Challenges of Terraforming Mars: Temperature, Air Pressure, and Radiation

[PAllen]

I think I have a good plausibility argument that Nikitin is right that:

If conditions on Mars surface were made to match Earth surface (temperature, pressure, composition), then density at higher altitudes on Mars would be greater, under reasonable assumptions.

I think we can agree there is no reason for significant composition change in the lower atmospheric levels. Then, I can derive from the ideal gas equations I've given that the only way for density on Mars at higher altitudes to match or be lower than on Earth is for temperature to increase with altitude (or possibly decline much slower than on earth). I think this is implausible. Therefore, if surface conditions match, Mars will have higher density atmosphere than corresponding altitudes on Earth (but still lower than on the ground).

 

[Ryan_m_b]

EDIT: And yeh, while I'm making quite the assumptions, ignoring that the temperature decline on the Martian atmosphere will be quite different than that on earth, I don't see why my assumption is necessarily false, though. And I wouldn't mind at all if people would prove me wrong :D

How about the significantly lower level of energy from the sun (both due to distance and smaller surface area), different surface albedo and different specific heat of the Martian surface (think of how much heat the oceans absorb).

For terraforming this would make a bit of a chicken and egg situation; the atmosphere is going to behave differently because of it's heat. To change the heat you are going to need more greenhouse gases, add oceans and build a biosphere. But to do those (especially the last) will require you to have an atmosphere.

 

[Nikitin]

Well, I don't know about that, but Mars' temperature would remain much more constant than Earth's due to the temperature being much more dependant on insulation of the planet instead of the Sun.. This would result in much less extreme weathers, wouldn't it?

Anyway, the atmosphere would at first be made up of almost exclusively carbondioxide gas. It would take a looong time after creating the atmosphere to actually engineer it to resemble Earth's. This stuff would happen very gradually so probably there will be plenty of time to think about this.

 

[Nikitin]

I think I have a good plausibility argument that Nikitin is right that:

If conditions on Mars surface were made to match Earth surface (temperature, pressure, composition), then density at higher altitudes on Mars would be greater, under reasonable assumptions.

I think we can agree there is no reason for significant composition change in the lower atmospheric levels. Then, I can derive from the ideal gas equations I've given that the only way for density on Mars at higher altitudes to match or be lower than on Earth is for temperature to increase with altitude (or possibly decline much slower than on earth). I think this is implausible. Therefore, if surface conditions match, Mars will have higher density atmosphere than corresponding altitudes on Earth (but still lower than on the ground).

Hmm, yes, what you speak is true. If the temperature would be high throughout the Martian atmosphere then things would be different in the way that the pressure would fall quite slowly as we move up the atmosphere. This would mean that there wouldn't be much need for the extra gases if the temperature could be kept reasonably high throughout the Martian atmosphere..

hmm couldn't this be easily achieved with the use of greenhouse gases?

 

[Drakkith]

I saw earlier in this thread that enough CO2 to thicken the atmosphere sufficiently was already present on Mars as Dry Ice. Is this true?

 

[Ryan_m_b]

I saw earlier in this thread that enough CO2 to thicken the atmosphere sufficiently was already present on Mars as Dry Ice. Is this true?

According to wiki 95% of Mars's atmosphere is CO2 and during winter the poles become covered in dry ice, this sublimes during spring. So the answer seems to be no, there are no extra stocks of dry ice waiting to be sublimed because the dry ice comes from the atmosphere anyway.

 

[Nikitin]

What no! some of the dry ice gets transformed into CO2 during the summer. The vast majority stays frozen.

There is also allot of CO2 in the soil.

If we could heat the planet 5-6 degrees then we'd get a proper atmosphere with proper pressure

 

[Ryan_m_b]

What no! some of the dry ice gets transformed into CO2 during the summer. The vast majority stays frozen.

There is also allot of CO2 in the soil.

If we could heat the planet 5-6 degrees then we'd get a proper atmosphere with proper pressure

Nikitin, as per the PF rules that you agreed to when you signed up it is not enough to simply claim someone is wrong before making your own claim. You need a reference to back you up.

You may very well the right, a quick wiki search did not confirm to me what you have said is true however if you have a citation from a reliable source I would be more than happy to read it.

 

[Nikitin]

http://en.wikipedia.org/wiki/Terraforming_of_Mars see carbondioxide sublimation

 

[Ryan_m_b]

http://en.wikipedia.org/wiki/Terraforming_of_Mars see carbondioxide sublimation

Hmm clicking on the link that that part of the wiki references takes us to this national http://channel.nationalgeographic.c...th-4588/living-on-mars#tab-living-on-mars/10" which itself has no links to published data showing where it got it's information from, it also doesn't say the same thing that the wiki article does. Just googling the 300millibar line from wiki brings up page after page that seem to take the info from wikipedia.

Earlier I did a trawl through various sources to try and find where this claim comes from but found nothing. If you could provide a link to peer-reviewed studies I would be happy to read it, the only research I could find just reiterated the fact that dry ice accumulates in winter and that there is carbon dioxide in Martian soil. I started at http://www.sciencedirect.com/" and searched for various terms such as carbon dioxide/dry ice/mars soil/mars atmosphere etc.

EDIT: I've found one paper that says

The released carbon dioxide will increase the atmospheric pressure and further warm the planet by creating a runaway greenhouse effect. Estimates of the amount of this carbon dioxide vary from 2 to 200 kPa (20–2,000 mbar), but for purposes of planetary ecosynthesis an intermediate amount of 10–40 kPa (100–400 mbar) would be adequate for the early stages.

Frustratingly it has no references for this though. I am also highly sceptical of the veracity of this paper as it chooses atmospheric pressures that the authors hypothesise could exist on Mars and then presents life on Earth that grow on mountains whilst merely paying lip service all the other problems of providing for this life (correct soil, light etc). Like most other terraforming papers this one has no real or concrete science, instead it takes data and suggests "perhaps this is possible". Whilst true without a far better understanding of how to build complex ecosystems statements along the lines of "if we get pressure X we could drop in plant Y and grow Y forests" are no very helpful.

 

[D H]

I have made multiple requests that this thread stay in line with PhysicsForums standards.

That hasn't happened, so thread closed.