Inherit the Stars: When they found the corpse on the Moon, wearing a spacesuit, lying in a grave of moon rocks, his identity was a complete mystery. The spacesuit was of a completely unfamiliar design. Then analysis showed that the corpse was 50,000 years old-meaning that he had somehow died on the Moon before the human race even existed. . . .

The Gentle Giants of Ganymede: On another moon, Jupiter's Ganymede, another mystery was found: a wrecked spacesuit, which had been there for millennia, and which obviously was designed for beings larger than the humans of Earth. The mystery seemed insoluble until another ship, manned by the strange humanoid giants arrived, and were very surprised to find humans inhabiting the Solar System. . . .