Adding CF4 to the Martian Atmosphere (terraforming)

[.Scott]

There are several possible goals related to terraforming Mars. In the short term, Earthling visitors will need to stay indoors or venture out only in pressure suits. But there would be enormous convenience and safety benefits in raising the Martian atmospheric surface pressure from it current feeble average of about 6.1 millibars.

NASA literally wrote the book on human exposure to low atmospheric pressure (SP NASA-3006 - starting on page 6).

There is the Armstrong limit of 63 millibars. That's the vapor pressure of water at body temperature - and exposure to anything less than that results in very immediate problems.

A far more useful goal would be about 250 millibars - where normal blood oxygen levels can barely be maintained with pure oxygen and no pressure suit.

So, while reading about various green-house gases, I looked at CF4, Carbon Tetrafluoride. And my thought is that this could be a major contributor to improving the Martian climate by human standards.

CF4 is a pretty stable molecule, so I would guess that it would tolerate cosmic radiation fairly well and otherwise stick around for quite awhile in the Martian environment.

Compared to O2 and N2, CF4 is a pretty heavy molecule, so even in the weak Martian gravity hole and a solar wind unperturbed by a magnetic field, it would hang on longer. It would also "thin out" quicker as you gained altitude - coming closer to the Earthly rate of about 50% for every 18,000 feet.

It's a very potent green house gas - so things could get toasty.

And, except for the drowning hazard, it is non-toxic.

The surface area of Mars is 144.37 million Km2. For a goal of 250 millibars, you would need the fluorine to contribute about 216 millibars, 200 g/c^2, or 2x10^6 tonnes/Km^2. That works out to 2.89 10^14 metric tons of fluorine. So start mining.

 

[InkTide]

Very interesting idea, though I'd have a couple of concerns. The first would be that such a high proportion of CF₄ would potentially displace breathable O₂ by atmospheric stratification at ground level given how much heavier it would be (molecular weight of ~88 as opposed to ~32 for O₂, ~28 for N₂, and ~44 for CO₂). The second would be that CF₄ interaction with unprotected solar radiation from the lack of a magnetic field could create free fluorine, which even in tiny amounts may react with atmospheric CO₂, CO, O₂, or even H₂O to in turn create some rather nasty byproducts.

 

[.Scott]

It would definitely displace oxygen. The objective would only be to provide atmospheric pressure - not a breathable atmosphere. You would still need to carry oxygen. But you wouldn't need a pressure suit.

Carbonyl fluoride could be a problem, but it is only an irritant and would stay at higher altitudes.

 

[InkTide]

It would definitely displace oxygen. The objective would only be to provide atmospheric pressure - not a breathable atmosphere. You would still need to carry oxygen. But you wouldn't need a pressure suit.

Carbonyl fluoride could be a problem, but it is only an irritant and would stay at higher altitudes.

Ah, I misread your intent then - for pressure it could definitely work.

I was thinking about the potential for surface reactions given fluorine's propensity to violently rip electrons away from other atoms, and it occurred to me that you could potentially in-situ liberate the oxygen in iron oxides all over Mars by exposing the surface minerals to fluorine - I believe the resulting products would be anhydrous iron(III) fluoride and pure oxygen gas, since fluorine is a stronger oxidizer than oxygen. You could use the resulting iron fluoride compound to bind to/filter water (it's extremely hygroscopic and very thermally stable) as both a heat source and a way to store water chemically to prevent evaporation and loss to the Martian atmosphere (followed presumably by loss to the solar wind). Using preexisting projects already used on Mars successfully, you could conceivably displace the oxygen from the second byproduct of the MOXIE device (CO) and yield... well, carbon tetrafluoride for your atmospheric pressure creation projects, plus even more oxygen.

One of the reasons fluorine is so dangerous on Earth is it energetically replaces oxygen compounds that are abundant and normally stable, effectively starting fires that produce pure oxygen gas as a byproduct... which go on to be exactly as reactive as oxygen gas is, plus a lot of energy dumped into the molecules by the fluorine reaction. On the plus side, fluorine compounds tend to be extraordinarily stable as a result... as long as it's not with another halogen or hydrogen (an honorary halogen more than it is an honorary alkali metal).

 

[dlgoff]

CF4, Carbon Tetrafluoride

I wouldn't want any of that stuff around me; here or on Mars.

 

[.Scott]

I wouldn't want any of that stuff around me; here or on Mars.

It would be easier to deal with than a near CO2 vacuum. It may be the best of workable options.

 

[InkTide]

I wouldn't want any of that stuff around me; here or on Mars.

It would be easier to deal with than a near CO2 vacuum. It may be the best of workable options.

Pretty much the only hazards are its reaction with alkali metals and the risk of asphyxiation. The carbon-fluorine bond is literally the strongest single bond in organic chemistry - about the only atmospheric gas that would be more inert would be... well, dinitrogen.