Cassini’s Cameras Hit the Target

Imagine flying all the way out to Saturn’s moon Enceladus to take images of a geyser vent the size of a small mountain from a distance of about 4,700 kilometers (about 2,900 miles) while whizzing past at a speed of 64,000 kilometers (40,000 miles) per hour. That’s exactly what the Cassini-Huygens mission did last week. In managing this feat, Cassini’s cameras pinpointed the origins of icy jets shooting material out from beneath the surface of this geologically active moon. The image at left shows the target areas and where Cassini spotted those vents.

These geyser-like spouts are in a region of “tiger stripe” terrain, named for the way the surface looks in earlier images of Enceladus. You can see fractures that are about 300 meters (980 feet) deep. The flanks of some of those fractures seem to have deposits of fine material that likely put there as plumes of vapor erupt through the vents. Blocks of ice tens of meters in size and larger (the size of small houses) surround the fractures.

Planetary scientists are really excited about this find because the mission is at last answering a lot of questions about Enceladus and its intriguing surface. “This is the mother lode for us,” said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo. “A place that may ultimately reveal just exactly what kind of environment — habitable or not — we have within this tortured little moon.”

Enceladus has been a puzzle ever since the first Voyager 2 images showed its cracked, strangely repaved surface during a 1981 flyby. That evidence alone told scientists that something was going on with this little ice-covered moon, but they really needed high-resolution images. Voyager 2 was the reconnaissance mission to Cassini’s “in depth” followup.

So, how is Enceladus doing it?  What’s going on with those vents to cause what we see? It’s all in how material gets from relative warm areas deep inside Enceladus to the frigid surface. Imaging scientists suggest that once warm vapor rises from underground to the cold surface through narrow channels, the icy particles may condense and seal off an active vent. Because the material underneath is warmer and under some amount of pressure, it has to erupt somewhere, so eventually new jets probably appear elsewhere along the same fracture in fairly short order.

There’s more to come from the Cassini mission folks. To follow the action, check out new images at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org.  Check it out!