Cassini to make important fly by of Enceladus this weekend

Enceladus has recently become my favorite object in the solar system. The tiny, icy moon of Saturn has revealed so many surprises in just the last few years, and I'd wager it's got a few more shockers in store.



The moon of Saturn, once believed to be cold and dead, has become one of the strongest candidates to harbor extraterrestrial life that we know of. Small bodies without atmospheres at this distance from the sun are usually dead, yet something very interesting is going on under the ice of Enceladus' south pole. Cassini should be able to tell us a lot more on its next pass, coming up November 30th. Universe today has a better write up about it than I could manage, so check that out for details.

Here's the short story: it appears that a combination of tidal heating caused by the pull of Saturn and other moons combined with radioactive heating in Enceladus' core might be sustaining a subsurface ocean of liquid, salty water. The great thing about Enceladus compared to the other potential habitable sites in the solar system is that Enceladus is spewing the evidence right into space, in the form of geysers erupting from the south pole. The plumes from these geysers achieve amazing speeds of over a 1,300 miles an hour, easily fast enough to escape and contribute to Saturns E ring. Cassini has already flown through the plumes several times and analyzed their content, revealing lots of H20, salt, and ammonia, but the each flyby reveals more and more about the subsurface world of Enceladus.

Cassini's latest flyby will once again use spectrometry to analyze the content of the plumes, as well as radio instruments to help understand the gravitational dynamics of the tiny moon, perhaps leading to a better picture of the subsurface oceans. Determining the composition of the plumes will tell us a lot about what kind of heating mechanisms need to be involved. For instance, a high ammonia content would greatly lower the melting temperature of water and thus less heat would be needed to sustain a liquid ocean.

Keep in mind that Cassini was not designed to probe for signs of life on Enceladus, but what it finds might just coax NASA into designing a specific mission.

What I really love about Enceladus is how it has forced us to rethink habitable zones. Even if Enceladus doesn't have life in its subsurface oceans, the fact remains that the mechanisms exist to support life on cold, icy moons and planets. If tidal heating combined with the natural radioactive heating (found in the core of most planets) is enough to sustain a liquid ocean, what's to stop us from considering even extrasolar planets as harbingers of life, i.e. rogue planetary systems adrift in space, not orbiting any star?

The more we look, the more hospitable the universe seems!