  We study some of the effects that magnetic turbulent fluctuations have on the
dynamics of pickup O+ ions in the magnetic polar regions of the Mars
ionosheath. In particular we study their effect on the bulk velocity profiles
of ions as a function of altitude over the magnetic poles, in order to compare
them with recent Mars Express data; that indicate that their average velocity
is very low and essentially in the anti-sunward direction. We find that, while
magnetic field fluctuations do give rise to deviations from simple ExB-drift
gyromotion, even fluctuation amplitudes much greater than those of in situ
measurements are {\it not} able to reproduce the vertical velocity profile of
O+ ions. We conclude that other physical mechanisms, different from a pure
charged particle dynamics, are acting on pickup ions at the Martian terminator.
A possibility being a viscous-like interaction between the Solar Wind and the
Martian ionosphere at low altitudes.
