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NASA to Crash Probes into the Moon

This still image and animation shows the final flight path for NASA's twin Gravity Recovery and Interior Laboratory (GRAIL) mission spacecraft, which will impact the moon on Dec. 17, 2012.
NASA is going to crash two lunar probes into the moon this Monday.

The U.S. space agency's twin spacecraft, named Ebb and Flow, will fly low over the moon's surface and crash into the rim of a crater, the final move of a successful lunar-mapping mission.
Intentional impacts
These controlled crashes have been part of the plan from the mission's outset, but there will not be any live visuals, because the impacts are going to happen in the dark.

The mission's principal investigator, Maria Zuber of the Massachusetts Institute of Technology, says people should not expect a dramatic, fiery end for the Gravity Recovery and Interior Laboratory, or GRAIL, mission spacecraft.

"We are not expecting a big flash or a big explosion, okay? These are two small spacecraft," Zuber told reporters during a NASA news conference Thursday. "They are, I will use the term 'apartment-sized washer and dryer-sized' spacecraft with empty fuel tanks, so we're not expecting a flash that is visible from Earth."

Crash data
Zuber says researchers will rely on the Lunar Reconnaissance Orbiter spacecraft, which has very sensitive instruments, to provide data about the crashes. That orbiter has sent images of the planned impact site and will do so again after the crash so that scientists can try to identify the impact points.
Ebb and Flow will be traveling about 1.7 kilometers per second when they crash into the lunar surface, about 20 seconds apart. Mission managers say they do not expect the crashes to disturb any historic lunar landing sites.
Successful mission
GRAIL's twin probes began orbiting the moon one year ago. Zuber says they have significantly contributed to science by providing valuable information about the moon's structure and composition. The mission also provided a high-resolution gravity field map of the moon.
"We now will be able to navigate extremely precisely to the moon in ways such that if there is a particular place that a future robotic or human mission wanted to land, you would be able to do that extremely precisely, which will facilitate future exploration," said Zuber.
Ebb and Flow will not be the first craft to crash into the moon. NASA's GRAIL mission web page says 12 U.S., Soviet and Japanese spacecraft crashed into the moon's surface between 1959 and 1993.