New data from NASA's Cassini proves that the intensity of the jets of water ice and organic particles that shoot out from Saturn's moon Enceladus depends on its proximity to the ringed planet, offering further evidence that some kind of body of water is trapped beneath its surface.
For years scientists hypothesized that the intensity of the jets varied over the time, but until now no one had been able to point to any recognizable pattern.
Led by Matt Hedman, a Cassini team scientist based at Cornell University, the researchers discovered that the plume was dimmest when Enceladus was closest in its orbit to Saturn and gradually brightened until it reached its farthest point, at which point it exploded at a rate three to four times brighter than the dimmest detection.
Applying this discovery to previous models of how Saturn squeezes the moon, the researchers deduced that the stronger gravitational squeeze near the planet reduces the opening of the fissures, restricting the amount of material able to squeeze its way out, and vice versa.
"The jets of Enceladus apparently work like adjustable garden hose nozzles," Hedman explained in a press release. "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."
And just as water from a hose is derived from a much larger source, the researchers posit that the same may be true in the case of the moon's jets.
"The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water," said Christophe Sotin, a co-author and Cassini team member at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif.
And this, Sotin says, would be exciting because where there is liquid water, life may exist.
Cassini, whose visual and infrared mapping spectrometer (VIMS) offered the data for this study, has been orbiting Saturn since 2004, gathering information on a wide range of subjects, including the hydrocarbon composition of the surface of Saturn's moon Titan and the seismological signs of Saturn's vibrations in its rings.
"Cassini's time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are," said Linda Spilker, Cassini project scientist at JPL. "We've come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our solar system formed."