NASA's Cassini spacecraft has found that the intensity of jets of water ice and organic particles that shoot out from Saturn's moon Enceladus depends on the moon's proximity to the ringed planet.
The finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon.
This is the first clear observation the bright plume emanating from Enceladus' south pole varies predictably.
"The jets of Enceladus apparently work like adjustable garden hose nozzles," Matt Hedman, the paper's lead author and a Cassini team scientist based at Cornell University in Ithaca, N.Y, said.
"The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away. We think this has to do with how Saturn squeezes and releases the moon with its gravity," he said.
Cassini, which has been orbiting Saturn since 2004, discovered the jets that form the plume in 2005. The water ice and organic particles spray out from several narrow fissures nicknamed "tiger stripes."
"The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water," Christophe Sotin, a co-author and Cassini team member at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, said.
"Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present," he said
For years scientists hypothesized the intensity of the jets likely varied over time, but no one had been able to show they changed in a recognizable pattern.
Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini's visual and infrared mapping spectrometer (VIMS), and looking at data gathered over a long period of time.
The findings are published in the journal Nature. (ANI)