QUESTION:
I read that there is a seasonal darkening of the surface(as viewed from
Hubble telescope) Is this the result of the slight bit of moisture that
melts or sublimes from the pole area causing oxidation of the surface?

ANSWER from Bob Haberle on August 7, 1997:
The explanation you offer for the seasonal darkening was popular before the
spacecraft era began in the 1960's. Indeed some speculated it was caused by
the growth of vegetation during spring. But we now know that the darkening
is caused by the winds. The winds in spring and summer are quite strong near
the edge of the retreating polar cap and they scour the surface removing
much of the fine dusty bright material exposing a dark underlying bedrock.
Then in fall and winter, the dust returns and settles onto the surface
closing the cycle.

ANSWER from John L. Callas on December 5, 1996:
We do not expect the external or internal appearance of Mars to change,
with the exception of seasonal events like the great dust storms that can
completely cover the planet from time to time.