Saturn’s moon Enceladus is back in the news at the Division of Planetary Sciences meeting at Cambridge University this week. Not that it has ever quite left the spotlight since 1981; that’s when Voyager 2 photographs told scientists that parts of the moon had been geologically active as recently as 100 million years ago. The moon’s smooth terrain was hard to explain — how does an object 314 miles across get hot enough to melt?
Then Cassini came and Enceladus’ wonders increased. We now know that the moon has an atmosphere of water vapor, nitrogen, carbon dioxide and other organic (i.e., carbon-based) molecules concentrated at its south pole. Moreover, that polar region is hotter than expected, -183 degrees Celsius vs. -203 Celsius as predicted by the models, and is marked by 80-mile long parallel cracks that vent vapor and ice particles. Some of this material may have crystallized on the surface as recently as the past decade.
At the Cambridge meeting, Robert H. Brown (University of Arizona), leader of the Cassini visual and infrared mapping spectrometer team, said the geological activity on Enceladus is probably driven by liquid water beneath the surface. Brown went on to note that his team had detected not just carbon dioxide but methane, ethane and ethylene in the cracks (now dubbed ‘tiger stripes’). And here’s the kicker, From a University of Arizona press release:
“So you’ve got subsurface liquid water, simple organics and water vapor welling up from below. Over time — and Enceladus has been around 4.5 billion years, just like Earth and the rest of the solar system — heating a cocktail of simple organics, water and nitrogen could form some of the most basic building blocks of life,” Brown said. “Whether that’s happened at Enceladus is not clear, but Enceladus, much like Jupiter’s moon Europa and the planet Mars, now has to be a place where we eventually search for life.”
It’s now thought that icy material from Enceladus is a major source of the particles that replenish Saturn’s outermost ring, the E ring. Brown believes the methane locked up inside the moon has probably been there since the Solar System formed.
Image: A false-color Cassini view of Enceladus, taken July 14, 2005. Note the south polar region at lower right, with its tectonic gashes, the source of ice particle venting that may supply material to Saturn’s outermost ring. Credit: NASA/JPL/Space Science Institute.
Centauri Dreams‘ take: back in the days when Project Orion was mapping out ways to get to Saturn (as ably told in George Dyson’s Project Orion: The True Story of the Atomic Spaceship), one of the team’s project targets was Enceladus because of the amount of water ice suggested by its reflectivity. Imagine what surprises Orion would have found if it ever flew, and what further surprises we’re likely to find as Cassini and later instruments continue this investigation. The next Cassini flyby is scheduled for March 12, 2008.
