Cassini primed for extended tour of Saturn
BY DR EMILY BALDWIN
ASTRONOMY NOW
Posted: June 2, 2008

On May 28, the Cassini spacecraft successfully completed a flyby of Saturn’s moon Titan, the last flyby of the original four-year tour, but Cassini’s exploration of Saturn will now continue with a two-year extended mission.

The most recent flybys present imagery of Titan’s mountainous region Xanadu, which revealed a set of three parallel ridges spaced about 50 kilometres apart, interpreted as tilted blocks of broken up crust. Their regular spacing is typical of regions that have been compressed or extended over large areas, just like the western United States Basin and Range Province. These features are common to Titan’s equatorial region and will help scientists to better understand the processes that operate in Titan's crust and interior, and how they differ to Earth’s unique plate tectonics driven motion of the crust.

A set of three parallel ridges seen during the May 12 radar flyby. The resolution is about 300 metres. The bright areas show that material here is fractured or blocky, and the radar-dark features are interpreted as cliffs or faults with heights up to a few hundred metres. Image: NASA/JPL.

A new impact crater was also discovered in the recent flyby imagery, just the fourth crater on Titan definitely identified as one, out of a possible 100 features that are regarded as potential impact craters. Compared with other Saturnian moons which show evidence for thousands of impact events, Titan has a dense and highly impenetrable atmosphere which burns up smaller impacting bodies before they can hit the surface. Because Titan is such a dynamic world, active processes such as wind-driven sand and icy volcanism may fill any existing depressions, further conspiring to erase its impact history.

A newly discovered impact feature on Titan, approximately 112 kilometres in diameter. It is located some 100 kilometres north of the Huygens landing site. Image: NASA/JPL.

The May flybys of Titan conclude Cassini’s “Prime” four-year odyssey and the spacecraft will now spend the next three months in a highly inclined orbit, viewing Saturn from a unique angle such that its spectacular ring system will appear spread out like a giant halo. The extended mission, named the “Saturn Equinox Mission”, will begin in July, a two-year finale with 26 Titan flybys, 7 Enceladus encounters, and one flyby each of icy moons Dione, Rhea and Helene.