Originally Posted by replayrob
From my basic understanding- Mars no longer has a molten iron rotating magnetic core like the earth has- therefore it has no magnetic field and magnetosphere that helps hold the atmosphere to the planet and protects us against solar radiation. Since there's no atmosphere- most of the water has evaporated off into space too. Since there's no way to make the core molten and rotating again- there's just no way to keep a dense atmosphere on mars, no way to keep liquid water on the surface, and no way to protect against lethal radiation. Best case scenario for human habitation of Mars would be living under the surface or on the surface in pressurized structures.
It doesn't seem likely that we'd ever be able to reverse the cause of Mars losing it's magnetic field, atmosphere, liquid water, etc... Mars is basically spent as a first class habitat for humans- but it's useful for natural resources.
It's true that without a protective magnetic field the solar wind would eventually blow the atmosphere out into space, as it's already done on Mars. But there's already an atmosphere - albeit not much of one. The density is about 1% of earth at sea level, or equal to what you'd find about 35 km up. It's just a matter of thickening it by releasing vast amounts of gases. There are lots of ways to do that. It's certainly possible with the technology we already have. You could thicken up the atmosphere many orders of magnitude faster than the solar wind could blow it away.
Then it becomes a matter of changing its composition. That would take much
longer, but with the right mix of biology and botany - taking no more than several hundred years, probably - you could create a breathable atmosphere that could sustain animal life, including humans. And as the atmosphere thickens, the by-product is a rise in temperatures. By then we, meaning the new Martians and their technology, will have evolved to adapt to the stresses and conditions of living there.
As for water, the other mandatory ingredient for life as we know it, there's likely already plenty of it sealed away underground in vast frozen aquifers. As Mars gains more atmosphere and warms up, that water will be released and flow back onto the surface where it can be managed. Or you drill for it.Voilà!
Real, honest-to-goodness terraforming. All eminently doable; we but lack the will.