In 1970 the Soviet Union put a laser reflector on the moon, carried by a rover. A few months later, it disappeared. Some speculated that the rover had fallen into a crater or parked in such a way as to render the reflector inaccessible. Now, after 40 years on the lunar surface, the reflector has been found.

A team at U.C. San Diego had been searching for it. Earlier this year, NASA’s Lunar Reconnaissance Orbiter camera provided images of the original landing area. A sunlit speck, miles from where the team was looking, turned out to be the rover and reflector. The San Diego team was quickly able to pinpoint the reflector’s location to within 10 meters.

Scientists send laser pulses to the moon and measure signals that bounce back from three reflectors left by Apollo astronauts, along with another Soviet one. This information helps track the moon’s position and orbit. And the researchers say that the rediscovered Russian reflector is particularly useful for studying the moon’s liquid core and testing ideas about gravity. Says team leader Tom Murphy of the reflector, “It’s got a lot to say after almost 40 years of silence.”

—Cynthia Graber

[The above text is an exact transcript of this podcast.]