QUESTION:
Will the crew spend their entire trip to Mars on the spacecraft that
launched them into space or will they be spending it in the habitation
module? Will the habitation module be used on Mars?

ANSWER from Andrew Petro on March 29, 1999:
There are a lot of possibilities for how a mission to Mars will
eventually work. But most likely, the crew will be launched from Earth
in one type of vehicle (maybe something like the Space Shuttle) then
travel to Mars inside a space habitation module, then descend to Mars in
a Mars landing vehicle and then live on Mars in a surface habitat module
(which may be part of the landing vehicle or may be landed separately),
then ascend from Mars in an ascent vehicle (which could be the same as
the landing vehicle or separate - but it would need to be small), then
travel back to Earth in a space habitat module (probably the same one
they traveled out to Mars in, and then either their habitat module would
get back in Earth orbit and something like the Shuttle would come pick
them up and take them back to Earth or they would get into a small
capsule, separate from their habitiat module and return directly to the
Earth.  So you can see their would be several different spacecraft and
probably more than one habitation module. Earth orbit and Mars orbit can
be used as staging points where the crew can transfer from one vehicle
to another.

Andrew Petro
Johnson Space Center