A computer model may tell scientists a bit more about the sustained eruptions that take place on the icy moon of Saturn. Researchers have learned how tidal stresses may be responsible for Enceladus' long-lived eruptions.
"On Earth, eruptions don't tend to continue for long," said Edwin Kite, one of the researchers. "When you see eruptions that continue for a long time, they'll be localized into a few pipelike eruptions with wide spacing between them."
Enceladus most likely has an ocean underlying its icy surface. Somehow, the moon has managed to sprout multiple fissures along its south pole. These stripes along the surface have been erupting vapor and frost particles for decades along their entirely length; in fact, researchers believe that these eruptions have been occurring for much longer than usual.
"It's a puzzle to explain why the fissure system doesn't clog up with its own frost," Kite said. "And it's a puzzle to explain why the energy removed from the water table by evaporative cooling doesn't just ice things over."
In this case, the moon needs an energy source in order to balance the evaporative cooling. But the researchers needed to test this in order to see if it was a viable theory or not.
"The only tricky part is calculating the elastic interactions between the different slots and the varying water level within each slot as a response to the tidal tress," said Kite.
The width of slots affects how quickly they can respond to the tidal forces. With wide slots, the eruptions respond quickly to tidal forcing. With narrow slots, though, the eruptions occur eight hours after the tidal forces reach their peak.
In between these is a spot when tidal forces turn water motion into heat. This generates enough power to produce eruptions that match the five-hour lag.
"If the new mechanism is a major contributor to the heat coming from the fractures, then the south polar ice in between the fractures may in fact be cold," said Carolyn Porco, one of the researchers. "The jury is still on out on this until the results from the final Enceladus flybys of last year are fully analyzed."
The findings are published in the journal Proceedings of the National Academy of Sciences.
