Cassini Images Reveal Spectacular Evidence Of An Active Moon

Space Daily.com ^ | Dec 07, 2005 | JPL, NASA

[tricky_k_1972]

Cassini Images Reveal Spectacular Evidence Of An Active Moon

Recent Cassini images of Saturn's moon Enceladus backlit by the sun show the fountain-like sources of the fine spray of material that towers over the south polar region. Image credit: NASA/JPL/Space Science Institute.

Pasadena CA (JPL) Dec 07, 2005

Jets of fine, icy particles streaming from Saturn's moon Enceladus were captured in recent images from NASA's Cassini spacecraft. The images provide unambiguous visual evidence that the moon is geologically active.

"For planetary explorers like us, there is little that can compare to the sighting of activity on another solar system body," said Dr. Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, Colo.

"This has been a heart-stopper, and surely one of our most thrilling results."

The Cassini images clearly show multiple jets emanating from the moon's south polar region. Based on earlier data, scientists strongly suspected these jets arise from warm fractures in the region. The fractures, informally dubbed "tiger stripes," are viewed essentially broadside in the new images.

The fainter, extended plume stretches at least 186 kilometers (300 miles) above the surface of Enceladus, which is only 186 kilometers wide. Cassini flew through the plume in July, when it passed a few hundred kilometers above the moon.

During that flyby, Cassini's instruments measured the plume's constituent water vapor and icy particles.

Imaging team members analyzed images of Enceladus taken earlier this year at similar viewing angles. It was a rigorous effort to demonstrate that earlier apparitions of the plumes, seen as far back as January, were in fact real and not due to imperfections in the camera.

The recent images were part of a sequence planned to confirm the presence of the plumes and examine them in finer detail. Imaging team member Dr. Andrew Ingersoll from the California Institute of Technology, said, "I think what we're seeing are ice particles in jets of water vapor that emanate from pressurized vents. To form the particles and carry them aloft, the vapor must have a certain density, and that implies surprisingly warm temperatures for a cold body like Enceladus."

Imaging scientists are comparing the new views to earlier Cassini data in hopes of arriving at a more detailed, three-dimensional picture of the plumes and understanding how activity has come about on such a small moon. They are not sure about the precise cause of the moon's unexpected geologic vitality.

False-color views of Saturn's cratered, icy moons, Rhea and Dione. Image credit: NASA/JPL/Space Science Institute.

"In some ways, Enceladus resembles a huge comet," said Dr. Torrence Johnson, imaging team member from NASA's Jet Propulsion Laboratory.

"Only, in the case of Enceladus, the energy source for the geyser-like activity is believed to be due to internal heating by perhaps radioactivity and tides rather than the sunlight which causes cometary jets." The new data also give yet another indication of how Enceladus keeps supplying material to Saturn's gossamer E ring.

Cassini's Photo Album From A Season Of Icy Moons
Pasadena CA (JPL) Dec 07 - Wrapping-up a phenomenally successful year of observing Saturn's icy moons, the Cassini mission is releasing a flood of new views of the moons Enceladus, Dione, Rhea, Hyperion, and Iapetus.

The moons and their intricacies are being highlighted today at a news briefing held today at the American Geophysical Union meeting in San Francisco, Calif.

Several new images of Rhea, a moon measuring 1,528 kilometers (949 miles) across, were taken during Cassini's most recent close flyby on November 26. During the encounter, Cassini dipped to within 500 kilometers (310 miles) of Rhea's surface.

Additional new images include two "zoomable" mosaics of Rhea and Hyperion at high resolution; false-color views revealing compositional variation on the surfaces of Hyperion, Dione and Rhea; two movies reproducing Cassini's exciting encounters with Iapetus and Hyperion; and dazzling new images of the plumes of Enceladus, including a time-lapse movie.

[staytrue]

I think the Moon, is important because the Moon-formation collision that is now the leading candidate for how it formed reliquified the Earth and likely contributed heavy elements, iron, and water to the young Earth. This has kept our core molten

I think the moon is important too and the moon/earth system is a billion to one chance against. Further, you are right about keeping the core liquid but maybe not for the right reason. The moon has no iron core. Most likely the iron core of the incoming object merged with earth while the lighter stuff got blasted into orbit to form the moon. This left earth with a bigger than normal core than mars or venus and this made it slower to crystallize.

[TN4Liberty]

They aren't allowed to talk, of course.

Yeah, that makes for great radio.

[Question_Assumptions]

I think the moon is important too and the moon/earth system is a billion to one chance against.

It could be higher than that. Robin Canup and others have done simulations of the sort of collision needed to create our moon and it's a fairly specific range of speeds and angles. Even when that's correct, about a third of their simulations produced an unstable two moon system that broke down after about a century.

Further, you are right about keeping the core liquid but maybe not for the right reason. The moon has no iron core. Most likely the iron core of the incoming object merged with earth while the lighter stuff got blasted into orbit to form the moon. This left earth with a bigger than normal core than mars or venus and this made it slower to crystallize.

That's actually a large part of what I had in mind. I think the collision did add heat but I think the bigger contribution was, as you point out, the addition of iron and heavy (possibly radioactive) elements to the Earth's core that are necessary to drive the magnetic field. Of course it's also possible that the off-center collision that Canup and others speciulate about set the whole thing spinning faster, too. If the poles are about to reverse (or the magnetic field is about to disappear, as some real alarmists speculate), we'll get a good lesson in just how important our magnetic field is to life on Earth the hard way.

[staytrue]

Past Magnetic field reversal does not appear to have bad effects on life. I suspect that most animals adapted by taking a siesta from 10 am to 2 pm and underwater animals had no problem.

[RightWhale]

A couple proponents of the artificial moon idea were on Coast last night. For some reason which I do not know, Hoagland showed up to hog their time, but they did make their point, which is that the chances of such an extreme moon are so small that the superior and more likely idea is that the moon was built by time travellers from our near future about 600 million years ago to make earth habitable.

[Question_Assumptions]

I think you should post that on the thread discussing the similarities between Intellgent Design and SETI. :-)

[Question_Assumptions]

I think you should post that on the thread discussing the similarities between Intell[i]gent Design and SETI. :-) Ooops. The tread title is "SETI and Intelligent Design"

[lexington minuteman 1775]

And a taco to go.

[bert]

....Looks like a hole in the Ozone layer...dang those SUV's....

And my wife says.."why do you spend so much tome on Free Republic"

I would have to live without this outstanding observation by Deguello. The atmosphere must definitely have a discontinuity where the matter is being ejected.

[BikerNYC]

Astronipple?

[bert]

.....Their might be some other limiting factor ......

They came as insects and live among us as termites.

[Tolkien]

You beat me to it.

[SunkenCiv]

Note: this topic is from 12/07/2005. Thanks tricky_k_1972.

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