Space Mining is where you travel around in space to access the resources of asteroids, moons (e.g.
Deimos) and other planets.
At first sight, this is a silly idea. These bodies are millions of miles away, often are made of similar materials as the Earth, and the Earth is jam-packed full of useful stuff. Even the dirt in your garden is about 15% aluminum; and often has a decent dose of iron to boot.
However, there are several facts that make asteroid mining a desirable idea:
- returning stuff from space to the earth or near to the earth (LEO) is going to be comparatively cheap. (Once you get away from the Earth transportation in zero gravity gets much easier.)
- some asteroids are almost pure metal- between 80-99% iron/nickel (Nickel-Irons). This metal is easily purified further, and can be turned into steel.
- some asteroids are rich in carbon (carbonaceous asteroids); this is useful for making plastics, oil, and many other synthetic materials.
- some asteroids have a lot of ice/water. Steam is a poor, but entirely adequate rocket fuel. See Solar Steamer for how this will open up the solar system for mankind.
- some asteroids are high in platinum group metals (platinum sells for >$400/ounce). Gold and other minerals are also available, but aren't nearly as expensive, so are less worth it...
- returning anything resembling fuel to low earth orbit would be very useful for astronauts and satellites. Currently all fuel is launched from the earth- this pushes the effective price of the fuel up to $1400/lb before you start- and 2/3 of the launch weight of geosynchronous satellites are fuel.
- as an example, the ISS is at a relatively low altitude. This is partly due to the Van Allen Belts which would kill the astronauts at higher altitudes, and also the cost and carrying issues of having enough fuel to go up any higher. Both of these issues go away if sufficient mass can be returned from space; the mass would be used as radiation shield, and some of the mass can be used as propellent.
- some exporting to the earth is likely also; particularly platinum group metals.
But the main use of mining is for people to be able to live permanently in space; and to travel to Mars. The easy access of around 1.4 kw/m^2 of solar energy using just thin bits of aluminum foil to form a solar oven is a powerful tool; and the costs of processing and delivering materials is very likely to be lower in space; long term.