[doc30]

If you want to terraform Mars, the first thing you have to do is crank up the gravity to a level that will sustain an atmosphere dense enough to breathe.

I am amazed at how many people think we just need to warm the planet and add atmosphere to get a decent pressure and temperature at the surface. What they fail to understand is that a higher gravity is needed. With the current gravity, warming the planet will result in a loss of atmosphere. With a higher temperature, the Boltzmann distribution of gas molecule speeds will have the high speed tail stretching well past escape velocity with the current gravity on Mars. Warmer Mars = less atmosphere. Or you could jusr dig really, really deep holes so the atmosphere would be of satisfactory pressure. Colonists on Mars would live in deep 'hobbit holes'. The hole depth would increase protection from cosmic radiation, too.

[Old Student]

"What they fail to understand is that a higher gravity is needed. With the current gravity, warming the planet will result in a loss of atmosphere. With a higher temperature, the Boltzmann distribution of gas molecule speeds will have the high speed tail stretching well past escape velocity with the current gravity on Mars. "

Drop enough small asteroids on Mars, (and I'm talking a LOT of them!) and increase the mass while building up the gas pressure and temp, all at once... Of course, we probably ought to look the place over rather carefully first, as there isn't much that would survive the "rain" we caused. (Simplistic solutions for simplistic people...)