Neutral gas temperatures inferred from top-side plasma scale heights of electron density distributions obtained from observations by US and USSR Mars missions imply a much higher dependence on solar activity (expressed by the 10.7 cm radio flux F10.7) than that found for Vunus. This dependence, however, does not appear to be consistent with the observed solar cycle dependence of ionospheric peak plasma densities. The reason for this discrepancy seems to lie in the fact, that photochemical equilibrium applies only to altitudes below 170 km, whereas topside scale heights are usually derived for a much greater altitude range and thus may be modified by transport and other processes. If scale heights are obtained by matching a Chapman-layer to plasma density profiles near the ionospheric peak, the derived neutral temperatures show a much weaker dependence on F10.7, in fact one essentially the same as for Venus. Thus, the response of the upper atmosphere of Mars, at least near the ionospheric peak, appears to be virtually identical to that of Venus. ¿ American Geophysical Union 1989