Makin' Atmo

Just in case you never saw Total Recall, I'll spare you some very lame special effects of people's blood boiling and their eyeballs exploding.

The reason your blood would boil and you'd suffocate on Mars is the lack of atmosphere.  The problem is worse than lack of breathable air; it's lack of enough air.  Without a nice soggy Earth-weight blanket of atmo squeezing down on you, your blood would explode out of your body.  The atmo on Mars is about 1% the thickness of our own.  To survive on Mars we'll need to do more than change the mere composition of the atmosphere - (which right now is whisker-thin and mostly carbon dioxide) - it's even more crucial that we get some heft.
 
The easiest way, according to me, is to smack Mars with a couple small, icy NEAs, or near earth asteroids.  If we can guide at least one into Olympus Mons, the biggest volcano in the solar system, we might get a bit of volcanic activity (it looks as if there's still a bit of geothermic activity in the Mars core) which could add heat, a dust cloud to hold in the heat, and even more water.  With a strike or two you could get lots of atmo and if you're ready to build on that you might be able to start creating a true atmosphere - or a portion of one.  It doesn't need to be Earth-sized.

Mt. Everest on Earth has about 1/3 the atmo of sea level, and sherpas can breathe there.  But 33% is a lot more than 1%.  

According to Nat Geo, Sherpas (well, Tibetans) "...have at least three genes that are different than the rest of us on the planet, giving them a unique ability to adapt to hypoxic environments. They don’t have bigger lungs, they don’t breathe harder, they don’t have more oxygen in the bloodstream, they just appear to have a more efficient engine—and oxygen that gets to the muscles is more readily used," And these are just plain old human genes, which are relatively easy to build into a population.

Beyond that, other gene edits could adapt us even better to conditions on Mars.  But even then, we're going to need a much heavier atmo blanket.

How much atmo can a 'steroid at if an atmo aster'ed at?

Sorry.

This is the part where I chase astrophysicists around.  I've got a lead on one, and I'll post the interview with him in a week or two.