Tidal forces pinpointed as catalyst for Enceladus' eruptions

Tidal forces pinpointed as catalyst for Enceladus' eruptions
Cassini image of Enceladus' southern poll
Cassini image of Enceladus' southern poll
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Cassini image of Enceladus' southern poll
Cassini image of Enceladus' southern poll

Researchers from the University of Chicago and Princeton University have generated a new computer model that successfully simulates themechanism driving impressive geyser eruptions observed taking placeon the Saturnian moon Enceladus. The geysers have been active sinceCassini first observed the phenomena in 2005, and were likelyerupting long before the probe entered orbit around Saturn.

Enceladus has served asthe focal point of repeated observation over the course of Cassini'sprolonged mission characterizing Saturn and her moons. Yet, in spiteof the generous attention paid to the moon, the mechanism that drivesof the icy body's impressive geysers has remained a mystery.

These geysers spewforth vast quantities of frost and vapor from vast rents, or "tigerstripes" in the moon's south polar region. Furthermore, thesubsurface ocean believed to be buried beneath Enceladus' icyexterior is considered one of the most likely places in our solarsystem to discover the presence of alien life.

In an attempt to gain abetter understanding of the materials cast out by Enceladusimpressive cryovolcanoes, the Cassini spacecraft dived throughone of Enceladus' plumes last year in the search of clues as towhether the environment beneath the surface of the seemingly barrenmoon is hospitable to life.

The constant nature ofthe eruptions has given rise to a number of questions. For example,how have the geysers managed to operate continuously for over adecade without being sealed atleast temporarily by a build-up of frost particles choking theentrances of the shafts?

Anotheranomaly has been observed wherein eruptions fail to achieve theirpeak activity until roughly five hours after the expected time, basedon tidal response models. One theory attempted to explain awaythe lag by asserting that Enceladus boasted a spongy shell that tooklonger than anticipated to react to the tidal pressures exerted onthe icy body by the nearby gas giant.

The researchers createda computer model of Enceladus, complete with a series of parallelslots located at the observed eruption sites that extended from thesurface of the moon down to its underground ocean.

This model was thensubjected to the tidal forces generated by Saturn's gravity as itinteracts with the moon's interior. Tidal pumping in the slots causesturbulence, heating the water contained within. However, the activitydid not occur all at once in the new model, with the key variable ineruption timing proving to be the diameter of the separate parallelshafts.

The influence of thegas giant's gravity on water in narrow shafts led to an eruption upto eight hours after the predicted peak level of activity, whilewider shafts respond much faster. The sweet spot in between these twoextremes creates an eruption with a five-hour delay, explaining thelag observed by the Cassini spacecraft.

According to theresearchers, their model could be tested against the new datacollected by Cassini during its recent flyby of Enceladus. If theheat driving the plumes is in fact being generated from deep withinthe vents by tidal pumping, then the surface of the south polarregion between the vents would register as cold in the Cassini data.

Source: The University of Chicago

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