Nasa scientists will give a spaceprobe a bit of a shower tomorrow when they send it flying through jets of water spouting from a distant world that could be home to alien life.

They will steer their Cassini craft into its closest-ever flyby, skimming just 30 miles past a moon orbiting Saturn called Enceladus.

The scientists are fascinated by geysers erupting from cracks in the rock near the moon’s south pole. They believe the jets may be bursting from a vast underground lake which could be teeming with life.

Cassini will fly into the edges of these plumes while it is still 120 miles from Enceladus and closing in for its unprecedented in-your-face encounter. It is unlikely to get a drenching but will collect samples of water-ice, dust and gas from the flyby.

Experts say the particles in the plumes are the width of a human hair – too small to pose any real threat to the safety of their unmanned probe which has been studying ringed planet Saturn and its family of satellites since 2004.

Nasa associate administrator Alan Stern said: “This daring flyby requires exquisite technical finesse, but it has the potential to revolutionise our knowledge of the geysers of Enceladus. The Cassini mission team is eager to see the scientific results, and so am I.”

The eruptions appear to be happening continuously, showering the 320-mile wide moon’s surface and also adding material to one of Saturn’s spectacular rings. They have already been found to be exerting a significant pull on Saturn itself.

Nasa only discovered that Enceladus is geologically active thanks to the efforts of UK space scientist Professor Michele Dougherty, of Imperial College London.

She pursuaded them to send Cassini just 90 miles above Enceladus in July 2005, a manoeuvre that revealed hot spots from which the dramatic geysers were operating.

The Cassini mission is proving a major success for Nasa, providing a wealth of information and surprises. Only last week, it was discovered that another moon, Rhea, has at least one ring of its own. And Titan has been shown to have rivers and lakes resembling features on Earth beneath its hazy atmosphere.

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