Mars might dominates the search for extraterrestrial life in our solar system, but a growing number of scientists believe Enceladus, an icy moon of Saturn, is a much better bet. Many now believe it offers the best hope we have of discovering life on another world inside our solar system.
As a a moon, Enceladus with its mere 310 miles in diameter is quite small, and is orbiting in deep, cold space, 1 billion miles away from the warmth of the sun. However, what makes Enceladus a prime candidate for harboring life -- it got liquid water, organic material and a source of heat. Cassini's observations suggest Enceladus possesses a subterranean ocean that is kept liquid by the moon's internal heat. The unknown source of energy is producing around 16 gigawatts of power and looks very like the geothermal energy sources we have on Earth – like the deep vents we see in our ocean beds and which bubble up hot gases.
At the moon's south pole, Enceladus's underground ocean appears to rise close to the surface. At a few sites, cracks have developed and water is bubbling to the surface before being vented into space, along with complex organic chemicals that also appear to have built up in its sea.
Equally remarkable is the impact of this water on Saturn. The planet is famed for its complex system of rings, made of bands of small particles in orbit round the planet. There are seven main rings: A, B, C, D, E, F and G, and the giant E-ring is linked directly with Enceladus. The water the moon vents into space turns into ice crystals and these feed the planet's E-ring. If all geysers of Enceladus were turned off, the great E-ring of Saturn would disappear within a few years. For a little moon, Enceladus has quite an impact.