Earth: Life, water, air, air pressure, warmth, gravity, sunshine, dirt.

Venus: Water vapor, air pressure, warmth, gravity, more sunshine.

Mars: Dirt.

Mars: dirt, water (likely as brine), air, air pressure, warmth, gravity, sunshine.

You just get a lot of dirt, and a lot less of the others, but brine can be purified, air can be compressed to get pressure, useful minerals can be mined from the soil and rocks, which unlike Venus, isn't under a scorching acid bath.

I.e., just dirt. All else must be manufactured in small spaces, where possible at all.

Gravity is 1/3 normal, period. Sunshine is at 1/2 normal. Warmth is lacking. Air pressure is lethal.

When you have to lie to make it seem appealing, it is the lie that sticks, not the appeal.

I was talking about small spaces all the time! Of course people wouldn't live in the Martin outdoors, but in the Martian underground.

Most things can manufactured most places, with varying degrees of difficulty. A key factor is where you start. My lists were where you start, in each environment. Starting at Earth-normal pressure, Earth-normal temperature, and Earth-normal gravity is advantageous, vs starting with none of those things. Venus has them, Mars manifestly does not.

But even in ideal circumstances, manufacturing Earth-normal gravity on Mars will not be possible.

While I tend to agree with the idea of colonizing a planet as similar as Earth as possible, I also think the barrenness of Mars actually simplifies logistics.

On Venus, you have to deal with high temperatures, acid rain, the bigger gravity well, and the ever-present danger of your floating city falling down. On Mars there's a lot less of everything, but ruling out a meteor, the things you have to deal with are gentler. Not even a dust storm would kill you if it caught you outside in your spacesuit, as it would feel like a breeze.

http://www.mars-one.com/faq/mission-to-mars/what-are-the-ris...