Letter from Thomas Gold to Dr L L Hood, Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona, and Dr G Schubert, Department of Earth and Space Sciences, University of California, Los Angeles, California They were very interested in Hood and Schubert's conjecture on the light areas of the Moon. They are enclosing a copy of their survey of the whole surface darkening process, and a discussion of what they believe to be the strongest evidence for the process. 15 October 1979