QUESTION:
Do you think that the rocks that we investigate on Mars would rust in 
our atmosphere due to the mineral content of the rocks and the 
composition of our atmosphere?

ANSWER from Ted Roush on March 20, 1997:
The Earth has abundant water at its surface both in the liquid and gas 
phases.  As a result iron-bearing minerals rapidly become oxidized, or 
rusty.  The current climate on Mars can not sustain liquid water at the
surface or appreciable amounts of water vapor in the atmosphere.
Nonetheless, a variety of evidence suggests that the minerals on Mars
would readily "rust" in the Earth's atmosphere.  In fact, these same
studies suggest that "rust" is present on Mars and is responsible for 
the Mars' reddish color when viewed through a telescope.