Cassini Finds “Heat” and More Geysers on Enceladus


Newly released images from last November’s close flyby over Saturn’s icy moon Enceladus the Cassini spacecraft reveal geyser jets spraying all along the prominent fractures, or “tiger stripes” that cross the moon’s south polar region. Additionally, a new detailed temperature map of one fracture reveals warmer temperatures than what was expected. “Enceladus continues to astound,” said Bob Pappalardo, Cassini project scientist at the Jet Propulsion Laboratory. “With each Cassini flyby, we learn more about its extreme activity and what makes this strange moon tick.”

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

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

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 ( – 92 C, -135 F), and may be higher than 200 Kelvin (- 73 C, -100 F). 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 (-223 C, -370 F) 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.

Source: JPL

14 Replies to “Cassini Finds “Heat” and More Geysers on Enceladus”

  1. Only Belize, Burma, The United States and Liberia still use Fahrenheit.

    Celsius makes alot more sense to the rest of us, but we’ll settle with kelvin :p

  2. Oh wow!

    30 openings – I know that we can look at the integrated result (the E ring, I believe), but it’s anyway thought provoking to go from a handful of sulci to a major, and at least for now robust, process.

    Likewise, someone claimed elsewhere that 180 K places ammonia-water mixtures as at least partially liquid. That makes liquid jets/liquid source a consistent with prediction hypothesis.

    This _must_ be good science, because it raises more questions than it answers.

  3. Most of us in Britain still use Fahrenheit! As an astronomer though I do use the Kelvin scale.

  4. I bet that if you asked people on the street ‘most’ would use celsius, unless you mean within astronomy circles, i that case i dont know 🙂

  5. Clearly there is an energy flow through with respect to Enceladus, where I always thought this sounded like something on a Mexican resturant menu. Presumably due to orbital energy (spin-orbit coupling), which is generating the heat source for this activity. Are there any references on this, such as the magnitude of this energy flow?


  6. Paul Eaton-Jones:

    Most of us in Britain still use Fahrenheit!

    What are you talking about, man? The BBC have been giving weather reports in Celsius since Britain joined the European Union in the early 1970s (then known as the Common Market).

  7. @ Aqua,

    No, that is not possible. Orbital maneuvers require what is called a Delta v, change in velocity, which is related to energy, Delta v = sqrt{2E/m}. That energy involves fuel, which Cassini does not have that much of. Its primary engine was used to put in orbit around Saturn, and for small orbital changes in that system. To get into orbit around one of the moons would require lots of fuel, more than available.


  8. I wonder if it will be possible in the next couple of decades to send an orbiter with a scoop to grab some of the ice being shot out, and an on-board analyzer to scan for chemical makeup and possibly life?

    Would be far easier than any other moon, where you have to drill through possibly miles of life before you can analyze anything.

  9. I was thinking about tweaking the orbital dynamic enough by making a couple close aerobraking passes at Titan first?
    Or arranging a series of close encounters with several of the moons?

  10. Again that is very unlikely to work. Cassini was not desgned for this. It is not hard to see the problems. Such aerobraking would place torques on the craft and screw up its axis stabilization, it would impose shock heating on its main antenna and RTG and boom assembly and so forth. Chances are almost certain that if this were attempted that would be the last we would hear from Cassini.


  11. Please use all three temperature scales. I was very pleased at the way tall three were noted in this article.

  12. BTW-

    The original NASA JPL new release used Kelvin (and F in parenthesis). So, Nancy did add the C measurements for us.

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