Mining

A roadheader digs into a regolith cliff and feeds an automated truck.

Mining is the process of collecting raw materials from the Martian natural resources for further processing. The raw materials extracted from the Martian surface are frozen water, minerals and ore. The thin atmosphere can be exploited for resources by atmospheric mining. Mining is preceded by mineralogical exploration, to identify concentrations of minerals that might be exploited by a mine.

Resources

Mines are built to take advantage of the mineral concentrations created by various planetary processes. If the resources is not sufficiently concentrated, the mining processes are not economical. Mechanisms for mineral concentrations on Mars are mostly hypothetical and the discovery of useful bodies of ore awaits the advent of Martian geologists. Satellite detection has discovered potentially useful resources, such as clays.

Most ores on Earth are created by water, vulcanism, or both. Since Mars has had wide spread flowing water, and volcanoes all over the planet, it is likely that Mars will have valuable ores. (Much more so than Earth's Luna, which didn't have water.)

Technology

Mining is an energy consuming activity. Due to the hostile environment, the digging machines are expected to be automated, or be remote controlled. However, in-situ resources are almost always less expensive than resources imported from Earth.

• Mining on Earth is largely done with an initial phase using explosives to fracture the rock for removal to a processing plant. This might not be the most practical method on Mars, since the production of explosives is fairly energy intensive. Digging and crushing with electrically powered mining equipment might be favored over explosives.
• The production of explosives, such as Ammonium nitrates combined with fuels, would start with the production of ammonia using the Haber-Bosch process. Fuels do not occur naturally on Mars (with the possible exception of Methane Clathrates). So the fuels would also need to be manufactured in processes requiring energy inputs.
• The Haber-Bosch process requires Nitrogen extracted from the Martian atmosphere and hydrogen, extracted from water by electrolysis.

Surface Mining Methods

Strip Mining

When resources are available close to the surface, a strip mine is the most efficient method of extraction. The layers of regolith covering the resource are taken away, and the exposed ore is mined. This method is also called open-pit mining, or regolith harvesting, depending on the depth of the work.

Dust Mining

Martian dust is distributed everywhere by the wind, and it is iron rich. Silicon, sulphur, magnesium, calcium, oxygen and other elements can be extracted from it. It can be used to make low quality bricks with no modification, or better bricks with modest additives or sintering with heat. Any place where the wind deposits dust could be an easy to mine location, which will gradually be refilled. The refill rate may be lower than the extraction rate for larger settlements.

Subsurface Mining Methods

When the natural resource lies far underground, it is more efficient to dig tunnels to access the ore than to remove the overlaying rock and regolith. Since Mars has only about 38% as much gravity as Earth people should be able to extend mines to a depth about 2.6 times as deep as on Earth without the tunnel collapsing from hydrostatic pressure. This should allow the search for valuable minerals to a depth of more than seven kilometers. There are many subsurface mining methods, and they are often used in conjunction with each other.

Drift Mines

Drift mining consists of primarily horizontal tunnels. These are most often dug into a hillside.

Slope Mining

Slope mining uses diagonal tunnels to access ore.

Shaft Mining

Vertical shafts are used in shaft mining. The shaft is often provide with an elevator system and used to access extended horizontal galleries.

Room and Pillar Mining

In this method, large galleries are dug into the ore. Pillars of ore are left at regular intervals to support the ceiling. After all the ore has been removed, these pillars may be removed through retreat mining, leading to the collapse of the chamber. This collapse may lead to surface subsidence.

Longwall Mining

Longwall mining begins with a long horizontal shaft. The roof is held up mechanically by moveable supports. One side of the shaft is mined along its entire length. As this mine progresses, the mechanical supports move forward with the face. The old area of the mine is left unsupported, and allowed to collapse under its own weight, often leading to surface subsidence.

Secondary use for mining galleries

Before and after image of a tunnel settlement.

The artificial caves created by mining can be a valuable side effect of subsurface mining. They can be used to expand the settlement with storage rooms, living rooms, underground greenhouses, gas container for energy storage or for storage of chemicals. They could be used as a Storm shelter during solar storms.

If it is learned that Mars' gravity is detrimental to human health, a centrifuge could increase gravity for the Martians. Placing it underground avoids dust, and radiation. A circular railway a km in diameter is a possibility. See Low gravity for further discussion.

See also

• Atmospheric processing