Well, but then, if CO2 is just going to go above the SF6 layer, it is going to be blown in space, wouldn't it?
Some of it might, but obviously not all, since 95% of the current Martian atmosphere is CO2. Should just make it thicker and denser (as seen by the various strategies that involve sublimating all the Martian dry ice *without* SF6).
As I said, one study said that melting it all should bring the total pressure up to about 0.3 bar, comparable to Mt. Everest. Obviously not breathable, since it'd be essentially 99% pure CO2, but you could get around the surface without a pressure suit. Daytime temperatures in the southern summer might even be warm enough to not need protective gear (although you'd still want your skin covered, as the air would likely be highly dessicating, with humidity levels that would make the Sahara look like a jungle).
A somewhat more useful side-effect is that atmospheric flight would be easier with a thicker atmosphere (today's
xkcd what-if discusses that in detail), making it far more viable to explore from the air. At 0.3 bar, the airspeed problem alluded to becomes significantly less (a factor of 1.82:1 rather than the roughly 10:1 it currently is). So instead of having to do Mach 1 to get off the ground, you only need about 110 knots.
EDIT:
But aiming an asteroid at the pole is kinda hard no?
Edit: Here is the paper RedKing.
Glancing over the paper, those aren't really new ideas...the orbital mirrors and asteroid impact ideas were around when I was a kid. (Not that using SF6 is amazingly novel either, but it's considerably less well-known). That paper makes some very odd assumptions though. Like this:
If the asteroid is made of NH3, specific impulses of about 400 s can be attained, and as little as 10% of the asteroid will be required for propellant.
Maybe my astrogeology is out of date, but I'm not aware of asteroids having particularly large concentrations of ammonia to use as rocket fuel. Yes, there have been some carboniferous meteorites recovered with ammonia in them, but they're the exception rather than the rule and it's not in an easily accessible form. Seems like a comet would be a better candidate, other than the fact that they tend to already have a significant velocity rather than kind drifting in a wide orbit. Best you could hope for would be to find one that had a near-miss with Mars coming up, and attach some boosters to it to turn that near-miss into a hit. One potential benefit would be water ice, but most of that water would be lost relatively quickly afterwards through UV disassociation and subsequent loss of hydrogen through the upper atmosphere. Plus you're adding some nasty volatiles like ammonia and methane.
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Topic: Quick physics/chemistry question (Read 2811 times)