Volatile element influx on Venus from cometary impacts

Several different reasonably concordant methods of estimating the flux of carbonaceous chondrite and cometary material (both meteoric dust and comet nuclei) through the inner solar system are shown to imply that such sources may have a dominant effect on the present abundances of several important constituents of the atmosphere of Venus. In particular, the entire supply of hydrogen compounds on Venus may owe its origin to infall of such material. The escape rate of atomic hydrogen may be in approximate balance with the influx rate of hydrogen in the forms of bound meteoritic water and cometary ices. I suggest that the atmospheric inventories of H, S, Cl, F and possibly N on Venus are provided by infall, and need not be endogenous to Venus.