Cassini Prepares to Swoop by Saturn's Geyser-Spewing Moon

Aug 07, 2008
Artist concept of Cassini flying by Enceladus. Image credit: NASA/JPL

(PhysOrg.com) -- Fractures, or "tiger stripes," where icy jets erupt on Saturn's moon Enceladus will be the target of a close flyby by the Cassini spacecraft on Monday, Aug. 11.

Cassini will zoom past the tiny moon a mere 50 kilometers (30 miles) from the surface. Just after closest approach, all of the spacecraft's cameras -- covering infrared wavelengths, where temperatures are mapped, as well as visible light and ultraviolet -- will focus on the fissures running along the moon's south pole. That is where the jets of icy water vapor emanate and erupt hundreds of miles into space. Those jets have fascinated scientists since their discovery in 2005.

"Our main goal is to get the most detailed images and remote sensing data ever of the geologically active features on Enceladus," said Paul Helfenstein, a Cassini imaging team associate at Cornell University in Ithaca, NY. "From this data we may learn more about how eruptions, tectonics, and seismic activity alter the moon's surface. We will get an unprecedented high-resolution view of the active area immediately following the closest approach."

Seeing inside one of the fissures in high resolution may provide more information on the terrain and depth of the fissures, as well as the size and composition of the ice grains inside. Refined temperature data could help scientists determine if water, in vapor or liquid form, lies close to the surface and better refine their theories on what powers the jets.

Imaging sequences will capture stereo views of the north polar terrain, and high resolution images of the south polar region will begin shortly after closest approach to Enceladus. The image resolution will be as fine as 7 meters per pixel (23 feet) and will cover known active spots on three of the prominent "tiger stripe" fractures.

In addition to mapping the moon's surface in visible light as well as infrared and ultraviolet light, Cassini will help determine the size of the ice grains and distinguish other elements mixed in with the ice, such as oxygen, hydrogen, or organics.

"Knowing the sizes of the particles, their rates and what else is mixed in these jets can tell us a lot about what's happening inside the little moon," said Amanda Hendrix, Cassini ultraviolet imaging spectrograph team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Other instruments will measure the temperatures along the fractures, which happen to be some of the hottest spots on the moon's surface.

"We'd like to refine our numbers and see which fracture or stripe is hotter than the rest because these results can offer evidence, one way or the other, for the existence of liquid water as the engine that powers the plumes," said Bonnie Buratti of JPL, team member on Cassini's visual and infrared mapping spectrometer.

Cassini discovered evidence for the geyser-like jets on Enceladus in 2005, finding that the continuous eruptions of ice water create a gigantic halo of ice and gas around Enceladus, which helps supply material to Saturn's E-ring. This marks Cassini's second flyby of Enceladus this year. During Cassini's last flyby of Enceladus in March, the spacecraft snatched up precious samples and tasted comet-like organics inside the little moon. Two more Enceladus flybys are coming up in October, and they may bring the spacecraft even closer to the moon. The Oct. 9 encounter is complimentary to the March one, which was optimized for sampling the plume. The Oct. 31 flyby is similar to this August one, and is again optimized for the optical remote sensing instruments.

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User comments : 3

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holoman
1 / 5 (2) Aug 07, 2008
Is it just me or our we missing something.

A few days ago Physorg put out a piece about China having more scientist and making more advances then any other country ???????

I have yet to see a Chinese Cassini, or any other great Chiness space exploration. Heck they aren't even part of ISS.

The only thing great by China (not great !) was blowing up a satellite in LEO causing >10,000 fragments to rain in LEO space causing major problems for the rest of the worlds space experiments,, smart.

So how in the heck can China be so advanced ?

I guess the view is in the eye of the beholder and in this beholder's idea America, Europeans, Japanese, and Koreans are light years ahead of other countries in advanced science.

Pounding on ones chest exclaiming loquaciously we are great doesn't make you great, great deeds do !

NASA and the folks working with NASA truly are
great scientist and great people !!


ShadowRam
5 / 5 (1) Aug 08, 2008
I don't see how bashing China has anything to do with this article?
DoctorKnowledge
not rated yet Aug 08, 2008
ShadowRam: holoman's idea being that the US is making monumental scientific discoveries in space, and China is making none.

There important problems with the observation, though:

1) Cassini is a NASA and ESA project (remember the days when NASA could do it all itself?)

2) Cassini was launched 11 years ago, and it was developed years before that. I.e., It doesn't represent current NASA or ESA prominence, but the stature they had 15 years ago.

3) The Chinese are moving quickly enough in space that there are already people saying they can get to the moon faster than NASA can, now.

4) China has billions in surplus every year. It wouldn't take long for them to catch up, if they wanted to.

Cassini isn't evidence to be smug, vis-a-vis China.

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