European space probe closes for encounter with Titan

On Christmas Day 2004 NASA's Cassini spacecraft, currently in orbit above Saturn, flawlessly released the European Space Agency's 2.7m-wide, 319kg Huygens probe, sending the craft on a 22-day trip towards Titan, the ringed planet's largest moon.

That journey will conclude tomorrow as Huygens, which has spent the last seven years aboard Cassini, attempts to pierce the mysterious moon's atmosphere.

If the probe successfully penetrates Titan's thick, orange-coloured clouds, which have until now prevented scientists observing details of the moon's surface, it will parachute to the surface over a period of two-and-a-half hours, taking photographs and readings along the way.

Scientists are uncertain what kind of surface the probe will encounter when it 'lands', but speculate a richly diverse topography. To splash down in an ocean would probably mean better data from Huygens, as even if the probe lasted only a few minutes before sinking it would at least stay in an upright position, essential for sending the data back to Cassini and to the scientists on Earth. Moreover, some of Huygens's instruments are better prepared to analyse liquids.

If Huygens lands on a solid surface instead, however, there is a higher risk of it falling in the wrong direction and being therefore unable to easily communicate with Cassini.

Anxious scientists anticipate that data from Huygens will contribute to a greater understanding of the moon, as well as of the solar system as a whole.

Titan, the second largest moon in the Solar System (after Ganymede of Jupiter), was discovered by Christiaan Huygens in 1655.

(GB)