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Last Updated: Wednesday, 16 November 2005, 13:49 GMT
Moons captured in ring encounter
Cassini captured this encounter between the moons on 22 September (Nasa/JPL/Space Science Institute)

The Cassini spacecraft has captured a striking image of Saturn's moons Dione and Tethys passing each other across the planet's ring system.

The larger moon in the foreground is Dione, which measures 1,126km (700 miles) across, and the smaller moon is the 1,071km- (665-mile-) wide Tethys.

The image was taken in visible light with Cassini's narrow-angle camera on 22 September 2005.

Cassini is at a distance of about 860,000km from Dione in the photo.

The dark groove, or division, that can be seen in the rings shares its name with the orbiting spacecraft.

Italian astronomer Jean Dominique Cassini (1625 -1712) made many observations of Saturn and its moons, discovering the Cassini Division in 1675.

Since entering orbit around Saturn on 1 July 2004, the spacecraft has made two flybys of Dione and five of Tethys.

The pass of Dione revealed a surface covered by craters and fractures exposing bright material to the surface. It is thought to be largely composed of water-ice, with a rocky core.

Cassini's flyby of Tethys showed up a huge crater called Odysseus and a giant fissure called Ithaca Chasma which is roughly 65km (40 miles) wide, and covers three-fourths of Tethys' circumference.

Scientists think the enourmous trench could have been created by the moon's liquid crust hardening before its interior.

The Cassini-Huygens mission is a cooperative project of the US space agency (Nasa), the European Space Agency (Esa) and the Italian Space Agency (Asi).




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