A Fizzy Ocean on Enceladus   
       
   January 26, 2011: For years researchers have been debating whether Enceladus,   
   a tiny moon floating just outside Saturn's rings, is home to a vast   
   underground ocean. Is it wet--or not? Now, new evidence is tipping the scales.   
   Not only does Enceladus likely have an ocean, that ocean is probably fizzy   
   like a soft drink and could be friendly to microbial life.   
       
   The story begins in 2005 when NASA's Cassini probe flew past Enceladus for a   
   close encounter.   
       
   "Geophysicists expected this little world to be a lump of ice, cold, dead, and   
   uninteresting," says Dennis Matson of NASA's Jet Propulsion Laboratory. "Boy,   
   were we surprised!"   
   [...]   
   A Cassini image of vaporous, icy jets emerging from fissures on Enceladus.   
   [more]   
       
   Cassini found the little moon busily puffing plumes of water vapor, icy   
   particles, and organic compounds out through fissures (now known as "tiger   
   stripes") in its frozen carapace. Mimas, a nearby moon about the same size,   
   was as dead as researchers expected, but Enceladus was precociously active.   
       
   Many researchers viewed the icy jets as proof of a large subterranean body of   
   water. Near-surface pockets of liquid water with temperatures near 32øF could   
   explain the watery plumes. But there were problems with this theory. For one   
   thing, where was the salt?   
       
   In initial flybys, Cassini's instruments detected carbon, hydrogen, oxygen,   
   nitrogen, and various hydrocarbons in the plume gasses. But there were none of   
   the elements of salt that ocean water should contain.   
   [...]   
   "Tiger stripes" on Enceladus. [more] In 2009 Cassini's cosmic dust analyzer   
   located the missing salt - in a surprising place.   
       
   "It wasn't in the plume gasses where we'd been looking for it," says Matson.   
   "Instead, sodium and potassium salts and carbonates were locked up in the   
   plumes' icy particles.* And the source of these substances has to be an ocean.   
   Stuff dissolved in an ocean is similar to the contents of these grains."   
       
   The latest Cassini observations presented another intriguing discovery:   
   thermal measurements revealed fissures with temperatures as high as -120ø   
   Fahrenheit (190 Kelvin).   
       
   "This discovery resets our clocks!" says Matson. "Temperatures this high have   
   to be volcanic in origin. Heat must be flowing from the interior, enough to   
   melt some of the underground ice, creating an underground waterworks."   
       
   The finding has led the scientists to ponder how contents of an ocean capped   
   by a crust of ice as much as tens of miles thick could reach the surface.   
       
   "Have you ever been sprayed when you popped the top of a soda can?" asks   
   Matson.   
       
   The model he and his colleagues propose suggests that gasses dissolved in   
   water deep below the surface form bubbles. Since the density of the resulting   
   "sparkling water" is less than that of the ice, the liquid ascends quickly up   
   through the ice to the surface.**   
       
   "Most of the water spreads out sideways and 'warms' a thin surface ice lid,   
   which is about 300 feet thick," explains Matson. "But some of it collects in   
   subsurface chambers, builds up pressure, and then blasts out through small   
   holes in the ground, like soda spewing out of that can you opened. As the   
   remaining water cools, it percolates back down to replenish the ocean and   
   start the process all over again."   
   [...]   
   A close-up view of a Tiger stripe on Enceladus obtained by Cassini in 2008.   
   Does a fizzy ocean lie underneath? [more]   
       
   Another mystery remains: "Where's the heat coming from on this tiny body?"   
   wonders Larry Esposito of the University of Colorado. "We think tidal heating   
   could be contributing."   
       
   Saturn's powerful tides actually cause the shape of Enceladus to change   
   slightly as it orbits. Flexing motions in the moon's interior generate   
   heat--like the heat you feel in a paperclip when you rapidly bend it back and   
   forth. In this model, internal friction powers volcanic activity, which warms   
   and melts the ice.   
       
   "It's clear now that, whatever is producing the heat, Enceladus meets many   
   requirements for life," says Esposito. "We know it has a liquid ocean,   
   organics, and an energy source. And to top it off, we know of organisms on   
   Earth in similar environments."   
       
   No one knows for sure what's going on under the ice, but it seems this little   
   moon has quite a story to tell: erupting jets, an underground ocean, the   
   possibility for life.   
       
   And they thought this place was dull.   
       
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   The Cassini-Huygens mission is a cooperative project of NASA, the European   
   Space Agency and the Italian Space Agency. JPL, a division of the California   
   Institute of Technology in Pasadena, Calif., manages the mission for NASA's   
   Science Mission Directorate, Washington, D.C.   
       
   *Cassini's Cosmic Dust Analyzer Principal Investigator Ralf Srama of the Max   
   Planck Institute for Nuclear Physics in Heidelberg, Germany, led the study.   
       
   **In their 1988 study of Europa, Crawford and Stevenson introduced the term   
   "Perrier Ocean" for this model. See G. D. Crawford, D. J. Stevenson, Icarus,   
   73, 66-79 (1988).   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.59   
    * Origin: NCS BBS (1:3828/7)