  In this paper we propose an interpretation of the time series of the RMS
overlap differences of the out-of-plane part $N$ of the orbit of the Martian
polar orbiter Mars Global Surveyor (MGS) over a time span Delta P of about 5
years (14 November 1999-14 January 2005) in terms of the general relativistic
gravitomagnetic Lense-Thirring effect. It turns out that the average of such a
time series over Delta P, normalized to the predicted Lense-Thirring
out-of-plane mean shift over the same time span, is \mu= 1.0018 +/- 0.0053. A
linear fit of the considered time series over Delta P yields a normalized slope
1.1 +/- 0.3 strengthening our interpretation of the determined MGS out-of-plane
features of motion as due to the gravitomagnetic force of Mars.
