This story was updated at 12:51 p.m. EDT.
A NASA spacecraft and its trusty
rocket stage are drawing ever closer to the moon to intentionally crash to
their doom Friday, all in the name of science.
The cosmic collisions are expected
to kick up tons of moon dirt in giant
debris plumes that will then be scanned for signs of water ice suspected to
be buried beneath the floor of a permanently shadowed crater at the lunar south pole.
"Everybody is feeling very excited,"
said Victoria Friedensen, NASA's program executive
for the LCROSS mission at the heart of the moon crash. "There is a great sense
of anticipation."
Moon crash
NASA launched the
LCROSS probe in June along with a powerful lunar orbiter that is currently
circling the moon to determine whether water ice, which could be a vital
resource for astronauts in the future, actually exists in the perpetual darkness
of craters at the moon's south pole.
Since then, the $79 million LCROSS —
short for Lunar Crater Observation Sensing Satellite — has made three long
loops around the Earth while attached to an empty Centaur rocket stage, its
first weapon in the upcoming lunar double whammy.
The two vehicles are due to separate
late tonight and the first impact is set for 7:31 a.m. EDT (1131 GMT). That's
when the 42-foot (13-meter) long Centaur rocket stage will plow into the crater
Cabeus at the moon's south pole.
NASA will start broadcasting the event live on NASA TV at
6:30 a.m. EDT (1030 GMT).
Seasoned amateur astronomers may be
able to see the crash using 10 or 12-inch telescopes depending on their
location, local weather and lighting conditions. [Click
here to see how to watch the LCROSS moon crashes.]
The Centaur rocket stage weighs
5,216 pounds (2,366 kg), about as much as a sport utility vehicle, and will
slam into the moon at about 5,600 mph (9,010 kph).
Researchers believe the blast will create a debris plume about 12 miles (20 km)
wide and send moon dirt soaring to heights of 6.2 miles (10 km), where it would
be illuminated by the sun.
"It will kick up whatever is on the
floor of the crater," LCROSS project manager Daniel Andrews has said. "That may
very well include water ice."
But the first crash is only the
prelude. Riding aboard the LCROSS spacecraft are nine different science
instruments, including cameras that will beam live views of the impact back to
NASA's mission operations center at the Ames Research Center in Moffett Field,
Calif. Those tools will be used to scan the debris plume for evidence of water ice.
"We expect to see the crater getting
closer and closer," Friedensen told SPACE.com.
The 1,664-pound (891-kg) LCROSS
shepherding craft will follow its Centaur rocket stage down to make its own
crash about four minutes after the initial lunar hit.
More than 20 observatories on Earth,
as well as a host of amateur astronomers, museums and volunteers will
be watching the two crashes to search for signs of any water ice in the
debris clouds. The Hubble Space Telescope and other space-based observatories
will also turn their camera eyes on the moon for the event.
"Our last day in flight promises to
be the most challenging and the most rewarding for the project," LCROSS flight
director Paul Tomkins wrote in his NASA blog today. "Our 112 days in orbit
are focused entirely on the last four minutes, after the Centaur impacts our
target crater and raises a plume of lunar material for the LCROSS Shepherding
Spacecraft to observe for signs of water, but before the Shepherd also impacts
the moon."
Unlike other spacecraft that have
smacked the moon, like Japan's recent Kaguya probe,
Europe's Smart-1 and NASA's Lunar Prospector, the LCROSS impactors
will hit at a steep angle in order to get the biggest boom for their buck,
mission managers said.
LCROSS has not had a completely
smooth ride to the moon. An August glitch forced the spacecraft to use much of
its propellant supply, but not enough to prevent its ultimate mission.
NASA also unexpectedly switched
target craters last week, choosing the 60-mile (98-km) wide Cabeus
over its nearby neighbor Cabeus A because data
suggested the new target had a higher concentration of hydrogen — a signal for
potential water ice.
Hunting moon water
Scientists already know that some small
amount of water exists on the moon, but LCROSS is designed to seek out
buried water ice at the lunar south pole — a region where the sun has never
shined on some craters with permanent shadows.
NASA scientists say the areas may be
the coldest places in the solar system, with temperatures reaching minus 400
degrees Fahrenheit (minus 240 Celsius) in the crater shadows. Finding usable
amounts of water ice would be a boon for NASA's vision to send astronauts back
to the moon by the mid-2020s.
But Friedensen
said that it will take time before scientists know if any water is present in
the debris plumes. A few hours after the two impacts, LCROSS scientists will
hold a press conference, but will likely only be able to discuss how accurate
the hits were, she added.
"We will not be able to talk about how
much water is there, if it's water we find," she said. "The science team
will need a couple of days, maybe even a couple of weeks to make sure."
The live stream of data from LCROSS
will be recorded in triplicate — at the mission control center at Ames and two
other sites — to make sure it is saved for posterity, Friedensen
added.
Tompkins said that knowing LCROSS
will soon meet its fate is a bit sad, even if it was already preordained for
the cause of science.
"Well, we all knew it was going to
happen. It was inevitable. It was the whole design of the mission,"
he wrote. "LCROSS was destined to end its wonderfully fantastic journey by
intentionally crashing into a permanently shadowed crater at the south pole of
the moon."
SPACE.com is providing full coverage of the LCROSS moon crash. Click
here for a look at the mission and return to SPACE.com at 6:30 a.m. ET
(1030 GMT) for live crash coverage.
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