Saturnian moon inspires a gusher of questions

By Leonard David

Senior space writer

updated 2:19 p.m. ET April 3, 2006

BOULDER, Colo. - The discovery of apparent liquid water reservoirs erupting in Yellowstone-like geysers on Saturn’s moon Enceladus has produced a gusher of questions.

One leading unknown to solve: Could liquid water residing within a body so small and so cold provide comfort-level conditions suitable for living organisms?

NASA announced last month that high-resolution Cassini images of Enceladus show icy jets and lofty plumes that expel large quantities of particles at high speed. Scientists think the jets spout from near-surface pockets of liquid water, super-cold versions of the Old Faithful geyser in Yellowstone.

In the spring of 2008, Cassini is slated for another chance to look at Enceladus, flying within 220 miles (350 kilometers) of the perplexing moon. The end of Cassini’s "prime mission" is June 30, 2008, four years after arrival at Saturn.

The opportunity exists for placing Cassini in "extended mission" mode — but that’s only if financial resources allow.

Fueled by the spacecraft’s findings to date, attention is now turning to future observational roles of the interplanetary probe. One leading candidate is a sharper focus on astrobiology — even a "diving catch" to inspect in detail the makeup of those Enceladus plumes.

Cardinal goal
"After what we’ve discovered with Cassini, if we don’t get an extended mission, then there’s no hope for anybody," said Carolyn Porco, the Cassini imaging team leader based here at the Space Science Institute. The Cassini Imaging Central Laboratory for Operations, or CICLOPS, is the nerve center for the imaging team of the Cassini mission to Saturn.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

Cassini scientists should know a year from now whether or not Cassini will be given official approval for an extended mission. Then, within six months to a year after that, they will learn if the money is available to proceed beyond the nominal end of the mission, in mid-2008.

"In the meantime, we are planning for such an extension ... thinking about what it is we really want and need to do," Porco told Space.com. "Certainly, one of the cardinal goals of extending Cassini’s tour of the Saturnian environment would be further exploration of Enceladus," she said.

Microbes in the mix
Porco said Enceladus’ interior structure would be determined with close flybys designed to allow for such measurements.

"We would aim to fly very close over the south pole [of the moon] and through the jets and plume," Porco said, "in order to make more accurate measurements of the composition of the vapor and ice particles." Of course, how close Cassini can get to this action from Enceladus will be ultimately determined by spacecraft safety issues ... "but that would be the goal," she said.

And what about looking for microbes mixed in with those high-flying plumes?

"It’s not clear that Cassini has the means to determine if the ice crystals themselves contain microbes," Porco explained. "It may require a device with much greater compositional precision than we have, so that may have to be left for a future mission."

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