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Supposing you are trying to colonise planet that has no life what-so-ever but is otherwise an earth analogue.

First thing that I realised is that there would be no oil. So they would need to make bioplastic (assuming they could introduce plants to the inorganic dusty soil).

Then I thought that they could make cement from lime stone, but upon further research I realised that lime-stone is a product of coral and skeletal fragments.

This really got me thinking about how many useful materials are actually the product of living organisms.

Other than metal ores, what useful construction materials exist in the absence of life? What compounds can you synthesise from inorganic rock?

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    $\begingroup$ It's not going to be that close of an Earth-analogue if there's no life at all. The most obvious difference is that it won't have more than miniscule traces of oxygen in the atmosphere. You also wouldn't have iron ore (or at least the commonest sort) as that was created by microbial action. Wikipedia has an overview of ore formation: en.wikipedia.org/wiki/Ore_genesis#Iron It's surprising how much involves some sort of microbial action. $\endgroup$
    – jamesqf
    Commented Feb 16, 2017 at 5:19
  • $\begingroup$ There would be tons of rust... which is great because then you can process that and you have oxygen and iron. Phosphorus would also be easy to find. No worries about methane. $\endgroup$
    – Durakken
    Commented Feb 16, 2017 at 6:36
  • $\begingroup$ Construction aside, radioactive materials should still be easy to come by... and water, and oxygen to breathe $\endgroup$
    – Zxyrra
    Commented Feb 16, 2017 at 6:43
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    $\begingroup$ @Durakken Why do you think there would be lots of rust? Most of the "rusting" on Earth started with the first oxygen-forming life. The consensus so far seems to be that most of the oxygen that formed the "rustlands" originated from deep sources of carbon dioxide and reduction of silicates. It took about 200 million years for the oxygen production to finally saturate the oxygen sinks (like the iron dissolved in the oceans). Without the source of free oxygen, you wouldn't get much rusting (and indeed, asteroids and meteors mostly have pure iron, often alloyed with carbon and nickel, not rust). $\endgroup$
    – Luaan
    Commented Feb 16, 2017 at 11:43
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    $\begingroup$ @Durakken The main iron ore sources we have now are en.wikipedia.org/wiki/Banded_iron_formation - formed as a precipitate of iron oxides formed in a reaction of atmospheric oxygen (dissolved in water) with pure iron (also dissolved in the water). There are other sources of iron ores, which may be oxidised before exposure to the atmosphere (the main that comes to mind is igneous magnetite), but they are tiny deposits compared to the BIFs (and not "really" rust - while still iron oxides, they have very similar density to pure iron, so they don't "flake off"). $\endgroup$
    – Luaan
    Commented Feb 16, 2017 at 13:38

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Silicon

Silicon is everywhere. The rocks are made of it; so is sand, and so would the regolith of your not-at-all Earthlike planet. Silicon bonded with oxygen and metals gets you silicates, which we commonly call "stone" - one of the most common building materials in the world. Silicon bonded with just oxygen makes silicone, and silicone can be used in place of plastics and rubber. Build your structures out of stone with silicone mortar, and you'll be in good shape.

Carbon

Without life, there's still going to be plenty of carbon around, it's just going to be bound up in rocks and carbon dioxide. You're already breaking up rocks to make your silicone, so you can pull carbon out of them at the same time. You can also break up carbon dioxide in the atmosphere to get carbon and oxygen. This deals with your oil shortage quite effectively - we already have the technology to make plastics from atmospheric CO2.

Gypsum

The reason limestone is used to make cement is simply that it's a very common form of calcium carbonate, but it's not the only such form. Gypsum is a common mineral form of calcium sulfate, very soft and easy to mine, and normally accessible near the surface, as it's a sedimentary mineral. You can also extract it from seawater, along with lots of other goodies like sodium.

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Earth was once like that

Do recall that every atom on Earth originate either from the Big Bang (Hydrogen, some Helium) or the fiery fusion furnace that is the center of a star, which then got thrown out into the universe from the massive force of a super nova (everything else).

This was then collected into a swirling ball of hot gas, which then became a molten ball of lava, which - for the most part - it still is, it just so happens the surface has cooled enough so that life as we know it have formed and started using the stuff that was on it.

