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The “Front” Side of Tethys

Color-composite image of Tethys from Feb. 1, 2017 (NASA/JPL-Caltech/SSI/J. Major)

Color-composite image of Tethys from Feb. 1, 2017 (NASA/JPL-Caltech/SSI/J. Major)

This is a color image of Saturn’s moon Tethys I made from raw images acquired by Cassini on Feb. 1, 2017 in visible-light color channels. It shows the moon’s sunlit leading side—the face that aims in the direction that it moves in its orbit around Saturn. (Click image for a larger version.)

While this icy moon is mostly monochromatic—appearing quite grey even in a color image—there are some subtle variations over large parts of its surface. Here you can just make out a slightly darker bluish band that runs across Tethys’ equatorial region. This is the result of surface weathering by high-energy electrons within Tethys’ orbit. The pale pinker regions to the north and south of the band are thought to be a coating of small ice particles that have been expelled from nearby Enceladus.

Also visible along the terminator is part of the 1,200-mile long, 60-mile-wide Ithaca Chasma, an enormous and ancient canyon system that runs almost all the way from Tethys’ north to south poles.

Tethys is 662 miles (1,065 km) in diameter and composed mostly of water ice and rock. It orbits Saturn at a distance of 183,000 miles (295,000 km) and takes 45.3 hours to complete one orbit. Read more about Tethys here.

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Soar Over the Surface of Tethys with Cassini

Animation of Tethys' surface made from raw Cassini images acquired Nov. 11, 2015. (NASA/JPL-Caltech/SSI. Animation by J. Major.)

Animation of Tethys’ surface made from raw Cassini images acquired Nov. 11, 2015. (NASA/JPL-Caltech/SSI. Animation by J. Major.)

On Nov. 11, 2015, NASA’s Cassini spacecraft passed relatively closely by Saturn’s moon Tethys, one of the ringed planet’s larger icy satellites. The animation above was made from 29 raw images acquired with Cassini’s narrow-angle camera as it passed by; you can see part of the incredibly cratered and ancient surface of this 662 mile (1,065 km) wide moon. Talk about flyover country!

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Dawn Finds Similarities Between Ceres and Saturn’s Moons

Ceres (left, Dawn image) compared to Tethys (right, Cassini image) at comparative scale sizes. (Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA and NASA/JPL-Caltech/SSI. Comparison by J. Major.)

Ceres (left, Dawn image) compared to Tethys (right, Cassini image) at comparative scale sizes. (Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA and NASA/JPL-Caltech/SSI. Comparison by J. Major.)

Around 600 miles wide, covered in craters and cliffs, a composition of rock and water ice… these are descriptions of both several of Saturn’s moons and the dwarf planet Ceres, based on recent observations by NASA’s Dawn spacecraft. New topographical maps show that, in terms of surface features anyway, Ceres shares similarities with Saturn’s icy satellites.

“The craters we find on Ceres, in terms of their depth and diameter, are very similar to what we see on Dione and Tethys, two icy satellites of Saturn that are about the same size and density as Ceres,” said Paul Schenk,  Dawn science team member and a geologist at the Lunar and Planetary Institute (LPI) in Houston, TX. “The features are pretty consistent with an ice-rich crust.”

Read more in my article on Universe Today.

Mighty Melanthius

Raw image from Cassini acquired on April 14, 2012.

The 662-mile-wide Tethys is one of the most heavily cratered worlds in the solar system, tied with sister moons Rhea and Dione. In this recent raw image captured by Cassini on April 14, we can see some of the moon’s larger craters, including Melanthius with its enormous central peak. Read the rest of this entry

A Little Pas de Deux: Tethys and Dione

Saturn's moons Tethys and Dione pass each other from Cassini's point of view. (CLICK TO PLAY)

Saturn’s moon Tethys, its giant Odysseus crater in plain view, passes in front of of the slightly darker Dione in this animation made from several raw images acquired by Cassini earlier this month. Pretty cool!

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