QUESTION:
Do you expect to use Mars as a landing facility for future exploration to
other planets?

ANSWER from Andrew Petro on August 4, 1997:
Mars will probably not be used as a landing facility for trips to other
planets.  It takes a lot of energy to land and then take off again from Mars
so you probably would not want to land there unless Mars was your actual
destination.  We will probably go directly to the other planets from Earth
orbit.  It may be possible for ships returning to Earth from Mars to refuel
with propellant made on Mars, which will make the round trip more practical.

Andrew Petro, Johnson Space Center, Houston, Texas