Launching resources from Earth is expensive, in comparison to mining extraterrestrial resources from the moon. Whether lunar materials are more desirable than materials from Near Earth Objects is the subject of many debates. The Solar system theoretically, holds an abundance of minerals, which can be utilized to aid our progression into the Solar System. However, the biggest factor determining the location of the first mining colony in Space is water.

Water Extraction

In 1994, Clementine obtained radar images around the South Pole - Aitken basin and discovered indications of water in the shaded areas of the craters. This water could be used for domestic purposes and also be broken into its component hydrogen and oxygen to provide breathable air. The two elements could also be recombined as fuel for spacecraft or machinery on the base itself. It is estimated that a supply of water from the moon would reduce the cost of a mission to Mars by about 50 percent (Scientific American, 1998).

Present data suggests that water ice is in the form of small crystals, comprising about 0.3 percent to 1 percent of the moon's rocky soil. At such concentrations, a cubic metre of soil would contain as much as 20 litres of water. The key issue is how deeply the water extends into the lunar regolith. The present estimate is based on the depth to which the neutron spectrometer's signal can penetrate--about 50 cm. It has been estimated that the amount of lunar regolith that could have has been produced by all impacts in the past two billion years extends to a depth of about 220 metres. If this is correct, Lunar Prospector's estimate of water ice can be increased by a factor of up to four, to the range of 44 million to 1.3 billion tons (Scientific American, 1998).

According to NASA, an area the size of a football field would yield enough water to provide for the drinking, food preparation, bathing and washing needs of a crew for six persons and generate 100 megawatts of electrical power for a year. Likewise, this same amount could produce enough propellant to transport two crews of four people each, from the Moon to the Earth. Taking an equivalent amount of water along to the moon would be a costly proposition. Currently, it costs about $20,000 to put one kilogram of material into orbit. NASA is conducting research with the goal of reducing that figure by a factor of 10, to only $2,000 per kilogram, but at that rate the cost of providing water to a permanent base--even with recycling--would be trillions of dollars (Scientific American, 1998).

Oxygen

Oxygen is an abundant element in the lunar soil, comprising nearly half of the lunar regolith by mass. Oxygen mined from the moon can play a critical role in space industries. Besides giving us considerable leverage in our development of a space transportation system, lunar oxygen can become one of the lunar community's most important economic exports.

Other Lunar Minerals and Light Elements

Moon dust is a mixture of many different minerals, and nearly all of them contain oxygen in considerable abundance. One of the most common lunar minerals is ilmenite, a mixture of iron, titanium, and oxygen. (Ilmenite also often contains other metals such as magnesium, which we will blithely ignore here.) For this discussion, we'll concentrate on extracting oxygen from ilmenite because there's lots of the stuff available, and because the chemical processes involved in extracting these minerals is not complicated and can be read in detail.

There's an interesting side effect to developing such technology. Today on Earth, most titanium metal is produced from rutile laboriously mined from sands in Florida and Russia. However, if an efficient process is developed for extracting rutile from ilmenite, we might serendipitously have an economic effect on the world's titanium production. On Earth, ilmenite is about fifty times more abundant than rutile; so this research could have a positive effect on the terrestrial production of titanium. Even if that happens, however, we still should be able to deliver titanium to a space borne community at much lower cost than Earth-based producers.

There are a number of methods for extracting minerals from the lunar soil. Here are of them :

• Magnetic separation of free metals
• Thermal extraction of volatiles
• Separating minerals by electrostatic benefiction
• Separating minerals by vibration and floatation

Magnetic Separation of Free Metals

After grinding, streams of material are put through magnetic fields to separate the nickel-iron metal granules from the silicate grains. Repeated cycling through the magnetic field gives highly purified free nickel iron metal. One of several alternative ways is to drop a stream of material onto magnetic drums.

Thermal Extraction of Volatiles

Notably, rocket fuel for the delivery trip to Earth orbit can be produced by separating oxygen and hydrogen gases from the mix, or by electrolysis of water. Alternatively, the hydrogen could be chemically bonded with carbon to produce methane fuel. Tanks for storing frozen volatiles for sending to Earth orbit can be manufactured by some of the free nickel iron metal, by use of a solar oven for melting the nickel iron metal.

Separating Minerals by Electrostatic Means

Electrostatic separation works because minerals have different electrostatic affinities. This process takes advantage of atoms absorbing different amounts of charge depending upon their composition and the resulting deflection by different amounts by an electric field. After grains are sieved by size, they are placed through a separator.

Separating Minerals by Vibration and Floatation

It's possible to separate some minerals by their density, after sieving a source of multi sized grains into equal sizes.

Electrophoresis: Super Mineral Separation In Orbit

"Electrophoresis" for mineral separation can work only in zero gravity. Such a procedure would require a robotic mining platform in lunar orbit or at one of the Earth Moon Lagrange points and is relatively simple with extremely high performance. Electrophoresis works better than electrostatic benefaction but is much slower.

The following minerals can be found in the lunar regolith (numbers in brackets are percentage by weight). Aluminium (7.3), Calcium (8.5), Chromium (0.2), Iron (12.1), Iron (12.1), Magnesium (4.8), Oxygen (40.8), Potassium (0.1), Silicon (0.3) and Titanium (4.5) giving a total percentage by weight of 98.4. Carbon, Nitrogen and Sulphur have also been detected in 200, 100 and 540 parts per million respectively. Lunar soil contains few elements and all are necessary for human colonization. Where can we get other vital nutrients and elements? The answer could be the near Earth objects.

HELIUM-3

Helium-3 is a non-radioactive isotope of helium. It is rare on the Earth, but on the moon it is implanted in the upper meter of the lunar regolith by the solar wind, and has been accumulating for billions of years, thanks to the solar wind. The proposal has been made to mine 3He from the lunar regolith for use in power-generating nuclear fusion reactors on Earth, thus providing a source of power without releasing further quantities of CO2 or other greenhouse gases into the atmosphere. Lunar 3He. Mining may provide non-radioactive thermonuclear fusion power to an energy-starved Earth for thousands of years (Lunar Institute of Technology, 1999). Unlike standard tritium-based fusion reactors, which would produce high-energy neutrons as a by-product, very few neutrons are produced by the 3He reaction. Rather, high-energy protons are generated, but they create no long-term radioactivity in the reaction containment system. A more detailed explanation on the use of 3He can be read in Wittenberg, L.J., Santarius, J.F., and Kulcinski, G.L., 1987, Lunar source of 3He for commercial fusion power, Fusion Technology, v. 10, p. 167-178. However, the technology required for nuclear fusion is very much in its infancy and is far from being realized.

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