The Sudbury Structure as a terrestrial mare basin

A review is presented of the origin, development, and current status of the hypothesis that the Sudbury Structure of Ontario, Canada, is a deformed Precambrian impact crater analogous to the circular lunar maria. Impact and isotopic modeling studies have shown that the Sudbury igneous complex may be largely impact melt rather than internally generated magma. The analogy between lunar maria and the Sudbury Structure, though petrologically wrong, is valid to the extent that both classes of structure were initially formed by impact.