  We derive synthetic electrical conductivity, seismic velocity, and density
distributions from the results of martian mantle convection models affected by
basin-forming meteorite impacts. The electrical conductivity features an
intermediate minimum in the strongly depleted topmost mantle, sandwiched
between higher conductivities in the lower crust and a smooth increase toward
almost constant high values at depths greater than 400 km. The bulk sound speed
increases mostly smoothly throughout the mantle, with only one marked change at
the appearance of $\beta$-olivine near 1100 km depth. An assessment of the
detectability of the subsurface traces of an impact suggests that its signature
would be visible in both observables at least if efficient melt extraction from
the shock-molten target occurs, but it will not always be particularly
conspicuous even for large basins; observations with extensive spatial and
temporal coverage would improve their detectability. Electromagnetic sounding
may offer another possibility to investigate the properties of the mantle,
especially in regions of impact structures. In comparison with seismology and
gravimetry, its application to the martian interior has received little
consideration so far. Of particular interest is its potential for constraining
the water content of the mantle. By comparing electromagnetic sounding data of
an impact structure with model predictions, it might also be possible to answer
the open question of the efficiency of extraction of impact-generated melt.
