Absorption and reflection of radio waves in the Martian ionosphere

Radio wave absorption in the Martian ionosphere has been predicted and tested against MARSIS radar observations. Models of the ionosphere densities and of absorption in a CO 2 neutral atmosphere were used. The appearance of ground reflections in the MARSIS observations is shown to be consistent with predictions of reflection and absorption of radio waves in the ionosphere. It is concluded that the secondary density maximum, known to be typically present below the primary density peak, contributes considerably to the absorption and thus to the appearance of ground reflections. It is the first time predicted radio wave absorption in a CO 2 planetary atmosphere has been tested against actual observations.