24, 1995
See Explanation.  Clicking on the picture will download 
 the highest resolution version available.
Saturn's Moon Tethys
Credit: NASA, Voyager 2, Copyright Calvin J. Hamilton

Explanation: Tethys is one of the larger and closer moons of Saturn. It was visited by both Voyager spacecraft - Voyager 1 in November 1980 and by Voyager 2 in August 1981. Tethys is now known to be composed almost completely of water ice. Tethys shows a large impact crater that nearly circles the planet. That the impact that caused this crater did not disrupt the moon is taken as evidence that Tethys was not completely frozen in its past. Tethys has two moons named Telesto and Calypso that orbit just ahead of it and behind it. Tethys was originally discovered in 1684 by Giovanni Cassini.

Tomorrow's picture: Saturn's Cleanest Moon: Enceladus

| Archive | Glossary | Education | About APOD |
Top 5 logo Best pick logo Cool NASA site logo

Authors & editors: Robert Nemiroff (GMU) & Jerry Bonnell (USRA).
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEA at NASA/ GSFC