NASA's Gravity Recovery And Interior Laboratory (GRAIL) mission came to an end on Monday as planned when its two spacecraft de-orbited and crashed into the surface of the moon.<br/> <br />The first of the orbiters, Ebb, hit a predetermined mountain near the lunar north pole, with its twin, Flow, hitting nearby 30 seconds later.<br/> <br />Both were travelling at a speed of 1.7 kilometres per second.<br/> <br />The two craft were launched in September of 2011.<br/> <br />Following a successful mission mapping the gravity of the moon, the washing machine-sized spacecraft were nearly out of fuel.<br/> <br />(SOUNDBITE) (English) GRAIL PRINCIPAL INVESTIGATOR DR. MARIA ZUBER, SAYING:<br/> <br />"Ebb and Flow have removed a veil from the moon and removing this veil will enable discoveries about the way the moon formed and evolved for many years to come."<br/> <br />The GRAIL primary mission yielded the highest-resolution gravity field map of any celestial body to date.<br/> <br />The map will provide a better understanding of how the moon, Earth and other terrestrial planets in the solar system formed and evolved.
