7

In this answer to the question "What would the full hypothetical Mars terraforming roadmap look like ?" there's a link to the article "Zubrin on Terraforming Mars" in Universe Today,
From an interview with Robert Zubrin in that article:

RZ: If one considers the problem of terraforming Mars from the point of view of current technology, the scenario looks like this:

  1. A century to settle Mars and create a substantial local industrial capability and population.
  2. A half century producing fluorocarbon gases (like CF4) to warm the planet by ~10 C.

(Emphasis by me)

Part of the main question is: did he sufficiently take into account the extremely large amount of rock that needs to be excavated and processed to extract the required amount of Fluorine ?

The MSL rover Curiosity detected fluorine containing minerals in Gale crater.

RonJohn
  • 1,102
  • 6
  • 17
Cornelis
  • 7,535
  • 2
  • 26
  • 77

1 Answers1

5

I dug out The Case For Mars (1997) and while it gives some very basic outlines of this, it does not go into any great detail. From Chapter 9:

The industrial effort associated with such a power level would be substantial, producing about a trainload of refined material every day and requiring the support of several thousand workers on the Martian surface. Power levels of about 5000 MWe might be needed, which is about as much power as is required today by a large American city such as Chicago. A total project budget of several hundred billion dollars might well be required. Nevertheless, all things considered, such an operation is hardly likely to be beyond the capabilities of the mid-twenty-fist century.

These calculations in the book are based on producing enough CFCs (probably CF4) to raise the global temperature by around 10K, which he calculates as 0.04 microbar of CFCs, needing about 880 tonnes/hour for twenty years, and an ongoing production rate of about a fifth of that to maintain it once it's built up.

He does not specifically discuss the mining infrastructure needed to get the fluorine, but as it's talking about thousands of workers and city-scale power requirements, it's clear he's aware of how substantial a project it would be.

Andrew is gone
  • 7,801
  • 30
  • 41
  • 1
    Query: When the authors mentions years, is that Earth years or Martian years? There's a big difference. – Fred May 31 '21 at 16:07
  • @Fred Good question - he doesn't say. There may be a "all years in this book mean X years" note somewhere but not in that chapter. – Andrew is gone May 31 '21 at 16:11
  • Thank you for digging out "The Case For Mars" ! What I'm particularly interested in is how 0.04 microbar CF4 can raise the temperature by 10 K. Are there specific formulas he uses to calculate that raise in temperature ? – Cornelis May 31 '21 at 17:40
  • 2
    @Fred aha, I've just noticed the previous table in this chapter explicitly says "Earth years"; I think we can probably guess that is the time units being used throughout. – Andrew is gone May 31 '21 at 18:17
  • 1
    @Cornelis The model he's using is described in the chapter, but the specific calculation for CFCs isn't given (it's dealt with in about a page, as one of several options). – Andrew is gone May 31 '21 at 18:20
  • 2
    "such an operation is hardly likely to be beyond the capabilities of the mid-twenty-fist century." I just hate handwavium. – RonJohn Jun 01 '21 at 04:57
  • @Andrew: Thanks. I thought that might have been the situation. – Fred Jun 01 '21 at 05:29
  • 2
    @Cornelis: CF4 is an aggressive greenhouse gas (much more aggressive than CO2). But to get reasonable estimates of warming you need a proper atmospheric model complete with lapse rates for both temperature & pressure: simple-minded single-layer models don't work, at all. Given known lapse rates it is possible to hand-crank such a calculation as Arrhenius did to get quantatively-OK estimates, or to run a very trivialised computer model. That might be good enough on Mars as there's not much water in the atmosphere. –  Jun 01 '21 at 09:36
  • @tfb So how do you think Zubrin got the value of 10⁰ C warming up with 0.04 microbar CF4 ? – Cornelis Jun 01 '21 at 12:13
  • 1
    @Cornelis: I hope he ran or hand-cranked a simple climate model: the only way to actually know would be to ask him or chase down his references. There's lots of work on the climate of Mars and it would be relatively easy to plug in some increase in the amount of CF4 into a model to see what you get. A GCM might even give you a good answer but some simple one-dimensional model would probably be good enough. –  Jun 01 '21 at 13:50
  • @Andrew By rhe way, fluorocarbon gases are not CFC's. – Cornelis Jun 02 '21 at 08:28
  • @tfb I'm particularly interested what a heavy fluorocarbon gas could bring about in a low lying and deep crater. There the production could take place and the heavy gases would slowly spread out over the rim. Couldn't that make a local climate model still more simple, simple enough to show it with all the necessary formulas ? – Cornelis Jun 02 '21 at 08:43
  • @Cornelis: I assume the mixing time of the atmosphere is fairly short but, yes, in the meantime you could perhaps treat this as a spectacularly expensive and inefficient greenhouse. –  Jun 02 '21 at 08:58
  • @tfb For instance C4F10 is 5 times heavier than CO2, wouldn't that keep it inside the crater for some time ? – Cornelis Jun 02 '21 at 09:03
  • 1
    @Cornelis: I don't know what the mixing time for the Martian atmosphere is. On calm days you might be OK. If it ever gets windy in the crater then ... not. –  Jun 02 '21 at 10:43