How quickly would Mars loose its atmosphere?

[Menninger]

Besides low gravity and high doses of radiation, one of the more intractable difficulties in terraforming Mars is that if we build its atmosphere back up, then presumably it would lose it again via the same mechanisms it lost it the first time (ie solar wind, warmth, and low gravity).

However, this may or may not occur quickly enough to really matter to prospective terraformers. Given that it takes considerable atmospheric pressure to allow for the existence of liquid water, and as the general view seems to be that Mars had liquid water during its Noachian and Hesperian eons, it seems logical to suppose that it takes millions of years for Mar's atmosphere to become mostly lost. So imports of gases that mimic the rate outgassed by volcanoes during those eons are sufficient to keep Mar's atmosphere dense indefinitely.

Am I missing something here?

 

[Simon Bridge]

Outgassing rate depends on the atmosphere, it's temperature and pressure and so on.
But it certainly was a very long time for the original Martian atmosphere to be lost.
Getting Mars a new atmosphere in the first place would be the trick. It may take so long as to not matter to the terraformers...

Once you had one, and you could presumably use the mase means to replenish it, you would only need to match the outgassing rate ... which should be less than the early vulcanism rate.

OTOH: if you are resigned to having a non-breathable atmosphere anyway, you could give Mars a greenhouse atmosphere by allowing industrial air pollution perhaps? At least it could warm the place up.

There are a lot of discussions about Mars atmosphere in these forums - have a look.

 

[Menninger]

An alternative explanation could be that Mars lost its atmosphere slowly back then only because it had a magnetic field that partially shielded it from the solar wind. Since Mars no longer has such a magnetic field, it follows that nowadays it could loose its atmosphere relatively quickly. Unfortunately, I can't find a direct answer from a reputable source as to how quickly Mars would loose a rebuilt atmosphere. Maybe we will have such an answer after the MAVEN probe arrives and does its science.

Now a new computer model suggests Mars's magnetic field may have been slowly weakened by four especially large impacts and then snuffed out completely by a fifth and final blow.

That impact created the 2,000-mile-wide (3,300-kilometer-wide) Utopia crater, which dates back roughly 4.1 billion years, said study team member James Roberts of the Johns Hopkins Applied Physics Lab in Maryland.

"It's possible that the four earlier impacts set everything up, and the Utopia crater was the straw that broke camel's back."

http://news.nationalgeographic.com/news/2009/05/090511-mars-asteroid.html

Venus doesn't have a strong magnetic field, meaning that having a molten core doesn't guarantee one.

Regarding being to able to build an atmosphere, there is more than one theoretically possible way you could do it quickly, but using present technology, nuking the ice caps ought do the trick. It might take quite a few nukes though.

Although I would imagine that using super greenhouse gases to sublimate the ice caps would be very time consuming, regardless of their utility in building up the atmosphere, with enough industrial production they should, as you say, allow us to make Mars as hot as we want it to be.

 

[Mordred]

This article in section 2.2.1 covers a bit on Mars CO2 levels
the article also contains some good info on local planets vs habitability.

 

[pmacias]

I can say that you are correct in your understanding that Mars would lose its atmosphere again if we were to build it back up. The mechanisms that caused the loss of its atmosphere in the first place, such as solar wind and low gravity, would still be present on Mars. However, the rate at which Mars would lose its atmosphere would depend on various factors, such as the strength of the solar wind and the amount of gas being outgassed by Mars itself.

In terms of how quickly Mars would lose its atmosphere, it is difficult to determine an exact timeline. As you mentioned, it is likely that it would take millions of years for Mars to lose its atmosphere to a significant extent. This is based on evidence that suggests Mars had a thicker atmosphere in its past, which allowed for liquid water to exist on its surface. The gradual loss of this atmosphere over millions of years is believed to be one of the reasons why Mars is now a cold and dry planet.

However, it is important to note that the rate of atmospheric loss could also be affected by human intervention. If we were to introduce large amounts of gases into Mars' atmosphere in a short period of time, it could potentially accelerate the loss of this atmosphere. This is why careful planning and monitoring would be necessary for any terraforming efforts on Mars.

In terms of your question about importing gases to mimic the outgassing rate of volcanoes, this could potentially be a solution to keep Mars' atmosphere dense indefinitely. However, further research and experimentation would be needed to determine the exact types and amounts of gases that would be necessary to achieve this goal.

In conclusion, while it is possible to build up Mars' atmosphere, it would require careful consideration and planning to ensure that it does not lose its atmosphere again. The rate of atmospheric loss would depend on various factors and could potentially be influenced by human intervention. Further research and experimentation are needed to fully understand and address this challenge in terraforming Mars.