It has recently become practical to use the radio emission of the moon and planets as a new source of information about these bodies and their atmospheres. The results of present observations of the thermal radio emission of the moon are consistent with the very low thermal conductivity of the surface layer which was derived from the variation in the infrared emission during eclipses (e.g., Garstung, 1958). When sufficiently accurate and complete measurements are available, it will be possible to set limits on the thermal and electrical characteristics of the surface and subsurface materials of the moon.

Observations of the radio emission of a planet which has an extensive atmosphere will probe the atmosphere to a greater extent than those using shorter wave lengths and should in some cases give otherwise unobtainable information about the characteristics of the solid surface. Radio observations of Venus and Jupiter have already supplied unexpected experimental data on the physical conditions of these planets. The observed intensity of the radio emission of Venus is much higher than the expected thermal intensity, although the spectrum indicated by measurements at wave lengths near 3 cm and 10 cm is like that of a black body at about 600 ` K. This result suggests a very high temperature at the solid surface of the planet, although there is the possibility that the observed radiation may be a combination of both thermal and non thermal components and that the observed spectrum is that of a black body merely by coincidence. For the case of Jupiter, the radio emission spectrum is definitely not like the spectrum of a black-body radiator, and it seems very likely that the radiation reaching the earth is a combination of thermal radiation from the atmosphere and non thermal components.