Water blasted out of geysers on the Enceladus south pole, thousands of kilometers into space. Image was taken by the Cassini space probe. Credit: NASA.

Saturn’s icy moon Enceladus does have a lot in common with the more famous “icy moon” Europa orbiting Jupiter. Both are believed to be covered by ice with a possibility of vast oceans beneath.

It has previously been observed that Enceladus seems to spew water from large geysers out into space. This water also seems to contain salt, and since salt lowers the freezing point of water, this suggests that there might be liquid water beneath the icy surface.

The geysers appear to be especially abundant on the moon’s south pole, within an area of active fissures known as “tiger stripes”. Now a team of scientist has presented a probable explanation to what might cause these fissures to spew water out into space.

The findings have been published in Nature and the suggested explanation for the fissures are Saturn’s gravitational pull. The team observed that the plumes were brighter when Enceladus was furthest from Saturn, and therefore the planet evidently affects them

Since Enceladus has an elliptical orbit, rather than a circular. This causes the moon to be pulled and squeezed by the immense gravity of Saturn, heating it’s interior and creating geological activity.

The scientists used images gathered by the Cassini spacecraft, and these provide clear evidence that the plumes change with the moon’s position in its orbit.

Matthew Hedman at the Cornel University is the lead author of the study, he writes “the plume was much brighter when it was furthest from Saturn than when it was closest to the planet”. “Previous models predicted that when Enceladus was near the point most distant from Saturn, the cracks would be pulled open or widened, and the most amount of liquid would escape. This is the first observational data we have that shows quite clearly that is the case.”

With these discoveries on Enceladus, it has certainly become one of the most promising places in our solar system to look for life. Anywhere where there is a presence of liquid water the chance for life, as we know, does certainly increase dramatically. And unlike Europa, also believed to have liquid water beneath several kilometers of ice, Enceladus should have liquid water on both its surface and beneath its thick ice cover.

An observed correlation between plume activity and tidal stresses on Enceladus