From a thorough modeling of the altitude profile of meteoric ionization in the Martian atmosphere we deduce that a persistent layer of magnesium ions should exist around an altitude of 70 km. On the basis of the estimated meteoroid mass flux density, a peak ion density of ~104 ions cm-3 is predicted. Allowing for the uncertainties in all of the model parameters, this value is probably within an order of magnitude of the correct density. Of these parameters, the peak density is most sensitive to the meteoroid mass flux density which determines the source function for Mg from the ablating meteoroids. Unlike the terrestrial case, where the metallic ion production is dominated by charge-exchange of the deposited neutral Mg with the ambient ions, Mg+ in the Martian atmosphere is produced predominantly by photoionization. The low ultraviolet absorption of the Martian atmosphere makes Mars an excellent laboratory in which to study meteoric ablation. Resonance lines in the ultraviolet that cannot be seen in the spectra of terrestrial meteors may be visible to a surface observatory in the Martian highlands. ¿ 2000 American Geophysical Union