Hi all. Just wanted to say hi to everyone, and ask a couple noob questions. It relates to terraforming mars. All I have read is the Wiki article, so far, so please excuse my ignorance. Anyway, here is the question. If we were to somehow terraform mars, what would keep the atmosphere there, for the long term? I like to think that we could make it stick so long that the planet could one day be covered with plant and animal life, as well as human life. Well, without a working dynamo core to generate a good magnetic field, (since it doesn't have a good enough moon to help spin the core) what would keep the newly generated atmosphere from just blowing off, or drastically thinning, eventually? Due to solar winds and solar flares and all.

We really don't have to worry about our plants killing too much carbon dioxide, as long as we have animals to expel it and volcanos to spew it out in mass quantities. But mars wont be having any volcanoes to help out, will it? The churning core is no longer spinning...

Welcome to BAUT, PhotonFanatic.

I can't give you a solid engineering answer to the atmosphere question, but a friend of mine worked out that if you suddenly provided the moon with a breathable atmosphere, it would linger for something like 10,000 years. (I'll chase him up for the proper figures later - and perhaps how he worked it out.)

Obviously, if the moon can hang on for that long, Mars would have no trouble. On the other hand, giving it an atmosphere in the first place might prove to be a somewhat difficult task.

I think the issue here is that when we're discussing planetary science, we're too used to thinking in terms of millions or billions of years.

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You would also require a magnetosphere, which Mars doesn't have, or the radiation
from our sun kill any chance of life. Think your proposition through Photon.
Nokton.

We could move several bars (as measured on Venus) of Venus' CO2 and one of N2 to Mars and expect it to last on the order of tens of millions of years (replenished as necessary). Retention of hydrogen will always be a problem because the elevated temperature required by terraforming will cause water to "perculate' to the top of the atmospphere, get dissassociated, and facilitate the escape of hydrogen because of the velocity imparted to hydrogen atoms and molecules from the thermal kinetic energy. Some abatement of hydrogen loss may be achieved by having a much thicker Martian atmosphere than the one on Earth such that the velocity from thermal kinetic energy at the top of the "newly formed" Martian atmosphere statistically favors hydrogen retention.

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That's what I was talking about when I said "magnetic field". Maybe I worded it wrong, or maybe they are two different things?

So is this the only real problem? That the magnetosphere isn't going to be there? All the others seem like they could be circumvented at least somewhat feasibly.

When the sun swells up a bunch, will the ice melt and create its own atmosphere? I guess it depends on too many variables that we don't quite understand yet.

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The solar wind isn't a constant blasting gale that'll strip atmospheres away. It's a stream of low energy particle radiation that heats the upper layers of the atmosphere, slightly increasing the rate of escape. The difference in gravity is a far greater issue, an atmosphere of similar temperature to Earth's would experience far more rapid losses, magnetic field or not. And as you note, there is no significant volcanism to replace it. However, if we can terraform Mars in the first place, we can replace atmosphere at rates far greater than losses.

You'd need to import huge amounts of atmosphere, though, and it would require constant maintenance and probably never be as hospitable as Earth...it may even be less hospitable than present-day Mars, due to the more severe weather patterns the thicker atmosphere would support. You would have to deal with rain and snow, ice and high winds, etc.

Enclosed environments would be a much better way to go: A controlled climate, as warm and as high pressure as desired from the very start, while the outside atmosphere remains thin and cold. Weather remains restricted to winds pushing fine dust around, the thin atmosphere poses little obstruction to launching spacecraft, and you preserve valuable deposits of solid water and CO2 which you can mine and convert into propellant, chemical raw material for plastics, or feed into your farms.


