Buzz Aldrin, Mike Collins & Neil Armstrong President Obama

This week marked the 40th anniversary of the Apollo 11 moon landing, the first time humans set foot on another celestial body. The Apollo 11 astronauts, from left, Buzz Aldrin, Michael Collins and Neil Armstrong, met with President Barack Obama on Monday at the White House. The day before, both Aldrin and Collins said NASA should focus on sending people to Mars instead of the moon. (Image: NASA/Bill Ingalls)