This means that life is not necessary to create all the things that you need. Life has for instance not created the Calcium that you find in limestone deposits, it was already there. Life just accumulated it for you.

You can synthesize "everything", with enough energy

I put "everything" in quotes because there are some complex substances that we humans have not yet perfected creating. But for all the simple stuff, like Calcium Carbonate and Calcium Silicates that you need for making cement, you can synthesize, as long as you just have an abundance of energy.

So you bring your reactor, either plain old fission reactor running on Uranium or Thorium or discarded Plutonium, or a handy little fusion ditto like a Polywell running on Boron and Hydrogen. These are the first thing you then mine: fuel for your reactor.

Next up you want to sustain yourself. For that you need water, air and fertilizer. Using the energy from your handy reactor you reduce minerals to extract Oxygen, Nitrogen, Hydrogen, Phosphorous and Carbon Dioxide. From this you start your hydroponics. Then, using the plant matter from these, and the load of useful soil bacteria you brought along, you can start making real soil.

In the mean time you are also busy extracting all sorts of primary materials, Silicates, Calcium, Iron, Aluminium and so on, to be used for construction materials.

I am not saying this will be easy or efficient, but if you just hand-wave away the difficulties in producing energy — by for instance assuming that fusion is viable and works as well as we hope it will — then you will have all the starting material you need to get going.

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There's a good reason a lot of useful materials are formed from life - life collects energy and stores it in its biomass, which means that energy can be utilized later. As a result, it is unlikely that you would find a substitute for oil on a lifeless world, although there are some unconfirmed theories that oil generation may be possible without life.

Tectonically active planets may have usable geothermal energy sources that can be used for powering fuel cells, although it probably wouldn't be a useful export, since if you're in space already it's much more practical to generate energy from sunlight than go all the way down into the gravity well of a planet and carry fuel cells away from it. It could be useful for powering other operations on the planet though.

The main useful materials on rocky planets are raw materials like metals and minerals, and radioactive elements for nuclear fuel. Gas giants have an abundance of hydrogen and helium, which would be be important for fusion reactors or any number of future technologies. Helium may also be mined from rocky planets if scooping it from gas giants is impractical for some reason.

It is worth noting that for metals at least, asteroid mining would be more practical than planet mining since you don't have a huge gravity well to lug all that mass away from. However, asteroids aren't that big, and if you have an abundance of energy and a shortage of matter for big projects, planetary mining may be worthwhile.

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  • $\begingroup$ We know that oil can form without life. The debate is whether any of the deposits we're mining is abiogenic or not - and the conclusion so far on that seems to be "a few might be consistent with abiogenic origin, but also with biogenic". But it certainly wouldn't be plentiful, unless we're talking about a world like Titan; where the missing part wouldn't be the fuel, but the oxidizer. Indeed, missing oxidizer would IMO be by far the biggest issue in general - it's something people take for granted on Earth, but it would make any combustion very expensive without "free" atmospheric oxygen. $\endgroup$
    – Luaan
    Commented Feb 16, 2017 at 11:38
  • $\begingroup$ When I said that there was no oil, I was thinking about large scale plastic/rubber production, not as a fossil fuel. I was thinking that we'd probably need fusion power before we could ever colonise another star system. $\endgroup$
    – Lorry Laurence mcLarry
    Commented Feb 16, 2017 at 12:28
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A ideal sized planet with an insulating atmosphere, liquid water and in the Goldilocks orbiting zone is about as ideal for terraforming as you can really hope to find (earth analogue goes a long way). It will take time and effort, but you've already gone to the effort of getting there.

Terraforming is a long term investment a you might get a spare planet out of it. You also have a planet where you can dump all the waste you like. Whats the worst that could happen? A ecosystem emerging?

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Natural Helium is most commonly the result of radioactive decay of several naturally occurring radioactive elements like uranium and thorium. Yes, it is possible that a future society could produce the gas via fusion reactors, but today, helium is a rather expensive and rare gas.

Additionally, rarer forms of Helium like the isotope Helium-3 can be found on "lifeless rocks" and could actually be valuable enough today to warrant mining it on the Moon. It is potentially extremely valuable in energy creation as nuclear fuel.

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