 Astronauts (Lloyd Bridges, Osa Massen, John Emery, Noah Beery, Jr., and Hugh O Brien) blast off to explore the moon on. Because of craft malfunction and some fuel calculations, they end up landing on Mars. On Mars, evidence of a once powerful civilization is found. The scientists determinted that an atomic war destroyed most of the Martians (Who suprsingly look like humans). Those that survived reverted to a caveman like existance.