Twin NASA probes plunge into lunar mountain on purpose (4)

（Xinhua）  14:41, December 18, 2012

Since then, the duo spent almost a year mapping the moon's gravity in unprecedented detail. The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

"We will miss our lunar twins, but the scientists tell me it will take years to analyze all the great data they got, and that is why we came to the moon in the first place," said GRAIL project manager David Lehman. "So long, Ebb and Flow, and we thank you."

More than 100 missions have been flung to Earth's nearest neighbor since the dawn of the Space Age. Included were NASA's six Apollo moon landings that put 12 astronauts on the surface.

The demise of Ebb and Flow comes in the same month as the 40th launch anniversary of Apollo 17, the last manned mission to the moon. The last time NASA intentionally fired manmade objects at the moon was in 2009.