Cassini takes closer look

2004-10-27 12:11

California - The international Cassini spacecraft began beaming close-up images of Saturn's giant moon Titan to earth late on Tuesday.

Cassini reached the point of closest approach, 1 198 kilometres, at 16:44 GMT and transmitted to Nasa's deep space network antenna in Madrid, Spain, a little under nine hours later.

The first image was a low-resolution scene of a portion of Titan's disk covered in the now familiar hydrocarbon haze. One of the images showed distinct dark and light areas of the surface.

"It takes a bit of processing to bring out features," imaging team leader Carolyn Porco.

There was concern that bad weather in Spain might interfere with some of the night-long data transmissions.

Cassini turned its cameras and instruments toward the cloud-shrouded moon in the closest flyby since it began orbiting Saturn on June 30. Scientists want to see whether Titan has oceans or seas of liquid methane and ethane.

"For those of us who have been studying Titan ... it's very tantalising to say maybe those bright regions are higher icy regions that are popping up out of a dark slushy area, or maybe that's lava that's flowed and covered up some of the terrain and is forming the sharp shoreline-looking boundary," Porco said.

But she said she just didn't know what the images could be.

All together, the spacecraft will make 45 flybys of the moon, coming within 970 kilometres of Titan at times. The spacecraft also carries a probe that will be released on December 24 and plunge into Titan's atmosphere in January, radioing pictures and science data back to Cassini as it descends under a parachute.

Saturn has 33 known moons, including two little ones that were spotted in pictures taken by Cassini in June.

Titan, which is bigger than the planet Mercury, has an atmosphere 1 1/2 times as dense as Earth's and contains organic - meaning carbon-based - compounds.p> Scientists believe those compounds could be much like those on earth billions of years ago before life began. Life, however, is unlikely on Titan because it is so cold.

The $3.3bn spacecraft's first flyby, on July 2, was at a distance of some 320 000 kilometres and proved disappointing. Scientists struggled to discern surface features through what was described as an "organic goo", a hydrocarbon haze likened to smog over Los Angeles.

This time, Cassini was programmed to also use its imaging radar to generate topographical maps and determine whether Titan has a liquid or solid surface.

Cassini was launched in 1997 and flew 3.5 billion kilometres on a roundabout route to Saturn. Nasa said it has worked flawlessly since slipping through a gap in Saturn's shimmering rings to enter orbit.

The mission was funded by Nasa, the European Space Agency and the Italian Space Agency.

On the net:

saturn.jpl.nasa.gov

- AP