Does Enceladus Have an Ocean?

One of the more exciting placing in the Solar System seems to be a hitherto obscure moon of Saturn called Enceladus. Enceladus was found to emit a huge geyser of water and ice from its south pole by the Cassini space probe a few years ago.

Enceladus is about three hundred miles in diameter and orbits Saturn at a distance of about 112,000 miles. Superficially Enceladus resembles a lot of other rocky moons in our Solar System, a barren wasteland strewn with craters caused by billions of years of impacts.

But the discovery by Cassini of a huge geyser shooting up from the south pole of Enceladus has caused a heated debate among scientists about the origin of said geyser. Two studies, with seemingly contradictory results, have intensified that debate.

Simply put, does the geyser originate from a huge, sub surface ocean, heated by sub surface tidal forces caused by Enceladus being so close to Saturn, or does the geyser originate from evaporating ice? A study published in the journal Nature by Cassini scientists in Europe suggest the former. Another study, also published in Nature and conducted by scientists at the University of Colorado at Boulder, suggests the latter.

The University of Colorado study detected little or no sodium in the geyser shooting up from the south pole of Enceladus. This suggests that there is no liquid ocean beneath the surface of Enceladus that has been in contact with sub surface rocks, thus picking up minerals such as sodium.

The Cassini study detected sodium, not in the geyser, but in the E Ring or outer ring of Saturn, thought to have been created by the geyser shooting up from Enceladus. This study used data from Cassini as well as ground based telescopes on Earth. The Cassini study suggests that there is indeed a sub surface ocean, as salty and as warm as many of Earth's oceans.

Scientists are so far puzzled at the contradictory results of the two studies.

The presence of a sub surface, warm and salty ocean at Enceladus suggests the possibility of life existing below the surface of a moon of Saturn. The discovery of life, even microbial life, on another world has been the Holy Grail of planetary scientists since the dawn of the space age. Other places where such life might exist include Mars and Europa, a moon of Jupiter, which also is thought to contain sub surface oceans.

There are two proposals for follow up expeditions to moons of the Outer Planets, one to Europa, the other to Titan, the largest moon in the Solar System orbiting Saturn. But if a sub surface ocean exists beneath Enceladus, that moon may become a prime target for further scientific investigation.

Sources: Oceans in Enceladus? Scientists can't decide, World Science, June 24th, 2009

A "Briny Deep" Inside Enceladus?, Kelly Beatty, Sky and Telescope, June 24th, 2009