Possible water ocean
In late 2008, scientists observed water vapor spewing from Enceladus's surface. This could indicate the presence of liquid water, which might also make it possible for Enceladus to support life.[57] Candice Hansen,[58] a scientist with NASA's Jet Propulsion Lab, headed up a research team on the plumes after they were found to be moving at ~2,189 kilometers per hour (1,360 miles per hour). Since that speed is unusual and is usually attained when water is involved, they decided to investigate the compositions of the plumes.[59]
Eventually it was discovered that in the E-ring about 6% of particles contain 0.5–2% of sodium salts by mass, which is a significant amount. In the parts of the plume close to Enceladus the fraction of "salty" particles increases to 70% by number and >99% by mass. Such particles presumably are frozen spray from the salty underground ocean. On the other hand, the small salt-poor particles form by ****genous nucleation directly from the gas phase. The sources of salty particles are uniformly distributed along the tiger stripes, whereas sources of "fresh" particles are closely related to the high-speed gas jets. The "salty" particles move slowly and mostly fall back onto the surface, while the fast "fresh" particles escape to the E-ring, explaining its salt-poor composition.[60]
The "salty" composition of the plume strongly argues that its source is a subsurface salty ocean or subsurface caverns filled with salty water.[61] Alternatives such as the clathrate sublimation hypothesis can not explain how "salty" particles form.[60] Additionally, Cassini found traces of organic compounds in some dust grains.[60] Enceladus is therefore a candidate for harboring extraterrestrial life.[62]
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Originally Posted by David Jamieson
