6 of 6

Lunakhod 2

In January 1973 the last rover was sent to the moon's surface—the remote-controlled Lunakhod 2. Like the Soviets' previous vehicle, Lunakhod 2 was an eight-wheeler packed with cameras and sensors, and it featured an internal nuclear heater to survive freezing lunar nights. Because there is insufficient atmosphere on the moon to trap sunlight, bottoms of dark craters near the lunar poles that never receive sunlight are as close to absolute zero as any place in space.



Yet even in these conditions, Lunakhod 2 ran for four months. At that point it was speculated that Lunakhod 2 overheated because of moon dust clogging some of its mechanics.



Still, the whereabouts of Lunakhod 2 have been known for decades; its reflector antenna has been visible to astronomers and other scientists on Earth. This antenna, when a laser is reflected off it, lets scientists monitor size fluctuations. (The Apollo missions also left reflectors on the moon that allow scientists to track its exact distance from Earth, speed, and orbit, but researchers needed another reflector to capture the tiny variations in the moon's size. Understanding that could help lead to a better understanding of exactly what the moon is made of.)



The Lunakhod 2 traveled about 20 miles during its road trips on the moon, sending back climate data, video, and photographs. It roamed the 30-mile wide Le Monnier crater that edges up to the Sea of Serenity dry lakebed—an area adjacent to the famous Sea of Tranquility, where Armstrong and Aldrin walked on the moon's surface. The final observation of Lunakhod 2 was a view of the Fossa Recta trench inside the Sea of Serenity, before its instruments went silent.