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Author Topic: Why does Mars retain an atmosphere of CO2 but not H2O?  (Read 329 times)

Offline Europan Ocean

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I have learned that Mars has an atmosphere of CO2 that is solid at the Poles and increases seasonally. Mars lost most of it's atmosphere. When this happened it's seas and lakes began to boil off and that became it's atmosphere. But why did Mars retain a little CO2 but only frozen water?


 

Offline VanVinci

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Re: Why does Mars retain an atmosphere of CO2 but not H2O?
« Reply #1 on: 22/08/2016 20:16:31 »
I have learned that Mars has an atmosphere of CO2 that is solid at the Poles and increases seasonally. Mars lost most of it's atmosphere. When this happened it's seas and lakes began to boil off and that became it's atmosphere. But why did Mars retain a little CO2 but only frozen water?

Earth is leaking atmosphere also. Only at a slower rate due to its increased gravity.

The question becomes one of replenishment rate vs loss rate.

With the lion's share of icy comets having already been swept from the inner solar system, maintaining an atmosphere requires that the crust of a planet is only a thin layer above a molten core that is constantly erupting volcanic pimples on the surface.

Someday the Earth will be where Mars is today.

But to your question:

Gravity determines the rate of loss to outer space. When you add the atomic weights for the molecules of CO2 and H2O you find that CO2 is much more massive.

Before you factor in your relative humidity, the air around you is about:
78% N2
21% O2
1% all other gases

CO2 is more massive than the admixture of N2, O2, and water vapor that surrounds you now.

Here's how you can prove it:

Pour about half a cup of Vinegar into a pitcher (or like container) and add a teaspoon of baking soda.

The fizz is the creation of CO2 that will push out the lighter molecules above it.

Lift and slowly tilt the pitcher over a lit candle to decant the CO2 off of the liquid.

You see that the candle is dramatically snuffed by a wave of suffocating CO2.

Thus your answer is that, compared to H2O, CO2 has a much greater Gravitational affinity for the surface.

 

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Re: Why does Mars retain an atmosphere of CO2 but not H2O?
« Reply #1 on: 22/08/2016 20:16:31 »

 

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