QUESTION:
When your probe gets close enough to Mars to see anything, what are
you expecting to find? Water? Breathable air?

ANSWER from Jack Farmer on February 11, 1997:
Let me complete the answer to your questions.  Water is unstable
on the present surface of Mars because the atmospheric pressure is too low
that water only exists as vapor in the atmosphere, or as ice in the ground
or at the poles.  In other words, there is no liquid water at the surface
today on Mars.  Without liquid water, it is hard to imagine life.  But Mars
appears to have had lots of water earlier in its history, at a time before
it lost its atmosphere.  In going back to Mars, we hope to discover some of
the rocks that formed in association with water during that early period to
look for evidence of former Martian life as fossils.

As noted above, the atmosphere of Mars is very thin (~7.5 mb, compared to
1000 on the Earth) and it is composed of more than 95% carbon dioxide.
There is no oxygen (to speak of) in the atmosphere of Mars, and so it
cannot at all be considered breathable for humans.  In fact, we have no
evidence that the atmosphere of Mars has ever really been "breathable".
But microorganisms can "breathe" lots of different gases, including carbon
dioxide, methane, sulfide and other gases that are all lethal to humans.
So early on, when Mars had a denser atmosphere, it is quite possible there
were organisms to take advantage of whatever was there in the atmosphere. -