Abstract
Data from Mariner 5, the Soviet planetary probe Venera 4, and recent ground-based measurements have provided much new information and permitted a great step forward in our knowledge of Venus. Although the data from the various sources generally complement one another very well to provide a fairly detailed picture of the atmosphere of Venus, several serious discrepancies exist that still require clarification. These relate to composition, particularly oxygen and water, and to the surface pressure and temperature. On the positive side, it is now clear that the atmosphere is very dry, with great pressure and high temperature at the surface. It also appears increasingly probable that the greenhouse theory can account for the very high surface temperature. The most likely explanation for the clouds is that they are of convective type consisting of ice crystals and with tops near the 0.2-atm pressure level.
