Saturn holds a tiny secret
Icy chasms on one of Saturn's moons may be a hiding place for alien life.
July 23, 2007— -- Icy chasms on one of Saturn's most humble moons, hidden amid its glorious rings, have overtaken the sands of Mars and the stratosphere of Venus as the most intriguing potential hiding place for alien life in our solar system.
Enceladus, a shining ball of ice hugging Saturn's rings, was first caught in the act of spewing a watery geyser from its south pole two years ago by the international Cassini mission. Water, life's most crucial ingredient, was blasting 270 miles into space, actually hitting the orbiting spacecraft, from cracks on the frozen moon dubbed "tiger stripes."
Astronomers and astrobiologists, who are always looking for signs of life far from Earth, were caught by surprise — and they remain so, unable to explain how such a small celestial body (only 318 miles wide at its equator ) can pump out so much water.
"Nobody has figured it out," says Andrew Dombard of Johns Hopkins University's Applied Physics Laboratory in Laurel, Md. "Enceladus has jumped to the top of astrobiologists' list for a mission."
And as for the big question — Does life exist there? — the answer is the same: Who knows?
The most recent Cassini flyby of Enceladus, a distant one at 55,000 miles, was on June 28. Each such visit has heightened the interest of planetary scientists, who have erupted with their own flurry of theories, including two reports published in the journal Nature in May.
"Probably with 20/20 hindsight, we can say we expected something from Enceladus," says Cassini scientist Jonathan Lunine of the University of Arizona in Tucson. He notes that since the Voyager missions flew past Saturn in the early 1980s, the moon has been known as the brightest object in the solar system because of its coating of fresh ice.
But the eruption of the geyser from the moon's south pole rather than from the equator, which is subject to the strongest gravitational pull from Saturn, and the curious tiger-stripe vents, cracks about 80 miles long, were "a big surprise," Lunine says. "These are very exotic kinds of features."
Every eight seconds, the geyser spotted in a flyby of Enceladus in December 2005 dumped about a ton of not just water but also a mixture of life's building blocks — organic compounds such as methane, propane, acetylene and carbon dioxide, as well as nitrogen —
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