QUESTION:
Are there places on the Earth where the atmospheric conditions are similar
to those on Mars? For example, it dips to -100F deg in the antarctic.  Does
7mb pressure compare to the peak of Mt. Everest? If not, to what altitude of
the Earth's atmosphere does it correspond?

ANSWER from Mike Mellon:
The top of Mt. Everest is at about 8.8 km above sea level. At this altitude
the atmospheric pressure is roughly 310 mb (1000 mb is about sea level
pressure). This is still significantly higher than Mars surface pressures.
On Earth, Mars surface pressures would be reached at an altitude of roughly
30 to 35 km. I believe this is higher than any aircraft can fly on Earth,
but much lower than the typical orbital altitude of the space shuttle.