The Phobos 2 spacecraft, initially injected into an elliptical orbit around Mars on January 29, 1989, was subsequently transferred, on February 18, 1989, to a nearly circular orbit, close to that of the Phobos moon, with an areocentric radius of the order of 9600 km. The spacecraft remained in this orbit until the end of the mission, on March 27, 1989. This paper summarizes the plasma and wave observations carried out in the night sector of Mars with the plasma wave system (PWS). Embedded in the magnetic field structure of the Martian tail, cold electron enhancements (''tail rays'') with densities in the range 10--65 cm-3 are observed in association with broadband wave activity extending from a few hertz up to several kilohertz; these enhancements appear to have characteristics analogous to enhancements observed at Venus. The ion outflow through the Martian eclipse region is estimated from Langmuir probe measurements to be of the order of 1025 ions/s. ¿ American Geophysical Union 1991