Officially, NASA's mission that went to the moon ended when they flew the Apollo 17 on December 17, 1972. After that the United States decided to terminate the exploration of the moon. Unbeknownst to the public, NASA actually launched one more mission to the moon but the mission ended tragically, and make the government was forced to assume this mission never existed.
Intermittent one year from the launch of Apollo 17, NASA sent two astronauts actually they are using the Apollo 18 flight. Place so the purpose was fixed: the Moon. Unfortunately, unlike previous missions, NASA's mission this time can not be considered a success. There's something that makes this mission ends messy and forced NASA had to cover up the existence of this mission.
Apollo 18's successful landing on the moon. Unfortunately, at that time the astronauts found that they were not the only living creatures on this earth satellites. There are other creatures that are not from the earth and they were totally unfriendly. The fate of these two astronauts and NASA ended tragically forced to assume this mission never happened.(MPA / roc)