Many people can accept the possibility of a permanently staffed base on Mars, or even the establishment of large settlements. However the prospect of drastically changing the planet's temperature and atmosphere towards more earthlike conditions, or "terraforming" seems to most people to be either sheer fantasy or at best a technological challenge for the far distant future.
But is this pessimistic point of view correct? Despite the fact that Mars today is a cold, dry, and probably lifeless planet, it has all the elements required to support life: water carbon and oxygen (as carbon dioxide), and nitrogen. The physical aspects of Mars, its gravity, rotation rate and axial tilt are close enough to those of Earth to be acceptable and it is not too far from the Sun to be made habitable.
In fact computational studies utilizing climate models suggest that it could be possible to make Mars habitable again with foreseeable technology. The essence of the situation is that while Mars' CO2 atmosphere has only about 1% the pressure of the Earth's at sea level, it is believed that there are reserves of CO2 frozen in the south polar cap and adsorbed within the soil sufficient to thicken the atmosphere to the point where its pressure would be about 30% that of Earth. The way to get this gas to emerge is to heat the planet, and in fact, the warming and cooling of Mars that occurs each Martian year as the planet cycles between its nearest and furthest positions from the Sun in its slightly elliptical orbit cause the atmospheric pressure on Mars to vary by plus or minus 25% compared to its average value on a seasonal basis.
We can not, of course, move Mars to a warmer orbit. However we do know another way to heat a planet, through an artificially induced greenhouse effect that traps the Sun's heat within the atmosphere. Such an atmospheric greenhouse could be created on Mars in at least three different ways. One way would be to set up factories on Mars to produce very powerful artificial greenhouse gasses such as halocarbons ("CFC's") and release them into the atmosphere. Another way would be to use orbital mirrors or other large scale power sources to warm selected areas of the planet, such as the south polar cap, to release large reservoirs of the native greenhouse gas, CO2, which may be trapped their in frozen or adsorbed form. Finally natural greenhouse gases more powerful than CO2 (but much less so than halocarbons) such as ammonia or methane could be imported to Mars in large quantities if asteroidal objects rich with such volatiles in frozen form should prove to exist in the outer solar system.
Each of these methods of planetary warming would be enhanced by large amounts of CO2 from polar cap and the soil that would be released as a result of the induced temperature rise. This CO2 would add massively to the greenhouse effect being created directly, speeding and multiplying the warming process.
The Mars atmosphere/regolith greenhouse effect system is thus one with a built-in positive feedback. The warmer it gets, the thicker the atmosphere becomes; and the thicker the atmosphere becomes the warmer it gets. A method of modeling this system and the results of calculations based upon it are given in the sections below.
I fear once NASA or a country announces that terraforming mars will be possible, it will be the space race all over again. Except with more countries than the US and Russia. 'Who can develop the first settlement on mars', 'who can benefit the most from doing this', 'How can they do this' etc.
Something about a big industrialized country making settlements or colonies on other planets doesn't seem right to me.