It is all in the wobble.
After analyzing seven years worth of imagery taken of Saturn’s tiny moon Enceladus, scientists with NASA’s Cassini mission have discovered a small but clear sign that it wobbles slightly during orbit of its host planet. Such an observation can only be explained by the motion of a vast underground ocean, explained officials at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, in a statement.
The finding also suggests that the plumes of water and organic molecules observed spraying from fractures close to Enceladus’ south pole are coming from this enormous body of liquid water.
Details of the discovery appear online this week in the journal Icarus.
“This was a hard problem that required years of observations, and calculations involving a diverse collection of disciplines, but we are confident we finally got it right,” says lead author Peter Thomas, a Cassini imaging team member at Cornell University, in Ithaca, New York, in the JPL statement.
“If the surface and core were rigidly connected, the core would provide so much dead weight the wobble would be far smaller than we observe it to be,” says co-author Matthew Tiscareno, a Cassini participating scientists at the SETI Institute in Mountain View, California. “This proves that there must be a global layer of liquid separating the surface from the core.”
Scientists cannot yet explain what has prevented the moon’s ocean from freezing. One possibility is that tidal forces created by Saturn’s gravity could be generating enough heat within Enceladus to maintain the water in a liquid state. Another is that high levels of ammonia present in observed water plumes could act as a kind of antifreeze
Enceladus is a tiny world, with a diameter of only 314 miles (505 kilometers). Because Cassini has detected plumes of water vapor rising off the moon’s surface containing organic molecules and complex chemicals, many believe it holds great promise as a place where extraterrestrial life could flourish.