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Shaun Barrett

Member

From: Cairns, Queensland, Australia

Registered: 2001-12-28

Posts: 2,843

Re: Atmospheric Degeneration

Uh-oh! I was just browsing quickly through the terraforming posts when I realised JoeDaWolf had asked me why I thought a new thicker CO2 martian atmosphere might last a long time.
    Sorry, Joe, I don't always get back to people when I should because of the sheer bulk of posts by new members these days, combined with my slow typing speed!

    If a planet is having trouble holding on to an atmosphere, the air doesn't just all shoot off into space in a flash. You have to consider the individual molecules. In order to escape from Mars, a gas molecule has to reach escape velocity near the top of the atmosphere. If it achieves it near the ground, and even if it happens to be travelling straight up when it reaches that velocity, it is sure to hit another molecule and ricochet off in another direction. You also have to consider the temperature gradient in a column of martian air. Some sections of that column will be at altitudes where the temperature is very low and the gas molecules will be moving slowly. Warmer, faster moving molecules, on their way up from below, will lose energy and rebound in a generally downward direction with reduced velocity.
    The path of a CO2 molecule, from ground-level up to a position where it can finally make its escape out into space, will be a tortuous one involving countless collisions and changes of direction.
    Certainly, there may be a net loss of molecules from Mars over time but it is definitely not a case of "Whoooshh!!", there it goes!

    I got my figure for the longevity of a new thick CO2 atmosphere on a terraformed Mars from [http://mason.gmu.edu/~aweese/bookbag/csi655/]THIS SITE.
    [When you click on it, scroll 2/3rds of the way down the page to the section marked 'Timescale']

    The relevant part states:-

The dominant loss mechanism of CO2 will most likely be the formation of carbonate rocks. Pollack et al. have estimated that the lifetime of a thick CO2 atmosphere in Mars is on the order of 10^7 years without any recycling.

    [For those unfamiliar with it, the '10^7' mentioned is an exponential notation, which means 10 million.]

    So, as you can see, any thick atmosphere we create around Mars will suffer only slight losses over any time span which is meaningful to us as a species. Our problem lies not with the retention of an atmosphere but with its creation in the first place.
                                       

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The word 'aerobics' came about when the gym instructors got together and said: If we're going to charge $10 an hour, we can't call it Jumping Up and Down.   - Rita Rudner

jc314

InActive

From: dallas, tx usa

Registered: 2004-02-10

Posts: 1

Re: Atmospheric Degeneration

I just wonder if Mars suddenly gained an Earth magnatude magnetic field, say someone littered the surface with bus sized bar magnets, or by moving a large electromagnet around the surface like the write head of a planet sized hard drive, would such a field allow the atmosphere to thicken with the gasses present in the solar wind?

Also might the consentration of energy on the poles (assmuing the magnetic field lines up with the existing poles) add a bit of heat and thus contribute to melting the poles?