Sadly, Mars' core has pretty much cooled down, and without a molten core, Mars lacks a magnetoshpere, and thus it is pounded by deadly radiation from the Sun. Mars can never be terra-formed and "colonized", but something small like the Antartic base may be set up there.

The Moon is much closer to the Earth, and travel times and logistics are easier. Return to the Earth's protective magnetosphere is possible, as are radiation shelters, but still the chances of "colonies" on the Moon are pretty slim.

What may be possible is that man tended observatories may be set up on the Moon to deal with the very real danger arising from asteroids and comets striking the Earth. It may be cheaper to set up the telescopes on the Moon rather than in free space.

EP