Letter from Thomas Gold to Dr Ronald Scott, California Institute of Technology, Pasadena, California Asks if 'the adhesion shown on the target surviving the subsequent landing impact is in accord with the values you chose in your general analysis'. Says that he finds that 'dry rock powders in air will not perform under such circumstances, and more cohesion is needed (and in my view, indeed expected). I am quite confident that the material is somewhat more cohesive than any dry rock powders with which I have experimented'. 27 November 1967