Crash course: Millions of Americans were glued to their TV sets on March 24, 1965 to watch Ranger 9 transmit video of the final 17 minutes (shown here speeded up) of its dive into the moons crater Alphonsus. The video begins with Ranger 9 at a distance of about 1,477 miles from the moon and ends with impact inside the 67-mile-wide crater. Video: NASA (0:15)