I was nearly 16 when Neil Armstrong first stepped onto the moon in 1969, and like most Americans who were alive at the time, I will never forget that moment. But I also remember another earlier space-related milestone equally well. On July 31, 1964, an unmanned space probe called Ranger 7 slammed into the moon at more than 5,800 miles an hour. The crash destroyed the spacecraft, of course, but the mission was a complete success: As it plunged to its death, Ranger snapped a series of photographs of the lunar surface. And while the last one, shot from an altitude of about 1,700 feet, could only be partially transmitted before final impact a fifth of a second later, it showed craters just a couple of feet in diameter.
When I saw that image in the newspaper, I was blown away. Until that moment, the only way to photograph the moon was from Earth, through a telescope—and the most powerful telescope in existence at the time couldn't see surface details less than a mile across. Now, for the first time in history, we'd gotten a close-up look at another world.