The high-resolution data of the electric field observations performed by the plasma wave system (PWS) during some of the Martin bow shock intersections by Phobos 2 were analyzed. Plasma and wave detectors are very useful instruments for locating the shock transition region and studying structures in the upstream region, such as the foot or the electron foreshock. The electron plasma oscillations that develop in the latter give access to the plasma density of the solar wind. Shock surface models derived from the PWS data are compared to those obtained by other authors, and attention is paid to similarities and differences between the electric field measurements obtained for Mars, Venus, and Earth. ¿American Geophysical Union 1991