I am given to understand that the earth’s magnetic field has been responsible for, among other things, blocking out the sun’s most dangerous emissions and preventing the solar wind from, in effect, blowing away the atmosphere. I am also told that part of the reason that Mars’ atmosphere is so thin is that its weak magnetic field is unable to prevent atmospheric molecules from being carried away by particles from massive solar storms. If that is the case, then won’t teraforming Mars be problematic? How will greenhouse gases, intended to warm up the place and thicken the atmosphere, be protected from the sun’s periodic eruptions?
Mars also has such a thin atmosphere becuase it is so small, like half the size of Earth IIRC. Our atmosphere is actually leaking away very slowly, at least the hydrogen on the outer most parts is. There is not enough of a gravitational force to hold the most energetic particles. But that doesn’t matter so much because it replenishes itself from the Earth. Now for smaller masses, like Mars, the kinetic energy required for escape velocity is a hell of a lot smaller and so the amount of atmosphere it can hold is much smaller.
But as for protection from solar radiation, you’ve got me there. Either Mars is far enough away that it does not recieve high enough doses of the stuff or any manned expedition better bring some sunscreen, factor one million should cover it.
One big issue with the lack of a magnetic field is that the Earth’s MF traps charged particles from both solar emissions and cosmic rays, sending many of them into the Van Allen Belts or funnelling them over the magnetic poles (auroras). Then the thick(er) atmosphere does the rest of the work. So there by itself is another challenge to the survival of the terraformed ecosystem. (As to sunscreen, that’s yet another point: it’s the ozone layer that does most of the UV blocking on Earth, Mars does not have an O3 layer and merely increasing the O2/CO2/H2O partial pressures to survivable levels does not necessarily create one.) And yes, the lack of that shield plus the low gravity means there would be more of a solar wind “blowout” of the upper atmosphere. Mars apparently went (mostly) geologically inert a while back, which would mean near no replenishment of the atmosphere (On Earth, some gases are replenished volcanically; that plus biological cycling of O2, CO2 and N2, are enough to maintain under our gravity conditions)
A terraformed-martian atmosphere may or may not be extractable from Mars itself, but it could likely require that it be seeded, probably by hitting Mars with redirected cometary cores (and once you get the technology to redirect cometary cores to his a specific place on A planet, you can redirect them to hit specific places on ANY planet… think about it :eek: )
In short, yes the lack of a MF on Mars is a major challenge to terraformation.
Might it might be possible to create an adequate magnetic field artificially? If the technology exists to build synchronous orbit “tethers”, then you could build a superconducting ring all around Mars in orbit.