Archive: Enceladus Eruptions Reported (2005)

We were among the first to announce the geysers found on Enceladus.

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Enceladus Eruptions Caught on Camera    11/28/2005
Enceladus, one of the small icy moons of Saturn, is undergoing eruptive activity right now. Evidence from previous flybys has now been corroborated visually in stunning images that made the lead stories on NASA, JPL and Cassini.  Amateur enthusiasts were already expressing excitement at the images before the announcement (see Unmanned Spaceflight). The complete set of raw images is available at the Cassini Raw Image Gallery and a trio of images was published by the Cassini Imaging Team.

The images show several distinct jets of material being emitted from the limb, as viewed in back lighting. There might be a dozen or more. [Later images showed more than a hundred.] All appear aligned along fractures in the crust. The material is most likely water ice. [Some salts and minerals were later identified in tiny amounts.] Particles are apparently being ejected with sufficient force to escape straight out; no ballistic umbrella-shaped paths, as with Io’s volcanos, is evident with these eruptions from Enceladus, though it must be remembered that Enceladus, being smaller and less massive, has a much lower escape velocity. The plumes reinforce long-held suspicions that Enceladus is supplying the material to Saturn’s E ring.

Eruptive activity was inferred during the March and July encounters from magnetic field, dust particle and ultraviolet sensors (see 08/30/2005 story). The emissions at the time were found to be localized at the south pole in a field of long, parallel canyons dubbed the “tiger stripes.” These new visual images line up perfectly with that region. Now that the plumes are clearly visible, scientists have compared them with limb images from the plume-hunting observations January 16. Though tantalizing hints of plumes were seen, scientists were cautious to accept them as real, not knowing if they were imaging artifacts. Since those line up with the new ones, Enceladus has probably been in a continuous state of eruption most of this year, probably far longer.

Further measurements will be required to determine if the activity is episodic or continuous. The discovery will spur additional questions about the composition of the particles, their size distribution, the volume ejected over time, the mechanism of ejection, and why it occurs only in the south polar region. The biggest puzzle of all seems to be why this moon, much smaller than Io and not in any orbital relationship with Saturn or other large body sufficient to cause tidal heating, should be so active. Intuitively, a body this small should be dead cold. Any internal heat from the moon’s formation should long ago have dissipated, if this body is as old as commonly believed. Nor could solar heating explain this, as in the case of Triton’s faint nitrogen geysers, which coincided with the angle of greatest sunlight. Enceladus receives most of its illumination at the equator, not the poles. Clearly something interesting is going on down south on this little moon. Today’s discovery will likely motivate NASA scientists to add more Enceladus encounters to a likely extended mission, after the prime mission ends in July, 2008.

Here is prima facie evidence that Enceladus is young. The burden of proof is on the moyboys (9/16/2005 commentary) to prove otherwise. The E ring has been known for over 20 years and is composed of particles so small (micron sized), it must be continuously replenished or it would disappear within decades. Does this mean that these Enceladus geysers have been erupting continuously for decades, centuries, millennia? How can it be credible to believe this kind of process can run for millions or billions of years? Everyone can enjoy the discovery of a new Yellowstone. Those open-minded to allow for far younger ages of solar system objects have the added entertainment of watching the moyboys scramble with each new eruption. Maybe the new plume should be called the Fountain of Youth.

News from the Solar Neighborhood    11/28/2005
Here’s a collection of recent items of interest under the sun.  (Don’t miss the big story above, too.)

• My Rhea Lies Under the Spacecraft:  Cassini added another trophy to its moon collection Saturday, skimming just 300 miles above the surface of Saturn’s large moon Rhea. (Saturday is named after Saturn, hey). Rhea is the largest moon after Titan, and one of two (along with Dione) remembered from Voyager days as having wispy or feathery streaks on its leading hemisphere. Now that Cassini has gotten in for a closer look, scientists found that the streaks are not frost deposits as formerly thought. Instead, they are regions of sharp cliffs exposing bright water ice. Rhea also has a prominent fresh-looking rayed crater. Though made of ice, the surfaces of Saturn’s moons are frozen so hard, the ice has the properties of hard rock. Impacts produce craters, therefore, very similar to those on our moon, complete with central peaks, rays and ejecta blankets. The Cassini Imaging Team has put together a gallery of the best raw images; the complete set is available on the Cassini Raw Image Database.
• Spiral Ring:  Saturn’s F-ring is one long spiral, according to an international team that proposed the new theory in Science (see report on Space.com and click link to the artist’s conception). If so, this raises lots of new questions. Prometheus and Pandora, long thought to shepherd the ring particles into the narrow ringlets, may actually act more like attack dogs. The ring appears tenuous and dynamic. The spiral structure appears unique, with no clear explanation leaping out of the data about how the spiral is generated and maintained.
• Japan Mines an Asteroid: The Falcon (Hayabusa) successfully gathered samples of asteroid Itokawa (see Planetary Society report). This gives the fledgling Japanese space agency a first, especially if the samples are successfully returned in 2007 at The Outback (not the restaurant, but the real Aussie wasteland, out back and down under). The asteroid appears to be a rubble pile of loosely-cohering material with few craters. Though it visited a different type of object – a comet – Stardust will hit the tape first on January 15 when its samples parachute into the Utah desert. Hopefully it will not make a crater like Genesis did.
• Mars with Spirit:  The Mars Exploration Rover imaging team released a blockbuster to celebrate Spirit’s first “Martian Year” anniversary in Gusev Crater, complete with special effects. If you wonder how Spirit was able to take a picture of itself in the distance, well, that’s Hollywood.
• Next Mars Champ Doing Fine:  The hefty Mars Reconnaissance Orbiter, affectionately known as “Mr. O,” is halfway there. Already, Mars Express seems a hard act to follow, but when MRO goes into orbit next March, its best-ever cameras and instruments are slated to send back more data than all previous missions combined.  Till then, we hear Opportunity, Mars Odyssey, and Mars Global Surveyor hollering, “Hey, don’t forget me!”

These are great days of exploration. At this time 200 years ago, Lewis and Clark were settling in at Fort Clatsop for a long winter. At this time 100 years ago, Percival Lowell was squinting eagerly through his Lowell Observatory eyepieces, imagining cities and exotic inhabitants on Mars. In such a short time, look what their country – their world – has done. Space exploration did not evolve. It is a demonstration of the power of intelligent design to order and direct natural materials toward purposeful ends.

As a member of the Cassini team at JPL, it was thrilling to be among the first to see the images of the Enceladus geysers and many other phenomena in the Saturn system.

First close views of Saturn’s rings, JPL, July 1, 2004. Photo by David Coppedge

Bonnie Buratti, lower left, among Cassini scientists watching close-up images of Enceladus arrive on March 9, 2005. Photo by David Coppedge