Runaround

In 2015, Powell, Donovan and Robot SPD-13 (also known as "Speedy") are sent to Mercury to restart operations at a mining station which was abandoned ten years before. They discover that the photo-cell banks that provide life support to the base are short on selenium and will soon fail. The nearest selenium pool is seventeen miles away, and since Speedy can withstand Mercury’s high temperatures, Donovan sends him to get it. Powell and Donovan become worried when they realize that Speedy has not returned after five hours. They use a more primitive robot to find Speedy and try to analyze what happened to it.