  Using an exact supergravity solution representing the Dp-\bar{Dp} system, it
is demonstrated that one can construct a supergravity analogue of the tachyon
potential. Remarkably, the (regularized) minimum value of the potential turns
out to be V(T_{0})=-2m with m denoting the ADM mass of a single Dp-brane. This
result, in a sense, appears to confirm that Sen's conjecture for the tachyon
condensation on unstable D-branes is indeed correct although the analysis used
here is semi-classical in nature and hence should be taken with some care. Also
shown is the fact that the tachyon mass squared m^2_{T} (which has started out
as being negative) can actually become positive definite and large as the
tachyon rolls down toward the minimum of its potential. It indeed signals the
possibility of successful condensation of the tachyon since it shows that near
the minimum of its potential, tachyon can become heavy enough to disappear from
the massless spectrum. Some cosmological implications of this tachyon potential
in the context of ``rolling tachyons'' is also discussed.
