Professor Robert Crater was a reclusive Federation archaeologist and husband to Nancy Crater. In his younger years, he made his career by participating in a ground-breaking survey of an Andorian archaeological dig. Although he was only a junior member of the expedition, a combination of persistence, luck, and occasional flashes of brilliance brought him the most significant finds of the party, which resulted in several important articles. He met Nancy at a conference shortly thereafter, and she was drawn to his sharp mind and the kindly nature he didn't readily show to most people.In 2261, Robert and Nancy began an expedition on M-113 to conduct a survey of the planet's many ruins. Unknown at the time of the Crater expedition, a single surviving member of the salt vampire race continued to live on the planet. It eventually killed Nancy and continued to live along with Robert until 2266. When the USS Enterprise visited for a routine check, Crater was visibly upset and wanted them to leave. When it was discovered that a creature was killing crewmen, James T. Kirk and Spock tried to apprehend him. He resorted to violence but was subdued. He explained about the salt creatures, equating them to the buffalo that was wiped out on Earth. He claimed that the creature was the last of its kind and deserved to live. Robert was eventually killed by the salt vampire aboard the USS Enterprise.