Cassini Finds Plethora of Plumes, Hotspots at Enceladus

Feb 23, 2010
In this unique mosaic image combining high-resolution data from the imaging science subsystem and composite infrared spectrometer aboard NASA's Cassini spacecraft, pockets of heat appear along one of the mysterious fractures in the south polar region of Saturn's moon Enceladus. Image credit: NASA/JPL/GSFC/SWRI/SSI

(PhysOrg.com) -- Newly released images from last November's swoop over Saturn's icy moon Enceladus by NASA's Cassini spacecraft reveal a forest of new jets spraying from prominent fractures crossing the south polar region and yield the most detailed temperature map to date of one fracture.

The new images from the imaging science subsystem and the composite infrared spectrometer teams also include the best 3-D image ever obtained of a "tiger stripe," a fissure that sprays icy particles, water vapor and . There are also views of regions not well-mapped previously on , including a southern area with crudely circular tectonic patterns.

"Enceladus continues to astound," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "With each Cassini flyby, we learn more about its extreme activity and what makes this strange moon tick."

For Cassini's visible-light cameras, the Nov. 21, 2009 flyby provided the last look at Enceladus' south polar surface before that region of the moon goes into 15 years of darkness, and includes the most detailed look yet at the jets.

Scientists planned to use this flyby to look for new or smaller jets not visible in previous images. In one mosaic, scientists count more than 30 individual geysers, including more than 20 that had not been seen before. At least one jet spouting prominently in previous images now appears less powerful.

"This last flyby confirms what we suspected," said Carolyn Porco, imaging team lead based at the Space Science Institute in Boulder, Colo. "The vigor of individual jets can vary with time, and many jets, large and small, erupt all along the tiger stripes."

A new map that combines heat data with visible-light images shows a 40-kilometer (25-mile) segment of the longest tiger stripe, known as Baghdad Sulcus. The map illustrates the correlation, at the highest resolution yet seen, between the geologically youthful surface fractures and the anomalously warm temperatures that have been recorded in the south polar region. The broad swaths of heat previously detected by the infrared spectrometer appear to be confined to a narrow, intense region no more than a kilometer (half a mile) wide along the fracture.

In these measurements, peak temperatures along Baghdad Sulcus exceed 180 Kelvin (minus 135 degrees Fahrenheit), and may be higher than 200 Kelvin (minus 100 degrees Fahrenheit). These warm temperatures probably result from heating of the fracture flanks by the warm, upwelling water vapor that propels the ice-particle jets seen by Cassini's cameras. Cassini scientists will be testing this idea by investigating how well the hot spots correspond with the jet sources.

"The fractures are chilly by Earth standards, but they're a cozy oasis compared to the numbing 50 Kelvin (-370 Fahrenheit) of their surroundings," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute in Boulder, Colo. "The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground. Results like this make Enceladus one of the most exciting places we've found in the solar system."

Some of Cassini's scientists infer that the warmer the temperatures are at the surface, the greater the likelihood that jets erupt from liquid. "And if true, this makes Enceladus' organic-rich, liquid sub-surface environment the most accessible extraterrestrial watery zone known in the solar system," Porco said.

The Nov. 21 flyby was the eighth targeted encounter with Enceladus. It took the spacecraft to within about 1,600 kilometers (1,000 miles) of the moon's surface, at around 82 degrees south latitude.

Explore further: Amazing raw Cassini images from this week

More information: The images and additional information are online at www.nasa.gov/cassini .

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omatumr
2 / 5 (2) Feb 23, 2010
Fission is probably the heat source.

Fission is probably also the source of anomalous heat in Jupiter.

Light elements like H, He, C and N are abundant in the outer planets and their satellites. Rapid neutron capture made actinide elements (Th, U, Pu, etc) in the outer region of the supernova that gave birth to the solar system. That is where H, He, C and N were abundant.

Excess Xe-136 from rapid neutron capture have been observed in carbon-rich inclusions of meteorites and in the He-rich atmosphere of Jupiter.

With kind regards,
Oliver K. Manuel
yyz
1 / 5 (1) Feb 24, 2010
Dr. Manuel,

Are you proposing a low density ice moon with a radius of 252km is capable of sustaining nuclear fusion. Knowing your professional background, are you really serious? Is this 'knowledge' what you taught your students? I feel sorry for them.
Adriab
5 / 5 (1) Feb 24, 2010
So two of the major contributors to heating on a body this far out in the solar system would be tidal forces from Saturn (and to a much lesser extent the other gas giants), and radioactive decay inside the moon.

What I am wondering is, could the interaction of Enceladus with Saturn's magnetosphere have a significant impact on heating of the moon?

My guess is, yes there is an interaction, but the effects are nearly negligible.
Husky
1 / 5 (1) Feb 24, 2010
What oliver says doesn't sound as crazy as it would first appear, Common sense and gravity has that metallic planets and heavier elements tend to aggregate near the center of starsystems, but if also heavy elements were formed on the outer edge of an supernova or found itselve on the very edges of a new protoplanety disk, they would likely be captured by gasgiants before they could fall all the way to the central ragions. An watery/icy envelope would act as a perfect capture for thermal neutrons and thus rapid heating, but the ice crust prevents direct neutron emission detection, however this exotic theory could be possibly be verivied if cassini wqould detect a substantial amount of heavy water isoptopes in the plumes contents.
yyz
1 / 5 (1) Feb 24, 2010
"What oliver[sic] says doesn't sound as crazy as it would first appear".

Of course all other ice bodies larger than Enceladus would likely be fusion-powered too, following this 'logic'. I guess this would be a variant of cold fusion (LENR).
barakn
4 / 5 (1) Feb 25, 2010
Yyz, you misread omatumor's post. It said fission, not fusion.
yyz
4 / 5 (1) Feb 25, 2010
My apologies. But as I see it you still have a problem sustaining a fission reaction on a ball of ice 252km in radius. How do you propose this feat, exactly. And why aren't other ice moons surrounding the gas giants also undergoing a fission reaction. Surely Enceladus is not the only example of this fissioning scenario. Occams razor.
barakn
not rated yet Feb 25, 2010
I don't believe he mentioned neutron-induced fission either (despite his hang-ups about neutrons). I believe he was thinking of the spontaneous fission of natural radionuclides. He can't, of course, explain how a mostly-water moon would have enough radioactive material to warm it or how such a small object (thus with a large surface-area to volume ratio) would retain that heat.