This three-image mosaic is the highest resolution view yet obtained of Enceladus' north polar region. The view looks southward over cratered plains from high above the north pole of Enceladus. NASA's Cassini probe caught this view during a March 12, 2008 flyby.
Credit: NASA/JPL/Space Science Institute
This story was updated at 5:40 p.m. EDT.
The Cassini spacecraft has beamed home the most detailed views yet of Saturn?s moon Enceladus despite a software glitch that prevented a key instrument from sampling the satellite?s geyser-like ice plumes during a flyby.
Cassini whipped by Enceladus on Wednesday at a clip of about 32,000 mph (51,499 kph) during the first of several swings past the icy moon of its extended mission. Scientists on Earth were hoping not only to photograph the moon, but also determine the composition of its water-ice geysers using a particle analyzing spectrometer and other instruments.
But one tool, known as the Cosmic Dust Analyzer and Ion and Neutral Mass Spectrometer, hung up while switching between two versions of software and did not record data as Cassini flew through the plumes.
?Right now, we don?t know exactly what happened,? the instrument?s principal investigator Ralf Srama, of the Max Planck Institute of Astrophysics in Heidelberg, Germany, told SPACE.com. ?We think it was some kind of timing issue.?
Whatever the cause, the glitch popped up at just the wrong time - as Cassini passed 120 miles (193 km) above Enceladus? southern polar region and skirted through the edges of water-ice plumes gushing from cracks in the moon?s surface. The instrument was unable to record any data for several hours during the pass, but has since recovered completely, Srama said.
While the specific cause of the hiccup is unknown, engineers have isolated it to the in-flight software switch, which worked perfectly during a series of tests on Earth.
?We are disappointed about this, but we were able to pin down the problem,? said Srama. ?This means we will not repeat this problem.?
Cassini?s Wednesday flyby past Enceladus is the first of four close-up swings past the moon this year, with a similar plume pass slated for Oct. 9, NASA officials said.
A whole new view
Cameras aboard Cassini recorded the probe?s approach and departure at Enceladus during the flyby, which skimmed just 30 miles (50 km) above the moon?s surface at the nearest point.
The new views shed light on Enceladus? north pole, which appeared peppered with craters and seems much older than the moon?s southern polar region, mission managers said.
"These new images are showing us in great detail how the moon's north pole differs from the south, an important comparison for working out the moon's obviously complex geological history," said Carolyn Porco, Cassini imaging team leader and the Space Science Institute in Boulder, Colo., in a statement late Thursday. "And the success of yesterday's daring and very low-altitude flyby means this coming summer's very close encounter, when we get exquisitely detailed images of the surface sources of Enceladus' south polar jets, should be an exciting 'next big step' in understanding just how the jets are powered."
Although Cassini?s cosmic dust-analyzing spectrometer failed to observe the composition and size of Enceladus? plume material, four other instruments functioned perfectly, mission managers said.
Cassini first spotted the plumes of Enceladus in 2005. The icy material spewing out of the moon?s southern fissures may point to an ocean just beneath the surface and provide the raw material that makes up Saturn?s wispy E-ring, mission managers said.
?It was very exciting,? Srama said of the flyby, adding that he is looking ahead to Cassini?s next close swing past the icy moon. ?Enceladus was really an outstanding target ? our contribution to understanding it will have to wait until the next time.?
- VIDEO: Enceladus, Cold Faithful
- IMAGES: Cassini's Latest Discoveries
- Special Report: Cassini's Mission to Saturn