# Thermite for metallurgy?

As we all know, a majority of the Martian soil is composed of ferric oxide ($$Fe_2O_3$$), which is also coincidentally the formula for hematite, one of the most common ores of iron.

I think (personally) that it is a fact beyond doubt that iron is absolutely necessary to sustain a civilization anywhere, even on Mars. However, the problem is that most modern metallurgical processes regarding iron require the presence of atmospheric oxygen (ala blast furnaces) or prohibitive amounts of electricity (electric arc furnaces). Both of these are, for obvious reasons, difficult to obtain on Mars. Additionally, they both require carbon, again difficult to obtain on the Red Planet.

Now, enter thermite. Aluminum is a powerful reducing agent, and is used on Earth often to reduce $$Fe_2O_3$$ to molten iron. So, my question is: what if we carry aluminum to Mars and then create a thermite mixture with the soil there, which can then be ignited electrically to produce iron (this requires much less power than an EAF). Thermite can burn in oxygen-less environments, and the aluminum can be reused by electrolyzing the aluminum oxide produced. Additionally, aluminum is a lighter element than iron, and thus can be carried in larger quantities by spaceships.

Is this the best method, or is there something less convoluted and more effective? I am also open to alternatives to iron.

• "aluminum can be reused by electrolyzing the aluminum" - that puts us right back to "prohibitive amounts of electricity" – Mazura Jan 30 at 18:12
• Carbon, in the form of CO2 is relatively common on Mars. You need to look up the work of Robert Zubrin and C Junaedi, and see what you can accomplish with a Sabatier reactor (19th century technology). – pojo-guy Jan 30 at 18:43

Electricity, electsmischity. You don't need to burn stuff or to schlep aluminum around. You have lots of space to build and minimal atmosphere in the way. Even though Mars is 4th in line for the love of Old Sol, Sol has a lot of love to give. You want a solar furnace.

https://cosmosmagazine.com/technology/how-solar-power-towers-generate-electricity-at-night

1. Set up mirrors. I like this circumferential arrangement or you could have a big dish.

2. Focus sun. It gets hot. It cannot get hotter than the sun but it can get as hot as you need for any smelting.

3. It looks awesome because it is awesome.

4. When the invaders come they will think the Martian mining colony is a soft target, with a bunch of miners, scientists and one retired cop with a stun gun. Oh yes, and the Archimedes - a solar forge with a directional mirror...

Side benefit: In a coke furnace, the oxygen split off iron ore goes to support combustion and leaves as CO2. The thermite operation proposed in the OP leaves oxygen bonded to aluminum. The solar forge drives off oxygen as O2. For Martian colonists eager to breathe, the O2 product of a solar forge might be worth more than the iron metal.

• This seems like a nice alternative. What is the exact process of smelting metals with solar furnaces? I mean, what are the raw materials? – Budhaditya Ghosh Jan 31 at 9:00
• Here is a nice overview of iron smelting. science.howstuffworks.com/iron2.htm – Willk Jan 31 at 17:04

aluminum can be reused by electrolyzing the aluminum oxide produced

That requires large amounts of energy, both in form of electricity and heat to smelt the aluminum oxide. Moreover, you need criolite to perform electrolysis on aluminum oxide. I am not sure that is available on Mars.

aluminum is a lighter element than iron, and thus can be carried in larger quantities by spaceships.

Assuming the design of your transport ship is fixed, so it is the load volume. This implies that, transporting aluminum, you actually carry LESS mass, thus you end up having to use more transfers.

All in all, I am not sure this is highly effective or better than simply transporting carbon to Mars, or even using locally available carbon. One, if not the main reason for recycling aluminum is the huge saving which can be achieved by not having to reduce the aluminum oxide.

• Well, cryolite is currently extinct on Earth as well. All cryolite used in modern times is synthetic. Additionally, the power used to electrolyze alumina pales in comparison to what is required in an EAF. – Budhaditya Ghosh Jan 30 at 18:49