Exclusive Clip: 'Apollo 18's Spooky Space Mission

ET's got an exclusive clip for one of the summer's last sci-fi thrillers, Apollo 18!

When Apollo 17 was the last manned moon mission, no one could have imagined why... that is, until the US Department of Defense sent two more astronauts on a covert mission to the moon. Shrouded in secrecy, the footage from that fateful mission depicts why NASA denied its authenticity and the real reason no one has ever gone back.

Check out the chilling footage in the video! Apollo 18 lands in theaters Friday, September 2.