Saturn’s rings and Tethys from Cassini (October 29, 2007)

Saturn's rings and Tethys from Cassini (October 29, 2007)

Saturn’s rings and Tethys (October 29, 2007). The gas giant’s dark-side rings glow in shades of brown and gold, contrasting with the more neutral appearance of the icy moon Tethys, which is 1,062 kilometers, or 660 miles across. This view looks toward the anti-Saturn side of Tethys and the unilluminated side of the rings from about 2 degrees above the ringplane. North is up and rotated 35 degrees to the right.

Images taken using red, green and blue spectral filters were combined to create this natural color view. The view was acquired with the Cassini spacecraft narrow-angle camera on October 29, 2007, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees.

Tethys was discovered by the Italian astronomer Giovanni Domenico Cassini (8 June 1625 – 14 September 1712) in 1684, together with Dione, another moon of Saturn, and is named after the titan Tethys of Greek mythology. The Italian astronomer named the four moons he discovered (Tethys, Dione, Rhea and Iapetus) Sidera Lodoicea (“the stars of Louis”) to honor king Louis XIV (5 September 1638 – 1 September 1715), known as Louis the Great (Louis le Grand) or the Sun King (le Roi Soleil), was a monarch of the House of Bourbon who reigned as King of France from 1643 until his death in 1715.

Tethys has a low density of 0.98 g/cm3, the lowest of all the major moons in the Solar System, indicating that it is made of water ice with just a small fraction of rock. This is confirmed by the spectroscopy of its surface. The largest impact crater on Tethys, which can be seen in the image above, Odysseus, is about 250 miles (400 km) in diameter.

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