Title: Can Mars support human life? - Quora
Headings: Can Mars support human life?
Can Mars support human life?
Have you been hacked?
Eugene Miya
James Carlisle
Sangeetika Puvvula
Bob Singer
Raginald Mars

Content: Even if you could give Mars an atmosphere as thick as Earth's by impacting comets say, lots of them - it would still be too cold. So in those plans, they also add lots of greenhouse gases as well to keep it warm - and do so continuously into the future, because the "blanket" of Earth's atmosphere is not warm enough for Mars (it gets about half the amount of sunlight that Earth gets). By lots, they mean, mining of the order of a cubic kilometer of fluoride ore every decade in order to make greenhouse gases to keep Mars warm, and you keep that up into the indefinite future. Or you have thin film mirrors in space with the total area of the mirrors equal to the cross section of Mars, of order tens of millions of square kilometers of space mirrors, to reflect sunlight to double the amount it receives. Those again have to be maintained and kept positioned accurately into the indefinite future. And there is lots to go wrong. We have never yet built even a 10 kilometers square living area space station with a closed habitat system. We haven't even built a three person space station able to grow its own food and make all its own oxygen from plants. We are a long way away from the level of knowledge needed for terraforming any planet. And if we bash in and "give it ago", it is an irreversible process as soon you start introducing new life forms to the planet.