Think your objections through, or at least properly research them. First, life can tolerate considerably more radiation most of Earth's surface experiences. More importantly, the atmosphere itself is a very effective radiation shield. Earth goes through periods of essentially no net magnetic field without major extinction events, and in fact a great deal of charged particle radiation goes right through the current magnetosphere and reaches the atmosphere. Mars has lower surface gravity, so an atmosphere of similar surface pressure would be much deeper and be even more effective as a radiation shield. On top of that, Mars receives about half the solar radiation that Earth does...background radiation on a terraformed Mars might very well be lower than that on Earth despite the total lack of a magnetic field.

Constant upkeep. But don't worry, it won't be all that excessive-- a few comets dumped into the atmosphere every few centuries would be plenty. For a society that has developed enough space travel and space-based industry to even begin the early stages of terraforming, that's practically child's play.

No, a sufficiently thick atmosphere provides a surprising amount of shielding, as astronauts who leave the Earth's atmosphere (but were still within the magnetosphere) quickly found out.

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Most terraforming experts are of the opinion that Mars can keep an atmosphere for a million years, but not much longer without replenishing. Hydrogen/water replenishing may be automatic by comet collision. Increasing the average surface temperature of Mars by 20 degrees c = 36 degrees f will not increase the atmosphere loss by much, but that is warm enough for most plants, only at low elevations near the equator, so it will take a million years for plants to reduce the present carbon dioxide significantly. CFCs and other green house gases can be manufactured on the surface of Mars and released into the atmosphere to warm Mars, perhaps 5 degrees c = 9 degrees f. My guess is more is not practical as the power of green house gases has been seriously exaggerated and some green house gases will impede plant growth even in low concentrations. There are some plant varieties that can subsist in the present Mars atmosphere, which has negligible free oxygen, but water, fertilizer and warmer temperatures are needed. I have not heard any believable method for getting significant free oxygen in Mars atmosphere, so it appears oxygen masks for people and animals are the only likely option. The pressure needs to be higher than the present 3 to 6 millibars for humans and most animals and plants, even breathing 98% oxygen. The pressure may eventually increase enough, if we use statites or equivelent moon size mirrors to heat Mars about 20 degrees c. Trace chemicals in the Mars biosphere will have to be removed for healthy plants and animals. In my opinion semi terraforming Mars is almost as costly as semi terraforming the polar regions of Venus. Neil

Oxygen is easy...use plants to convert the vaporized CO2 to O2, and build factories that reduce rock to free O2 and elemental silicon or metals, or just less-oxidized forms. Horrendously expensive, yes, but "easy".

Nitrogen is a bigger issue. Nearest source is Earth, and we're using it. Titan has a lot, but is rather distant. Venus has plenty, a couple Earths worth...perhaps an endless stream of solar sailcraft carrying loads of nitrogen and CO2 to Mars and returning to Venus. Probably one of the more feasible than methods of shipping the stuff...but you're talking about transporting an entire planetary atmosphere. Mars is smaller than Earth, yes, but that doesn't entirely work in your favor, since it has less gravity to compress the atmosphere down...you'll need a much deeper atmosphere to reach a given pressure.


At least there you don't have to import vast quantities of materials from other planets. Well, there's not a lot of water, but that's relatively simple to collect and recycle in enclosed habitats.

Nearly 3% of the Martian atmosphere is nitrogen, so the planet's not completely bereft of it. Potentially, there could be saltpeter deposits on Mars, which would have nitrogen as one of their components. Until we start mucking about the planet in a large way, we won't know for sure.

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What are the chances of kickstarting volcanism? Would drilling into volcanos release anything useful?

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So what? That's 3% of an atmosphere that's less than 1/100th the pressure of Earth's. Plenty to supply enclosed colonies, but the topic of discussion is terraforming, and the thing you need nitrogen for is to bulk up that atmosphere...you're not going to do that using the nitrogen that's already there!

Maybe there's nitrates somewhere, but it's certain there's nowhere near enough nitrogen in any form on the planet to bulk up the atmosphere to even vaguely Earthlike levels, while the solid material of the planet is largely oxygen-containing compounds. Nitrogen is a much bigger issue.