Charlize Theron and Idris Elba star as space explorers in "Prometheus," a mysterious thriller that provides some loose back story to the 1979 science-fiction classic "Alien." (20th Century Fox via Associated Press)

Charlize Theron and Idris Elba star as space explorers in "Prometheus," a mysterious thriller that provides some loose back story to the 1979 science-fiction classic "Alien." (20th Century Fox via Associated Press)