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.
The first of the orbiters, Ebb, hit a predetermined mountain near the lunar north pole, with its twin, Flow, hitting nearby 30 seconds later.
Both were travelling at a speed of 1.7 kilometres per second.
The two craft were launched in September of 2011.
Following a successful mission mapping the gravity of the moon, the washing machine-sized spacecraft were nearly out of fuel.
(SOUNDBITE) (English) GRAIL PRINCIPAL INVESTIGATOR DR. MARIA ZUBER, SAYING:
"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."
The GRAIL primary mission yielded the highest-resolution gravity field map of any celestial body to date.
The map will provide a better understanding of how the moon, Earth and other terrestrial planets in the solar system formed and evolved.
