Icy moon blasts liquid water
Scientists say the Saturnian moon has geysers shooting plumes of water at speeds of more than 2000 kilometres per hour (Source: Karl Kofoed/NASA)
Huge plumes of water vapour and ice particles are spewing from Saturn's moon Enceladus at supersonic speeds in a way that strongly suggests they come from liquid water down below the icy surface, say scientists.
The research, published in the journal Nature, offers new evidence that the moon may harbor an underground ocean of water, meaning conditions might exist that could support life, even if only microbial organisms.
"We think liquid water is necessary for life," says Dr Candice Hansen of NASA's Jet Propulsion Laboratory in California.
"This is more evidence that there is liquid water there. You also need energy, you need nutrients, you need organics. It looks like the pieces are there. Whether or not there's actually life, of course, we can't say," she says.
In 2005, the Cassini spacecraft discovered humongous geysers erupting from fissures near the south pole of Enceladus.
Since then, scientists have debated whether this meant that Enceladus, with a diameter of only 500 kilometres, was hiding a reservoir of liquid water. It is one of about 60 moons orbiting the ringed planet Saturn.
Based on data collected last year by Cassini's Ultraviolet Imaging Spectrograph instrument, the researchers say the behaviour of the plumes supports a mathematical model in which the cracks that extend below the surface act as nozzles that channel water vapour from an underground liquid water reservoir.
The geysers continuously shoot plumes into space at more than 2160 kilometres per hour, say the researchers.
Close encounter
By using the instrument to observe the flickering light of a distant star as the geyser blocked its starlight, the researchers determined that the water vapour comes from narrow jets as it blasts into space.
"We're saying we detected these jets within the plumes and the gas moving at supersonic velocities. And we're saying that this is consistent with the previously developed model that has liquid water at depth" under the surface, says Hansen.
In March 2008, the Cassini spacecraft flew close over the surface of Enceladus and through a plume, collecting samples of ice and gas.
"There are only three places in the solar system we know or suspect to have liquid water near the surface - Earth, Jupiter's moon Europa and now Saturn's Enceladus," says Assistant Professor Joshua Colwell of the University of Central Florida.
"Water is a basic ingredient for life, and there are certainly implications there," says Colwell. "If we find that the tidal heating that we believe causes these geysers is a common planetary systems phenomenon, then it gets really interesting."
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