Realistically, though, I wouldn't expect pressure to vary that much with elevation. Mars' weaker gravity implies that it would vary less than on Earth. However, according to this [1], the pressure does vary a lot by season. That's interesting.

> Surface pressure: 6.36 mb at mean radius (variable from 4.0 to 8.7 mb depending on season)

Surface water might not be readily available on Mars, but ice is present on the surface at the poles, and probably elsewhere in shadowy craters or underground. (Unfortunately, the places with the best access to ice are not great for solar power.)

[1] https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.htm...