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."
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