We could start on Mars by building stuff in the canyons first at the lowest possible elevation to increase the air pressure. Then you can dome sections of the canyon and pump up the atmosphere allowing large "outdoor" area.

Would also provide radiation shielding.

Mars air pressure is really low; I don't think building in canyons would have much benefit if you're concerned about reducing the stress of air pressure on the habitat. Building low relative to the surrounding ground though might have benefits related to radiation shielding, though.

The way I usually picture Mars settlements being made is either finding an existing lava tube and creating an airtight seal on the interior, or digging a hole in the ground, erecting a dome (possibly out of blocks made on-site from local materials), and then burying it in dirt. The dome acts as a compressive structure, and you can inflate a habitat on the inside like blowing up a balloon. Either way, people live underground for the benefit of radiation shielding. And either way, the airtight seal of the habitat has something solid for all that air pressure to press against.

I know that it's 1/200th of earth sea level but based on how deep those canyons are you might get 1/20 at the deepest parts. Maybe enough for water to not immediately evaporate.

Reminds me of Out of the Silent Planet by C. S. Lewis, written before anyone had much of a clear idea of what the surface of Mars is really like. There was air and life in the canyons, but everything else was a low-oxygen desert.

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...

I'd love to see some pressure readings from Hellas Basin. It's a full five miles below what scientists say is the average elevation.

Hmm, according to wikipedia, the pressure in Hellas can sometimes get up to 12.4 mbar, and it looks like there are some significant glaciers. Interesting. Tunneling into the ice could be a plausible way to build a Mars habitat...

https://en.wikipedia.org/wiki/Hellas_Planitia

Sounds like a plan. GO GO GO!

I think you're underestimating the value of "you can breathe the air" and "water is easily available via melting snow" when comparing it to Antartica.

I'm suggesting that Mars may be a more hospitable place than the moon, not more hospitable than Antarctica. Antarctica is a much easier place to survive than Mars or the moon, but the long-term benefits of establishing a permanent human presence are less. We also already have a lot of people living in Antarctica; according to wikipedia, there are about 40 year-round bases, and the population varies from about 4,000 in the summer to about 1,000 in the winter.