Since NASA’ Cassini spacecraft observed the famous geysers erupting on Saturn’s moon Enceladus in 2005, the phenomena that drives and sustains these eruptions has baffled scientists, but now researchers may have finally solved the mystery.
Enceladus is a relatively small body, the sixth-largest moon of Saturn, only a bit over 500 kilometers (310 mi) in diameter. In 2005, the Cassini spacecraft started multiple close flybys of Enceladus revealing its surface in greater detail. One of the biggest discovery was the observation of water-rich plumes shooting out from it’s south polar region. This mean that Enceladus is geologically active today, some scientists even think that it most likely has an ocean underlying its icy surface. But what was puzzling is the mechansim behind these plumes.
It’s a puzzle to explain why the fissure system doesn’t clog up with its own frost,
said Edwin Kite.
And it’s a puzzle to explain why the energy removed from the water table by evaporative cooling doesn’t just ice things over.
Now, scientists from the University of Chicago and Princeton University have identified a mechanism which may tell us a bit more about the mechanism behind these impressive geysers.
Cassini data have strongly indicated that the cryovolcanic plumes of Enceladus probably originate in a biomolecule-friendly oceanic environment,
the researchers said.
One of the problems that attracted our attention was the anomalous tidal response of the Enceladus eruptions.
First, scientists thought these geysers were generated due to the tidal forces — the same kind responsible for the tides on Earth — exerted on the moon by Saturn. But a close analyze showed the eruptions reach their peak 5 hours later than would be expected if they were caused by a simple tidal force. What was also puzzling is these eruptions continue for a long time. And why don’t the eruptions frost over or freeze over?
The new model explains all of those questions and more. Saturn’s gravitational pull is what causes the “tiger stripes” on Enceladus. Those same tidal forces are likely sloshing the ocean deep in the moon. As that water flows in and out of the slots proposed in the new model they generate heat, powering the lagging eruptions.
In that crack you have strong tidal flow, so it would be interesting to see what a real ice sheet does in an environment that’s analogous in terms of the amplitude of the stresses and the temperatures of the ice,
Professor Kite said.
The new study is published in the journal Proceedings of the National Academy of Sciences.