Scientists explain big vapor plume on Saturn moon

By Michael Kahn

LONDON (Reuters) - Scientists on Wednesday said they have an explanation how one of Saturn's moons can spew out a giant plume of water vapor, adding to evidence a source of life -- water -- lies beneath the moon's frozen surface.

Using a computer model, German researchers showed the temperature at the bottom of surface cracks on Enceladus has to be about 0 degrees Celsius, the so-called triple point of water where vapor, ice and liquid water all can coexist.

"This makes this moon very interesting for further study because there is a connection between liquid water and life," Sascha Kempf, a physicist at the Max Planck Institut in Heidelberg, said in a telephone interview.

"This is the kind of thing planetary scientists hope for."

The scientists published their findings in the journal Nature.

Mars, Jupiter's moon Europa and Enceladus are the only places in the solar system with direct evidence of water. Finding organisms different from those on Earth may provide scientists with answers to questions ranging from where diseases come from to how our sun and planets formed more than 4.5 billion years ago.

Scientists have taken an especially close look at Enceladus because it seems to have a smooth surface -- suggesting recent geological activity that, in turn, could mean liquid water.

They are also intrigued by the plume itself, a gigantic geyser of water vapor and tiny ice particles. One mystery was how the dust particles slowed down to keep the plume restrained by the gravity of the moon, said Kempf, who worked on the study.