In a previous post on colonizing Mars, the question of energy arose. How would we generate energy on Mars? There are more issues here than is immediately apparent, because in thermodynamics we see a clear distinction between heat and work, there is the issue of energy and power density, and there is the issue of portability. The forms we use on earth that we cannot use on Mars include burning fossil fuel (there is none, and no significant oxygen to burn it in), hydro and tidal (because there is no liquid water), geothermal (because we do not know where any fields are, if there are any) or wind (because atmospheric pressure is too low for it to be useful). We can use solar, except the power density during the day is only half that on earth, which means we have to have twice the area of solar cells to get the same effect. This will be fine for electric lighting, or other light uses, but it will not provide a high power density, and you need batteries to store the electric energy. What happens when the batteries need replacement? Nuclear fission and nuclear fusion would be available, always assuming we had developed nuclear fusion technology.
The settlers need continual low-grade heat (because the temperature on Mars is generally below freezing temperature) electric power for working machines, some form of transport fuel, and very high energy density for making things. It is this high-density power that is the problem, and it would seem that nuclear energy, fission or fusion, is required. That in turn requires the settlers have adequate engineers to fix things if they go wrong.
How do we make materials? There are two problems, as illustrated by trying to make iron. The obvious one is to get it hot enough to melt and cast objects (although with 3D printing, you may merely want a powder). But the other is how to get the metallic iron in the first place. One of the problems with Mars is that there has not been a lot of chemical action, as far as we know. At the Meridianum Planum, we know there is some haematite, but generally the iron and most other metals are present in the form of silicates. Silicates are very difficult to break up. Earth has broken them up through chemical weathering, by which carbon dioxide dissolves in water and makes carbonic acid, which in turn very slowly breaks down basaltic type rocks to form silica, and iron and magnesium carbonates. The carbonates have subsequently either been oxidized (basalt contains FeII, but then is oxidized by air to Fe III, and on earth we end up with large deposits of the oxide Fe2O3 that are the major sources of iron ore now, and were deposited from ancient oceans almost three billion years ago when oxygen started to be made by plants. The magnesium has ended up being dissolved and is recovered from sea-water as magnesium sulphate. However, it is not clear whether Mars has had water for long enough to do this. One clue is that when these weathering processes go on, the calcium ends up as limestone. Our admittedly limited survey of Mars has failed to find significant iron or calcium carbonate.
If we were to get some oxides, on earth we reduce those with carbon, but that won’t work on Mars because we are short of carbon. (No coal. We could eventually make charcoal, but it would take some time to grow enough biomass to do that, and of course we have to have the energy to make the charcoal.) We might also want to make glass. Besides having to melt it, we need the raw materials, and they are not readily found, and probably not at the same place. Either we tear silicates to bits, or we have to do a lot of exploration to find the various basics we need. Worse, if we use something like nuclear power to get the energy density, then that has to be somewhere at a distance, and you will need a lot of electric cable. If everything has to be brought from earth, it is going to be a very expensive settlement. In my novel, Red Gold, I had my colonists simply tear apart dust and separate the elements by electromagnetic fields, the same way a mass spectrometer works. That would require extreme energy, and for that I used the two fusion motors that drove the first ships there. That is extreme, and better for fiction, but the point remains, how are settlers going to get raw materials? If the settlers do not have an answer, very soon they will die. This leads to a conclusion: any settlement on Mars will require nuclear fission or fusion to be viable in the longer term. A second conclusion I had for Red Gold is that when making raw materials, the most predominant materials that will be made include iron, aluminium, magnesium and silica. Silica is necessary for glass, in turn needed for glass-houses, while the other metals would be useful for construction, so all is not lost.
Meanwhile, a reminder that Red Gold, and in the UK the first two of my Gaius Claudius Scaevola ebooks are available on promotion over the weekend. (In the US, only the second, Legatus Legionis is on promotion, thanks to an error on my part.)