Nearly 50 years have passed since NASA's Apollo 8 mission orbited the Moon for the first time in history.
On December 21, 1968, astronauts Frank Borman, William Anders, and James Lovell left the Kennedy Space Center to fly around the moon. They spent 20 hours orbiting the lunar orbit and returned home in space after more than six days.
The Apollo 8 mission was a crucial step in achieving President John F. Kennedy's goal of landing a man on the moon.
Nine other lunar missions followed Apollo 8, bringing a dozen men to the moon and collecting hundreds of pounds of rock and soil samples for analysis.
Since then, no American spacecraft has landed on the lunar surface for nearly five decades.
That may change in the next few years. In November, NASA announced that it is offering up to $ 2.6 billion worth of contracts to nine American companies that could land on the moon by 2022. Instead, the space agency wants the private sector to face up to these challenges and provide the opportunity to bring NASA's experiments to the moon.
In the meantime, take a look back at all NASA Apollo missions that flew between 1