US President Richard Nixon had a speech ready to go in the event that Apollo 11 ended in disaster.
A mission to Mars could come as early as 2033, Bridenstine told reporters on Monday.
This model took a team of master LEGO builder nearly 300 hours to make, using more than 30,000 plastic bricks.
To celebrate the anniversary, NASA has restored the old control room from which the Apollo-era flight directors oversaw the mission. It's a place of pilgrimage for their successors.
As the 50th anniversary of the groundbreaking Apollo 11 mission nears, the question that has excited conspiracy theorists for half a century is still there: did humans actually set foot on the moon?
As commemoration mark 50 years since man first stepped on the moon, Europe's space chief has been talking about his plans for Earth's natural satellite.
"If Neil Armstrong wasn't a hero, then there are no heroes," said US Vice President Mike Pence.
Stargazers in Europe, Africa, Latin America and Asia were treated to a partial lunar eclipse in the night between Tuesday and Wednesday, just as the world was commemorating the launch of the Apollo 11 mission in 1969.
Buzz Aldrin, second man on moon, recalls 'magnificent desolation'
Astronaut Michael Collins returned to the Apollo 11 launch pad on the 50th anniversary of the mission to land on the moon.