  The year 1996 will mark the initiation of a number of new space missions to
the planet Mars from which we expect to obtain a rich set of data, including
spacecraft radio tracking data. Anticipating these events, we have analyzed the
feasibility of testing a violation of the strong equivalence principle (SEP)
with Earth-Mars ranging. Using analytic and numerical methods, we have
demonstrated that ranging data can provide a useful estimate of the SEP
parameter $\eta$. Two estimates of the predicted accuracy are quoted, one based
on conventional covariance analysis, and the other based on ``modified worst
case'' analysis, which assumes that systematic errors dominate the experiment.
If future Mars missions provide ranging measurements with an accuracy of
$\sigma$ meters, after ten years of ranging the expected accuracy for the
parameter $\eta$ will be of order $\sigma_\eta\approx (1-12)\times
10^{-4}\sigma $. In addition, these ranging measurements will provide a
significantly improved determination of the mass of the Jupiter system,
independent of the test of the {\small SEP} polarization effect.
