Life on Saturn

Saturn's small moon Enceladus (seen here to scale) is one of the most exciting places in the Solar System to astronomers who are searching for life beyond our own Earth. The discovery of geysers near the moon's south pole (inset) was totally unexpected and represents one of the many early triumphs of the US/European mission called Cassini/Huygens.

Enceladus is one of the innermost moons of Saturn and it reflects almost 100 per cent of the sunlight that strikes it; as a result, the surface temperature is only -201°C. Since early 2005, the Cassini-Huygens Mission to Saturn has uncovered many mysteries about Enceladus. Here is a timeline of the discoveries:February 2005Cassini's magnetometer discovers an atmosphere around Enceladus, evidence that gases may be escaping from the moon's surface or interior.July 2005Cassini flies within 175km of Enceladus and scientists see unusual geological activity at the moon's south pole.

Instruments show that the south pole is much warmer than expected, suggesting an internal heat source.November 2005Cassini captures the first pictures of a plume of icy material streaming from Enceladus's south pole. Scientists now say this is evidence of geysers like the ones at America's Yellowstone National Park, fed by reservoirs of liquid water.Some experts are now openly speculating about the possibility of finding primitive life forms in the vast ocean that is presumed to exist beneath the frozen surface of Enceladus. Such a prospect would have been considered very remote even a few weeks ago, but during Christmas week, researchers announced the discovery here on Earth of an astonishingly small microbe that thrives in the toxic pink scum of a mine, laden with poisonous metals including arsenic. Four million of them could fit into the full stop at the end of this sentence. The discovery lends further strength to the proposition that life in the Universe is not unique to Earth but is an inherent property of matter.