Green Light for Giant Impact

Abstract

Abstract The Mariner 10 mission to Mercury in 1974 showed that planet’s face to be as heavily cratered as the Moon, helping to persuade scientists to accept the fundamental role of impact in the history of the solar system. Like many scientific ideas, giant impact had been proposed in the 1940s but had been ignored. In the 1980s, scientists took the idea up again in a burst of activity. A 1984 conference found that giant impact was at least tentatively accepted by most lunar scientists. Many began to regard such collisions as inevitable in the early solar system, but that did not necessarily mean that one caused the Moon. Nevertheless, as one science reporter summed up, the giant impact hypothesis had “breathed new life into a long-stagnant field.”