Enceladus Eruptions Caught on Camera

first_imgEnceladus, 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.  All appear aligned along fractures in the crust.  The material is most likely water ice.  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 (09/16/2005 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.(Visited 8 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img