Sci-Fi World-building: Mars the farm planet?

[Michael Thayne]

Premise: Your sci-fi setting has powerful, efficient "torch drives" (like the Epstein Drive from The Expanse), which make getting into orbit from a planet's surface cheap.

Premise: In your sci-fi setting, Mars is being terraformed. Never mind the original motive for this—maybe in the 22nd century China came under the sway of a dictator who was obsessed with the idea for no rational reason. However, the terraforming project is a centuries-long affair. Currently, the atmosphere is reasonably thick and the surface is reasonably warm, but where the atmosphere has way too little oxygen and way too much CO2 for unassisted humans.

I've seen both of these premises independently in fiction, but taken together they seem to support a surprising conclusion: Mars could be a major exporter of agricultural products, most obviously food but also potentially lumber, biofuels, and so on. This doesn't require Mars to produce nearly as much food as Earth. Producing food on Mars just needs to be easier than getting human colonists to move there. And Mars producing say 5% of Earth's food is plenty in terms of justifying the existence of a decent-sized civilian space fleet.

Thoughts? Are there any big scientific problems with this setup once you accept the One Big Lie of torch drives?

[Fred Brackin]

Originally Posted by Michael Thayne

Thoughts? Are there any big scientific problems with this setup once you accept the One Big Lie of torch drives?

Sunlight. You need to increase sunlight by about 250%. You may ayhve already done this in your warming-up program. Probably with Big mirrors.

Next is probably hydrogen. Mars may be deficient in this and you'll need to import it.

[Anders]

Water. You'll need to crash a few ice meteors into the planet. (Yeah, there's water, but there doesn't seem to be very much).

[whswhs]

Originally Posted by Anders

Water. You'll need to crash a few ice meteors into the planet. (Yeah, there's water, but there doesn't seem to be very much).

In The Moon Is a Harsh Mistress, Heinlein had Luna exporting food to Earth. But since Luna had only scattered pockets of ice, its own water supply was getting depleted, and famine was only a few years away. They ended up arranging to have water shipped up from Earth to Luna, which must have considerably raised the cost of that grain.

If I were going to drop comets or other icy bodies onto Mars, I'd aim for terrain that was going to become large bodies of water anyway. The maps in GURPS Mars will suggest some options.

[whswhs]

Originally Posted by Michael Thayne

Thoughts? Are there any big scientific problems with this setup once you accept the One Big Lie of torch drives?

Seems like a classic case of comparative advantage. If Martian agricultural products cost twice as much as Terran, but Martian manufactures cost ten times as much, Mars can get rich shipping food to Earth.

[Johnny1A.2]

Originally Posted by whswhs

Seems like a classic case of comparative advantage. If Martian agricultural products cost twice as much as Terran, but Martian manufactures cost ten times as much, Mars can get rich shipping food to Earth.

I don't follow. If we're assuming Terra is the market, what's the motivation for Terrans to buy Martian produce when it's twice as expensive as locally grown? The only way that would make sense is if there's enough Martian demand that Terran farmers can make more money manufacturing, which doesn't make sense either.

What might be a market for Martian foodstuffs is whatever human presence exists in the asteroids or elsewhere in space. Even with a torch drive, it's still going to be cheaper to launch from Mars than Earth, after all.

Also, if there was a luxury cachet attached to Martian food, the double-cost might then be tolerable. The cachet could be something real (Martian grown grapes turn out to make awesome wine, or Martian-grown coffee turns out to have unique flavor), or purely hype, as long as people were willing to pay for it.

[Johnny1A.2]

Originally Posted by Anders

Water. You'll need to crash a few ice meteors into the planet. (Yeah, there's water, but there doesn't seem to be very much).

Actually, that's not entirely clear. We don't really know just how much water there is, because what there is most likely in the form of deep ice. Some theoretical models of planetary formation suggest that Mars ought to have a lot of native water, but of course that's theory.

But it's entirely possible that Mars actually has quite a lot of water. We won't know until we go and have a thorough look.

[ericthered]

Martian seasons are longer than earth's, and that's going to matter for at least some of your crops. You can genetically engineer around, this, and you can probably breed around this, but it takes time and is something you have to do.

You'll want to decide how "Wet" this terraformed mars is. You could have covered half of mars with oceans, or the whole thing could be slowly working towards an entire planet of Gobi desert.

[Prince Charon]

One advantage to exporting anything from Mars is that the gravity is lower than Earths, so even with the super-cheap torch drives, liftoff from Mars will still be much cheaper than liftoff from Earth.

[whswhs]

Originally Posted by Johnny1A.2

I don't follow. If we're assuming Terra is the market, what's the motivation for Terrans to buy Martian produce when it's twice as expensive as locally grown? The only way that would make sense is if there's enough Martian demand that Terran farmers can make more money manufacturing, which doesn't make sense either.

You're assuming that "cost" means "price." I'm using the word in a more technical sense: cost = what the Martians have to give up to grow the wheat.

On Earth, let us say, we can produce wheat or motors. So we can suppose that one average motor uses as much productive capacity as some weight of wheat. Then producing 10 motors means giving up 10 weights of wheat, and vice versa.

On Mars, the same productive capacity produces 5 weights of wheat or 1 motor. So producing 10 motors means giving up 50 weights of wheat; producing 10 weights of wheat means giving up 2 motors.

So it's a good deal for the Martians not to produce their own motors. If they cut down motor production by 1, they can grow 5 more weights of wheat, and ship 4 of them them to Earth. On Earth, those 4 weights of wheat swap even for 4 motors. If half of those go back to Mars, Mars has gotten 2 imported motors in place of the one it didn't manufacture; and Earth has manufactured 4 motors and ended up with 4 wheat AND two motors. The net outcome makes both planets better off.

David Ricardo demonstrated this about two centuries ago, as a general result; it's one of the core theorems of classical economics, and one that remains valid.

You don't need to be better at producing anything; you just need to be less worse at some things than at others to have a viable economic role.