Nasa has successfully crashed two spacecraft into the Moon - on purpose.
The two craft ('Ebb' and 'Flow') which together made up the Gravity Recovery and Interior Laboratory (Grail) mission, were intentionally targeted at the Moon after completing their operations.
The washing machine-sized craft were sent to the Moon to help map the fine details in the Moon's gravity and understand more about what it's made of and how it was formed.
They slammed into the side of a 2km-high mountain at about 10.30 pm UK time, located about 3km apart.
Ebb and Flow were placed in orbit around the Moon in March, and have since produced the most detailed gravity map of any body in the Solar System - including Earth.
"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," said principal investigator Prof Maria Zuber from the Massachusetts Institute of Technology, according to the BBC.
Preliminary results from the mission were released earlier this month, and were already being described as far-reaching and surprising.
Above: Nasa's new gravity map of the Moon
They indicated that the crust of the Moon are much thicker than previously thought. And the conclusions from that are surprisingly far-reaching - it suggests the violent early history of the Solar System led to most rocky planets having deep fractures in their surface.
That in turn means life that may have once existed on Mars might still be there - in an ocean which drained into deep fractures on its surface.