Cassini Data: 101 Geysers on Saturn's Moon Enceladus Rise from Sea below Icy Shell

Scientists have identified the 101 distinct geysers erupting on Saturn's icy moon Enceladus as having their origins in the sea beneath the icy shell.

The scientists suggest it is possible for liquid water to reach from the moon's underground sea all the way to its surface.

There has been much speculation that the ocean of liquid water beneath its icy crust may be capable of supporting life as we know it. The water ocean on Enceladus is about 6 miles (10 kilometres) deep and lies beneath a shell of ice 19 to 25 miles (30 to 40 km) thick, researchers say.

Further, it's in direct contact with a rocky seafloor, theoretically making possible all kinds of complex chemical reactions that led to life on Earth.

The present study looked at mission data recovered from the Cassini spacecraft over seven years. The analysis has been published in two articles in the current online edition of the Astronomical Journal.

Situated in the south polar terrain with its four tiger-stripe fractures, the geysers of tiny icy particles were first sighted 10 years ago.

The present analysis concludes that the geysers do not originate due to heat but are in turn the cause of the small hot spots detected by Cassini.

The geysers have much deeper roots and the only plausible source of the material is the sea known to exist beneath the ice shell.

After the first sighting of the geysers in 2005, scientists had suspected the geysers to be a product of friction generated by rubbing of the walls of the fractures.

Alternate views held that the opening and closing of the fractures during the moon's orbital movement allowed water vapour from below to reach the surface.

When they compared the geysers' locations with low-resolution maps of thermal emission, it became apparent the greatest geyser activity coincided with the greatest thermal radiation. Comparisons between the geysers and tidal stresses revealed similar connections. But the question remained, "What produces what?"

The answer to this mystery came from comparison of the survey results with high-resolution data collected in 2010 by Cassini's heat-sensing instruments.

In the companion paper, the authors look at the periodic variation in the brightness of the plume formed by all the geysers as Enceladus orbits Saturn.

They found the simplest model of tidal flexing provides a good match for the brightness variations Cassini observes, but it does not predict the time when the plume begins to brighten. Some other important effect is at work.

The Cassini-Huygens mission is a cooperative project of Nasa, the European Space Agency and the Italian Space Agency.