Tuesday, November 15, 2005

Dione and Tethys

Every once in a while, as Cassini whizzes around Saturn on its mission of exploration, two or three of the many moons of Saturn will line up in an interesting way (from Cassini’s vantage point). This photo capture two of the major moons in just such a lineup.

Dione is slightly larger than Tethys, and in this picture it’s just over half the distance away from Cassini. The rings, with the Cassini division, are seen nearly edge on.

From the Cassini web site:

The moons Dione and Tethys face each other across the gulf of Saturn’s rings. Here, the Cassini spacecraft looks on the Saturn-facing hemisphere of Tethys below and the anti-Saturn side of Dione above. The dark groove in the rings is the Cassini Division.

Tethys is 1,071 kilometers (665 miles) across, while Dione is 1,126 kilometers (700 miles) across.

This image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 22, 2005, at a distance of approximately 860,000 kilometers (530,000 miles) from Dione. Tethys was on the far side of the rings, 1.5 million kilometers (900,000 miles) from Cassini. The image scale is 5 kilometers (3 miles) per pixel on Dione and 9 kilometers (6 miles) per pixel on Tethys.

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