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Preliminary results of ion and electron plasma measurements near Venus are presented and discussed. The data were obtained with wide‐angle plasma analyzers carried on the Venera 9 and 10 spacecraft. On the basis of 33 bow shock crossings the position of the shock is quite stable and agrees well with theoretical predictions of Spreiter et al. with H/r0 = 0.01 and a stagnation point altitude of ∼500 km. This observation lends strong support to the assumption that the solar wind interacts with the upper ionosphere of Venus and not with a planetary magnetic field. These spacecraft are the first to explore the optical umbra of Venus. Close to the planet a stable population of electrons and an ill‐defined population of positive ions were found; this region is called the corpuscular umbra. The corpuscular umbra and the transition region are separated by a zone which contains both positive ions and electrons and is characterized by a flow velocity reduced in comparison with that of the transition region. This zone is called the corpuscular penumbra. The distribution of plasma density behind the bow shock (including the optical umbra of the planet) is given, and the existence of a Venusian plasma magnetic tail is revealed.

Results of measurements of boundary positions and characteristics of the transition layer behind the Martian bow shock are presented. For the first time, measured characteristics of the plasma formation located behind the inner boundary of the transition layer on the antisolar part of near‐Martian space are considered. The possible nature of this formation is discussed and some considerations in favor of its interpretation as the plasma sheet in the Martian magnetospheric tail are presented.

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