Aluminum oxides are abundant on Mars as on Earth. Most aluminum is incorporated into alumina-silicate minerals, such as feldspar ((KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8). Erosion, either by wind or water, can separate out the alumina, possibly as fine dusts that would have turned into compact silts and clays over time. This might be a useful source of aluminum ore.
Aluminum is widely used in places where strong light materials are needed. On Mars, iron and steel weigh almost exactly the same as aluminum does on Earth, and could thus serve in many of those situations.
Production of aluminum
For in-situ production, a source of aluminum ore such as alumina deposits would be very helpful in reducing the processing requirements.
Traditionally aluminum requires high electric power to reduce it from its oxides using electrolysis. Work has been going on for several decades on the carbothermic process, which uses carbon and thermal power, to try to make it as economical on Earth as electrolytic reduction. If thermal power is cheaper than electric power on Mars relative to Earth, due for example to being more suitable for an import-minimizing economy, the carbothermic process will be relatively more attractive. Of course carbon itseld would need to be produced on Mars, which has no handy coal reserves as a carbon source. Methane might be a practical alternative, if methane clathrates, for example, are found on Mars.
Alcoa has announced in 2018 the production of aluminum using a new electrolytic process that does not produce CO2 or require carbon anodes. This might be applicable on Mars.
Once it has been produced, aluminum is relatively easy to recycle and less prone to corrosion than iron and steel.
The embodied energy of aluminum is 155-220 MJ/kg. (To be confirmed, may include significant recycled aluminum at the lower value).
Greenhouse Gases Produced by Aluminum Smelting
On Earth, molten aluminum must be kept away from oxygen or it will oxidize. They used to use a super greenhouse gas sulphur hexafluoride (F6S) over pools of molten aluminum ore. Sulphur hexafluoride is extremely chemically inert, even at high temperatures. However, this is a super greenhouse gas, and current regulations require that great care be made to prevent it from leaking into the atmosphere, or require the use other, more expensive, chemicals. Either of these solutions, increase the cost of of the industrial process.
On Mars, the cheaper form of aluminum smelting can be used, because leaking super greenhouse gases into the atmosphere is something that people want. This is typical for other industries. Where ever super greenhouse gases are regulated, (to prevent warming the Earth), on Mars this regulation is not needed.
- Electrical conductors will be a significant use case for aluminum. In particular if copper is difficult to find on Mars.
- Aluminum is a good material for extrusions used in construction materials such as window and door frames.
- Mobile equipment may benefit from aluminum alloy parts.
- Lithium - aluminum alloys are very strong and light, and are used in the space industry.
- Batteries using aluminum exist and have high energy density, but for the moment are used as single use applications as they are not easily rechargeable.
- Transparent aluminum (Aluminium oxynitride, (AlN)x·(Al2O3)1−x,) can serve as super strong windows. The materials is a transparent ceramic rather than a metal. However, the productions cost are likely to be high. A competing material might be alumina (Al2O3), again an expensive material to produce as a transparent ceramic.
- Aluminum cans are a common aluminum product.