Clouds lift to reveal Titan's wet secret

THE Solar System is turning out to be a wetter place than we thought. Rather than the desolate, dry habitat that had been depicted, new data has shown that yet another planet's moon - this time Saturn's largest, Titan - has water vapour in its atmosphere.

Coming after last month's revelation that there is water frozen at our own Moon's poles, it shows that the essential compound for life is surprisingly plentiful.

The discovery of the distinctive spectrometry "signature" of water molecules on Titan by the European Infrared Space Observatory (ISO) means that the satellite is remarkably like the early Earth. Though the water is probably not in the form of oceans, it is at least a component of the moon's atmosphere.

Previously, Titan had been shrouded in mystery, covered in a thick atmosphere of orange clouds containing organic chemicals like those from which primordial life developed here 4 billion years ago. Last year the European Space Agency and the US space agency Nasa launched the Cassini mission, containing the ESA Huygens probe which will crash-land on Titan in 2004.

Athena Coustenis, of the Paris Observatory in France who was one of the chief astronomers in the ISO team, said: "Water vapour makes Titan much richer. We knew there was carbon monoxide and carbon dioxide in Titan's atmosphere, so we expected water vapour too. Now that we believe we have found it, we can expect to better understand the organic chemistry taking place on Titan and also the sources of oxygen in the Saturnian system."

A team from Imperial College, London, has used the ISO to find galaxies so far away that when the light left them the universe was only one-third of its present age of about 15 billion years. Infrared images of the Horsehead Nebula, a large dust cloud 1,500 light years away in the constellation of Orion, have illuminated newly formed stars embedded in the horse's "head".