A ghostly apparition has long been known to follow Saturn moon Enceladus in its orbit around the gas giant. But until now, scientists have had a hard time tracking its source.
Using images from NASA's Cassini mission, the source of these tendrils have been tracked down and they originate from the icy moon's famous geysers. But even better than that, scientists have been able to track the specific tendril shapes down to the specific geysers that produce them.
PHOTOS: Enceladus: Saturn's Snowball Ocean Moon
"We've been able to show that each unique tendril structure can be reproduced by particular sets of geysers on the moon's surface," said Colin Mitchell, a Cassini imaging team associate at the Space Science Institute in Boulder, Colo., and lead author of a paper published int he Astrophysical Journal.
Mitchell's team combined the high-resolution Cassini data with computer simulations to track the trajectories of the ice grains to individual geysers blasting through giant fissures in Enceladus' icy crust. Consisting of tiny ice particles, dust and organic molecules, the geysers provide a tantalizing view into the components of the sub-surface ocean that is theorized to exist below the moon's thick icy crust.
From Enceladus, these huge features reach tens of thousands of miles away into Saturn's E ring, supplying it with icy particles. The researchers were able to deduce the size of the ice particles in the E-ring and the tendrils, measuring them to "no smaller than about a hundred thousandth of an inch," according to a NASA news release. This provided a direct link from Enceladus' geysers to one of Saturn's outer rings.
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Throughout Cassini's studies of Enceladus' tendrils, variations in their shape and size have become apparent, probably due to the tidal squeezing regulating the icy output from the moon's contracting and expanding fissures. Further work is needed to verify this correlation, however.
A cool implication of this work is that understanding the dynamics of Enceladus' tendrils may provide an accurate measure on how ice is leaving the small moon and how much is making it to the E ring. This, in turn, may help planetary scientists understand the lifetime and evolution of Enceladus' sub-surface ocean.
"As the supply lanes for Saturn's E ring, the tendrils give us a way to ascertain how much mass is leaving Enceladus and making its way into Saturn orbit," said Carolyn Porco, team leader for the imaging experiment and a coauthor on the paper. "So, another important step is to determine how much mass is involved, and thus estimate how much longer the moon's sub-surface ocean may last."
ANALYSIS: Saturn's Moon Enceladus Has Underground Ocean
As Cassini's mission is drawing to a close, Enceladus is being singled out as an important target for the spacecraft to continue to study. Along with a growing number of outer solar system moons, the nature of Enceladus and its ocean raises key questions about the possibility of life beyond Earth, so further studies of these ghostly tendrils and the moon's extensive array of geysers are planned.