Like sprinklers hidden beneath the surface, a series of geysers — more than previously thought — are gushing water ice from fissures near the south pole of Saturn's icy moon Enceladus, new images reveal.
The newly released images from NASA's Cassini spacecraft show the geysers of Enceladus in stunning detail. The photos caught a bounty of previously unknown plumes alongside known ones, and show at least one gusher that's lost power since NASA's last look at the moon.
The new images were taken during Cassini's flyby on Nov. 21, 2009, and include the best 3-D look ever obtained of a "tiger stripe" — a fissure that sprays icy particles, water vapor and organic compounds. They also show regions of Enceladus that were not well-mapped in previous flybys, including a southern area with crudely circular tectonic patterns.
Both large and small plumes were seen spouting from these famed tigers stripes along Enceladus' south pole. In one mosaic, created by two high-resolution images captured by the narrow-angle camera, 30 individual jets can be seen. More than 20 of them had not been identified before.
By photographing the jets over time, Cassini scientists can study the consistency of their activity.
"This last flyby confirms what we suspected," said Carolyn Porco, Cassini's imaging team lead 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."
The scientists also combined the visible-light images with heat data to create a map of a 25-mile (40-km) segment of the longest stripe, known as Baghdad Sulcus. The map illustrates the link between the geologically youthful surface fractures and the anomalously warm temperatures that have been recorded in the south polar region.
In these measurements, peak temperatures along Baghdad Sulcus exceed minus 135 degrees Fahrenheit (minus 93 degrees Celsius), and may be higher than minus 100 degrees F (minus 73 degrees C).
The temperatures, considered warm for Enceladus, probably result from heating of the fracture flanks by the warm, upwelling water vapor that propels the moon's ice-particle jets.
"The fractures are chilly by Earth standards, but they're a cozy oasis compared to the numbing 50 Kelvin (minus 370 Fahrenheit) of their surroundings," said John Spencer, a composite infrared spectrometer team member based at Southwest Research Institute also in Boulder. "The huge amount of heat pouring out of the tiger stripe fractures may be enough to melt the ice underground."
Some Cassini scientists infer that the warmer the temperatures are at the surface, the greater the likelihood that jets erupt from liquid.
The Nov. 21 flyby, which brought the spacecraft to within 1,000 miles (1,600 km) of the moon's surface, was the eighth targeted encounter with Enceladus. It's the last look at Enceladus' south polar surface before that region goes into 15 years of darkness, NASA officials said.
And now that the Cassini mission has been extended through 2017, with 11 Enceladus flybys slated for the extension period, there are plenty of chances to capture more images of this icy moon. The spacecraft launched in 1997 and has been orbiting Saturn since 2004.
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