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Last Updated: Friday, 5 November, 2004, 14:55 GMT
Titan moon holds on to enigma
The pictures are the closest ever taken of the moon

Scientists are none the wiser as to what awaits the Huygens space probe on Saturn's moon Titan when it lands, despite a close pass by its mothership.

The Cassini spacecraft will release the piggybacked Huygens probe towards Titan's atmosphere on Christmas Day.

It is thought Huygens could land on an ocean of liquid hydrocarbon, on solid ice, or squelch down on sludge.

UK mission scientists say that none of the landing scenarios that researchers envisaged have yet been ruled out.

On 26 October, Cassini slipped closer to Saturn's largest moon than it has ever been before and took highly detailed images of the surface with its cameras.

Image clarity

Mark Leese, of the Open University, programme manager for Huygens' surface science package [SSP], said: "It's interesting that all of the possible landing scenarios that we envisaged - a hard crunch on to ice, a softer squelch into solid organics or a splash-down on a liquid hydrocarbon lake - still seem to exist on Titan."

"Black cat" on Titan

Scientists hoped Cassini's instruments would penetrate the thick chemical haze which shrouds Titan that has foiled previous attempts to see through to the surface.

Though Cassini certainly succeeded in this, the enigmatic pictures have still left mission scientists at a loss to interpret some of the features they can see.

Professor Carl Murray, from Queen Mary, University of London, said the pictures of Titan revealed the surface has a diverse set of features.

"We see bright and dark areas roughly aligned in an east-west direction. These are similar to wind streaks seen on Mars and may indicate that material on Titan has been deposited by the effects of wind blowing across the landscape."

Valuable data

But scientists are hopeful that detailed analysis of the data, which is currently underway, should help them solve some of the moon's enigmas.

1. Antennas enabling communication with Earth
2. Boom carrying instrument to measure magnetic fields
3. Two cameras will take 300,000 pictures of the planet
4. Infra-red spectrometer analyses Saturn's temperature and composition
5. Radioisotope thermoelectric generators supply 750W of power
6. Cassini has two engines - one is a back-up
7. Thrusters used for small changes of direction or speed
8. Huygens probe will land on Saturn's largest moon, Titan
9. Plasma spectrometer measures charged particles and solar winds
Professor John Zarnecki, of the Open University, and lead scientist for Huygens' surface science package, said: "Titan is geologically active but hasn't yet given up all of its secrets.

"Combining the visible images with infrared and [data from the radar instrument] from this and future fly-bys should help to clarify the picture."

Scientists working on data from Cassini's electron spectrometer instrument think it will be possible to use results from the data this instrument gathered on the fly-by to understand what Titan's upper atmosphere is made of.

"Our electron results contain tell-tale fingerprints of photoelectrons and Auger electrons which we will use for this," said Dr Andrew Coates, of the Mullard Space Science Laboratory in London.

"Also, the total picture shows how important electrons - raining down on Titan's upper atmosphere - are in helping the feeble sunlight drive the complex chemistry in [the moon's] upper atmosphere."

Professor Michele Dougherty, from Imperial College in London, and lead scientist on Cassini's Magnetometer, said early results from the fly-by suggested Titan did not have a magnetic field.

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