Moon by the Soviet Union's Luna 2, an unmanned spacecraft. The United States' NASA Apollo program achieved the only manned lunar missions to date, beginning with the first manned orbital mission by Apollo 8 in 1968, and six manned landings between 1969 and 1972, with the first being Apollo 11. These missions returned lunar rocks which have been used to develop a geological understanding of the Moon's origin, internal structure, and the Moon's later history. Since the Apollo 17 mission in 1972, the Moon has been visited only by unmanned spacecraft. Both the Moon's natural prominence in the earthly sky and
Exploration of the Moon and avoid a space race Germany also announced in March 2007 that it would launch a national lunar orbiter, LEO in 2012. However the mission was cancelled due to budgetary constraints. In August 2007, NASA stated that all future missions and explorations of the Moon will be done entirely using the metric system. This was done to improve cooperation with space agencies of other countries which already use the metric system. The European Space Agency has also announced its intention to send a manned mission to the Moon, as part of the Aurora programme. In September 2010, the agency introduced