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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.

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

Saturn's Moon Tethys

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.

Date November 24, 1995
Credit Credit: NASA, Voyager 2, Copyright Calvin J. Hamilton
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.