Author: Fraser Cain

Yesterday I blogged about how particles jetting from Enceladus find their way to Saturn’s A-Ring. Now there’s a new report that models how ice and vapour come pouring out of cracks on Enceladus’ surface in the first place.

Since Cassini first discovered jets of water ice blasting out of Saturn’s moon Enceladus, scientists have been trying to explain the process that could make this happen. The moon is very very cold; too far away to be warmed by the Sun.

Scientists now know that the jets are emanating from a series of cracks near Enceladus’ southern pole; these cracks have been dubbed “tiger stripes”. A team of German researchers, led by Juergen Schmidt of the University of Potsdam, have developed a computer model that describes what the bottom of those tiger stripes might look like.

According to Schmidt, they have to be at a temperature of 0 degrees Celsius. This is the triple point of water, where vapour, ice and liquid can all exist at the same time.

Water vapour and ice grains are blasted through funnels in the tiger stripes. The heavier grains rub against the sides of the holes and slow down.

This helps explain why ice particles coming out of Enceladus move at a slower velocity than the water vapour.

The process of tidal heating is probably keeping the interior of Enceladus warm. As it orbits around Saturn, the powerful gravitational force causes the tiny moon to flex back and forth. This creates heat within it. A more dramatic version of this process can be seen with Jupiter’s moon Io, which is heated to the point that volcanoes erupt across its surface.

The surface of Enceladus is -193 degrees Celsius, while the tiger stripes are -133 C. This means that the interior of the moon must be even warmer.

The researchers have published their work in this week’s issue of the journal Nature.

Original Source: Nature

One of the biggest discoveries made by Cassini is at Saturn’s moon Enceladus, where great plumes of icy material were seen spewing from its southern pole. Now scientists think that this material is traveling all the way inward to get trapped into Saturn’s A-ring.

Scientists had already linked together Saturn’s E-ring with the material spewed out by Enceladus. And researchers had worked out that the whole magnetic environment around Saturn is weighed down by the Enceladus material, which becomes plasma.

But now this.

“Saturn’s A-ring and Enceladus are separated by 100,000 kilometers (62,000 miles), yet there’s a physical connection between the two,” says Dr. William Farrell of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Prior to Cassini, it was believed that the two bodies were separate and distinct entities, but Cassini’s unique observations indicate that Enceladus is actually delivering a portion of its mass directly to the outer edge of the A-ring.” Farrell is lead author of a paper on this Saturn discovery that appeared in Geophysical Research Letters January 23.

The gas particles are ejected from Enceladus and then become electrically charged by sunlight and through interactions with other particles. Once they’re charged, the particles can come under the sway of Saturn’s magnetic field, which traps and directs them around. The particles can move around from pole to pole, but once they enter Saturn’s A-ring, they’re stuck there for good.

Scientists had actually predicted this in the early 1990s. Using the Hubble Space Telescope, they saw a large presence of water-related molecules in orbit around Saturn. The researchers modeled the motions of this icy material, and calculated that it could migrate all the way in to the A-ring. But the source of this water cloud was unknown.

This discovery backs up the prediction, and provides a source for the cloud of water-related molecules feeding into the A-ring.

They’re coming from Enceladus.

Original Source: NASA News Release