Mariner II: Preliminary Reports on Measurements of Venus: Charged Particles

Abstract
There was a complete absence of charged particles associated with the planet Venus at radial distances as small as 41,000 km on the sunward side of the planet. This result is taken to mean that the magnetosphere of Venus, if any, does not extend to that great a distance. The most plausible interpretation is that (MV/ME) </= 0.18, where MV and ME are the dipole magnetic moments of Venus and Earth, respectively. The results are consistent with MV/ME = 0. Certain qualifications prevent this interpretation from being a definitive one.