Washington  - After delivering spectacular images of Saturn's rings in recent years, NASA's Cassini spacecraft turned its focus Monday to Saturn's moons and how sunlight affects the surfaces of the gas giant and its natural satellites.

Cassini got a new lease on life earlier this year, when NASA approved the programme for another 60 orbits of Saturn and several dozen flybys of the moons Titan, Enceladus, Dione, Rhea and Helene.

During the last four years, Titan has already offered tantilizing evidence of possible habitability and an underground ocean, while Enceladus spouted giant water vapour plumes, thought to come from vaporizing ice.

The findings have answered "all of the objectives we set out to accomplish when we launched. We answered old questions and raised quite a few new ones, and so our journey continues," Bob Mitchell, Cassini programme manager at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement.

The new mission is called Equinox, symbolic of the expectation that Cassini will be around in 2009 during Saturn's vernal equinox, which occurs only at 14-year intervals. Scientists will be able to see what happens as the Sun shifts from south to north of the equator, astronomy. com reported.

The Cassini spacecraft is the first to explore Saturn's system of rings and moons. It entered orbit on June 30, 2004.

Cassini is part of a mission with the ESA's Huygens Probe, which plunged in January 2005 into the atmosphere of another Saturn moon, Titan.

The Cassini-Huygens mission is a cooperative project of NASA, the ESA and the Italian Space Agency. (dpa)