Anti-Greenhouse Gas substitute?

[Girlinhat]

Stars already measure their luminosity and size, so that's one thing already in place...  I'd like more complex terraforming, especially water.  I love the idea of "ice pushers" who ferry the rings of saturn back over to your new lunar colony to improve the hydrosphere.  The only issue I can forsee is if atmospheres bleed off, then you might find water impossible to preserve and all games will become a race to find the most outlying world with no solar wind and hide there.  But with Steve's other foresights, I doubt he'd let it come to that point.

[Sleepymoon]

Stars already measure their luminosity and size, so that's one thing already in place. . .   I'd like more complex terraforming, especially water.   I love the idea of "ice pushers" who ferry the rings of saturn back over to your new lunar colony to improve the hydrosphere.   The only issue I can forsee is if atmospheres bleed off, then you might find water impossible to preserve and all games will become a race to find the most outlying world with no solar wind and hide there.   But with Steve's other foresights, I doubt he'd let it come to that point.

Since most planets in the solar system have managed to hold on to some atmosphere and water for the last 4 billion years I don't think preserving it will be a problem unless the mechanics get really screwed up.

[Thiosk]

Venus has a magnetic field, as do earth and the gas giants.  Mars and mercury do not.  Neither have an atmosphere worth writing home about.  Between the lack of magnetic field and low mass (resulting in a low escape velocity for gas molecules), terraforming mars is a losing game, and the atmosphere will have to be regenerated continously, rather than a one-step-and-new-permanent-earth strategy.

Terraforming mercury would be a disaster for that reason, which is why i would say that star proximity and luminescence could combine to really blow the air off a planet without a magnetosphere in a shorter period of time.  At least, it makes a case for continuous terraforming!    (the planet would have to be mercury like for this to be a really big deal, imo)

[Yonder]

Since most planets in the solar system have managed to hold on to some atmosphere and water for the last 4 billion years I don't think preserving it will be a problem unless the mechanics get really screwed up.

The problem is that in the case of Mars "some" atmosphere is .59% atm, and that's the most atmosphere on a non-protected body! The only bodies in the solar system with a non-negligible (for a human being) atmosphere are either protected by their own magnetic field, or the very large magnetic fields of their gas giant parents. Now the Solar System also doesn't have any large heavy planets in the outer solar system (Venus/Earth or bigger) so I suppose it's possible that a large, heavy planet that was far enough away from its Sun may have an appreciable atmosphere. The problem with that is that both the solar wind and the heat from the sun scale down at the square of your distance from the sun. I am guessing that the only way to have both an atmosphere and not freeze to death is to have a protective magnetic field.

[Mel Vixen]

The problem is that in the case of Mars "some" atmosphere is .59% atm, and that's the most atmosphere on a non-protected body! The only bodies in the solar system with a non-negligible (for a human being) atmosphere are either protected by their own magnetic field, or the very large magnetic fields of their gas giant parents. Now the Solar System also doesn't have any large heavy planets in the outer solar system (Venus/Earth or bigger) so I suppose it's possible that a large, heavy planet that was far enough away from its Sun may have an appreciable atmosphere. The problem with that is that both the solar wind and the heat from the sun scale down at the square of your distance from the sun. I am guessing that the only way to have both an atmosphere and not freeze to death is to have a protective magnetic field.

And even then most of the moons of gasgiants are just a bunch of rocks without atmosphere. Iirc it was bacause titan is one of the outermost moons of its giant that it has an actual Athmosphere.

All in all the distance to the star also has an impact if a object can hold gases. The shorter the distance the stronger the Solarwind. The venus has the advantage of constantly generating new gases for its athmosphere but the lighter stuff like helium or Hydrogen is almost not findable in its athmosphere.

[Sleepymoon]

Mercury has quite a strong magnetic field and Venus' is incredibly weak, so a magnetic has little to do with atmospheric pressure.

[Person012345]

Mercury has quite a strong magnetic field and Venus' is incredibly weak, so a magnetic has little to do with atmospheric pressure.

No, there is a correlation. Although it's not as simple as "strong magnetic field = more atmosphere". Mercury, although it has a strong field, is very close to the sun. It bears the full force of the solar wind and during solar flares and such, it has it even worse. Venus is losing atmosphere, but it's losing mostly hydrogen, oxygen and helium (it once had water like earth, but it evaporated then got blown away). However, it has an induced magnetic field, and the ionosphere protects some of the atmosphere. The magnetic field is a factor but it's not the only factor in determining atmospheric pressure. Although whether a planet without a magnetic field could have a breathable atmosphere...

[Thiosk]

I was incorrect about venus's magnetic field (i could have sworn it had one) but can you really call mercury's field strong?  Mercury has a pretty weak field (what, ~1% earth?).  Or is the strong/weak division more to do with how it deflects solar wind than magnitude relative to earth (the lunar field does not direct wind around it)

I guess its probably wise to avoid too detailed treatment of planetary science, when really, so little is known about earth, let alone the billions of other worlds in the galaxy.

[Person012345]

Well, it's strong enough, especially considering mercury's small size. The solar wind is what causes atmosphere loss without a field and it's strong enough to deflect it, so...

[metalax]

Well, it's strong enough, especially considering mercury's small size. The solar wind is what causes atmosphere loss without a field and it's strong enough to deflect it, so...

Not entirely, you will still have atmosphere escape even with a massive magnetic field. Atmosphere loss is due to the fact that a gas at a particular temperature has it's molecules at a distribution of speeds, and for each molecule there is a corresponding speed that is sufficient for it to escape from the planets gravity. Hence the high energy(high speed) tail of the distribution past this escape speed allows molecules to escape. Usually this will only occur at the edge of the atmosphere as molecules lower down are more likely to colide with other gas molecules and lose the energy to escape.

What the solar wind does is to help increase the number of molecules that have energies(speeds) over that needed to escape, and also remove the escaped molecules away from the planet reducing the chance of another escaping molecule impacting and loosing the energy it would need to escape. The other way to increase the rate of atmosphere loss is to increase the temperature of the atmosphere.

The magnetic field, or lack of it, effects how much effect the solar wind will have on the atmosphere of a planet. Also planets a large distance from their star will feel relatively little effect from the solar wind even without a magnetic field as the solar wind drops rapidly with distance.