Early in the 1960s (probably 1960 or 1961), before the Ranger missions to the Moon, NASA convened five eminent scientists to discuss what was known about the Moon. The panel, Robert Jastrow, Harold C. Urey, Thomas Gold, Gerard de Vaucouleurs, and Nicholas Christofilos represented a substantial fraction of the entire community working in the area of lunar and planetary science at the time.
What was known about the Moon before probes were sent there? Very, very little. Still under debate was whether the craters were volcanic or due to impacts, whether the “seas” were lava flows or basins of fine dust, whether the surface was solid or a sea of dust into which landers would disappear, how the Moon formed, and whether the Moon was geologically active or a cold rock. How much would change in the decade after this conversation!