Data are given indicating the possiblity of strong solar wind Deimos interaction. Plasma measurements on board the Soviet interplanetary probe Mars 5 showed a drop in ion density and distortion of ion energy spectra in the region behind Deimos at a distance of about 20,000 km. The dimension of Diemos is smaller than the ion hyroradius, and the effect observed may exist in the case of Deimos outgassing. Ion spectra characteristics indicate that outgassing activity is probable. The existence of strong solar wind-Deimos interaction may result in influence on the Martian magnetosphere and bow shock. The dimension of the magnetosphere is maximal when Mars is shaded by Deimos.