CICLOPS: Cassini Imaging Central Laboratory for OPerationS
Captain's Log
March 26, 2008

Diving Over Enceladus

Our run of daring tactical maneuvers over the surface of Enceladus to uncover as much as we can about this strange beast began two weeks ago, and today we learn what came of that encounter. On March 12, we flew within a mere 50 km (~ 30 miles) over the equatorial region of the moon, approaching from the north and then departing towards the south, with passage through the moon's famous south polar plume. This very low altitude is about one seventh (1/7) the distance that the International Space Station flies above the Earth and is the closest we've flown yet to any object in the Saturn system.

And it went spectacularly well.

The information collected by several instruments on board our ship has significantly enhanced what we already know about Enceladus' south polar environment and the story has grown ever more thrilling.

For starters, the instrument capable of sniffing the plume's composition has hit the jackpot in affirming previously uncertain indications that organic materials, heavier and more complex than methane, are present in the vapor that emerges with the visible jets. The sub-surface sources of Enceladus' dramatic geological activity are beyond doubt rich in astrobiologically interesting materials.

We also now clearly see that the majority of the heat radiating from the south polar terrain does indeed emanate from its tiger stripe fractures and that the hottest locales are not mere spots, but substantial linear segments of several fractures. These new findings have confirmed the prediction, made from our images of the polar jets, that new hotter-than-average regions would be found and that all observed jets would be coincident with excess warmth. We imaging folks are feeling pretty good right now.

And most exciting of all: the highest temperatures now measured are about 180 Kelvins, some 63 degrees Fahrenheit warmer than estimated from previous measurements. Though by no means a guarantee, these results make the possibility of liquid water close to the surface of the moon even more likely. Sacre bleu!

There is still so much more to learn, and a great deal more analysis to be done of the information already in hand and that expected from future Enceladus flybys, before we can be confident that organic-rich, liquid water reservoirs are truly the sources of the moon's dramatic geologic activity. Maybe we'll never know from Cassini alone, and the answer may require a return to the Saturn system with a spacecraft suitably equipped to address this fascinating question.

But there is enough encouragement in Cassini's new results to keep us breathlessly awaiting our next visit to Enceladus in August, when planned extremely high resolution images of the fractures may reveal if there is anything morphologically distinct and telling about the places where Enceladus' towering jets emerge from its interior. Five months from now, we may know the answer.

Five months .... seems like an eternity.

Carolyn Porco
Cassini Imaging Team Leader
Space Science Institute
Boulder, CO

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