The conditions leading to the transport of momentum of the shocked solar wind to the Mars magnetosphere are examined. It is argued that planetary pickup ions born in the magnetosheath and scattered across the magnetopause by local turbulent waves carry that momentum and deliver it to the magnetospheric plasma. It is further suggested that as the pickup ions experience momentum scattering interactions with the wave field in the velocity shear adjacent to the magnetosphere they are subjected to a gradual internment within that region of space. The end effect of this phenomenon is that the pickup ions deliver a larger amount of momentum to the local flow than what they can subtract from it. Calculations of the efficiency of the process lead to values of the effective mean free path of the pickup ions of the order of a few hundred kilometers. ¿ American Geophysical Union 1991