Artist's impression of Grail twins
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Nasa gravity satellites slam into Moon

18 December 2012 Last updated at 06:54 GMT

Two Nasa satellites monitoring the Moon have been deliberately crashed onto the surface.

The spacecraft - named Ebb and Flow - had spent a year orbiting the moon, measuring its gravity field to learn more about the interior.

Running low on fuel, Nasa engineers decided to crash the spacecraft into a mountain. James Kelly reports.