Letter from Thomas Gold to Dr R clatyton, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois Asks for a re or pre print of his paper on the nitrogen isotopes that Clayton presented in Wales. As he knows, Gold has taken an interest in the very large isotope effects that may well be expected in planetary atmospheres. For Jupiter and Saturn and their inner satellites, the effects could be quite startling. He expects Clayton has noted how large the effect has been for nitrogen on Mars. 5 October 1976