Asteroid mining

433 Eros is a stony asteroid in a near-Earth orbit

Asteroid mining refers to the possibility of exploiting raw materials from asteroids and other minor planets, including near-Earth objects.^[1] Minerals and volatiles could be mined from an asteroid or spent comet to provide space-construction materials (e.g., iron, nickel, titanium), to extract water and oxygen to sustain the lives of prospector-astronauts on site, as well as hydrogen and oxygen for use as rocket fuel. In space exploration, these activities are referred to as in-situ resource utilization.

Purpose

Based on known terrestrial reserves and growing consumption in developing countries, there is speculation that key elements needed for modern industry, including antimony, zinc, tin, silver, lead, indium, gold, and copper, could be exhausted on Earth within 50–60 years.^[2] In response, it has been suggested that platinum, cobalt and other valuable elements from asteroids may be mined and sent to Earth for profit, and water mined from ice could be used for orbiting propellant depots,^[3][4][5] solar-power satellites, and space habitats.^[6][7]

In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium, and tungsten mined from the Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit the Earth after the crust cooled.^[8][9][10] This is because, while asteroids and the Earth congealed from the same starting materials, Earth's massive gravity pulled all such heavy siderophilic (iron-loving) elements into the planet's core during its molten youth more than four billion years ago.^[11] This left the crust depleted of such valuable elements^[12] until asteroid impacts re-infused the depleted crust with metals.

In 2006, the Keck Observatory announced that the binary Trojan asteroid 617 Patroclus,^[13] and possibly large numbers of other Jupiter Trojan asteroids, are likely extinct comets and consist largely of water ice. Similarly, Jupiter-family comets, and possibly near-Earth asteroids that are defunct comets, might also economically provide water. The process of in-site resource utilization—using materials native to space for propellant, tankage, radiation shielding, and other high-mass components of space infrastructure—could lead to radical reductions in its cost.^[1]

Ice would satisfy one of two necessary conditions to enable "human expansion into the Solar System" (the ultimate goal for human space flight proposed by the 2009 "Augustine Commission" Review of United States Human Space Flight Plans Committee): physical sustainability and economic sustainability.

From the astrobiological perspective, asteroid prospecting could provide scientific data for the search of extraterrestrial intelligence (SETI). Some astrophysicists have suggested that if intelligent and more advanced civilizations came to our Solar System, there is some probability that these civilizations turned to asteroid mining long ago. If so, the hallmarks of their mining activities might be detectable from Earth.^[14]

Asteroid selection

An important factor to consider in target selection is orbital economics, in particular the change in velocity (Δv) and travel time to and from the target. More of the extracted native material must be expended as propellant in higher Δv trajectories, thus less returned as payload. Direct Hohmann trajectories are faster than Hohmann trajectories assisted by planetary and/or lunar flybys, which in turn are faster than those of the Interplanetary Transport Network, but the latter have lower Δv than the former.

Near-Earth asteroids are considered likely candidates for early mining activity. Their low Δv location makes them suitable for use in extracting construction materials for near-Earth space-based facilities, greatly reducing the economic cost of transporting supplies into Earth orbit.

The table at right shows a comparison of Δv requirements for various missions. In terms of propulsion energy requirements, a mission to a near-Earth asteroid compares favorably to alternative mining missions.

An example of a potential target for an early asteroid mining expedition is 4660 Nereus.^{[citation needed]} This body has a very low Δv compared to lifting materials from the surface of the Moon. However it would require a much longer round-trip to return the material.

Mining considerations

There are three options for mining:

1. Bring raw asteroidal material to Earth for use.
2. Process it on-site to bring back only processed materials, and perhaps produce propellant for the return trip.
3. Transport the asteroid to a safe orbit around the Moon, Earth or to the ISS.^[5] This can hypothetically allow for most materials to be used and not wasted.^[7] (see Methods for asteroid retrieval or catching)

Processing in situ for the purpose of extracting high-value minerals will reduce the energy requirements for transporting the materials, although the processing facilities must first be transported to the mining site.

Mining operations require special equipment to handle the extraction and processing of ore in outer space. The machinery will need to be anchored to the body, but once in place, the ore can be moved about more readily due to the lack of gravity. Docking with an asteroid can be performed using a harpoon-like process, where a projectile penetrates the surface to serve as an anchor then an attached cable is used to winch the vehicle to the surface, if the asteroid is rigid enough for a harpoon to be effective.

Due to the distance from Earth to an asteroid selected for mining, the round-trip time for communications will be several minutes or more, except during occasional close approaches to Earth by near-Earth asteroids. Thus any mining equipment will either need to be highly automated, or a human presence will be needed nearby. Humans would also be useful for troubleshooting problems and for maintaining the equipment. On the other hand, multi-minute communications delays have not prevented the success of robotic exploration of Mars, and automated systems would be much less expensive to build and deploy.^[15]

Material extraction

Artist's concept of asteroid mining.

Strip mining

Material is successively scraped off the surface in a process comparable to strip mining. There is strong evidence that many asteroids consist of rubble piles,^[16] making this approach possible.

Shaft mining

A mine can be dug into the asteroid, and the material extracted through the shaft. This requires precise knowledge to engineer accuracy of astro-location under the surface regolith and a transportation system to carry the desired ore to the processing facility.

Magnetic rakes

Asteroids with a high metal content may be covered in loose grains that can be gathered by means of a magnet.^[17]

Heating

For volatile materials in extinct comets, heat can be used to melt and vaporize the matrix.^[18]

Self-replicating machines

A 1980 NASA study entitled Advanced Automation for Space Missions proposed a complex automated factory on the Moon that would work over several years to build a copy of itself.^[19] Exponential growth of factories over many years could refine large amounts of lunar regolith. Since 1980 we have seen several decades of technological progress in miniaturization, nanotechnology, materials science, and additive manufacturing (or 3D printing).

The power of self-replication is compelling. For example, a 1 kg solar-powered self-replicating machine that takes one month to make a copy of itself would, after just two and a half years (30 doublings), refine over one billion kilograms of asteroidal material without any human intervention. Ten months later you would have one trillion kg of whatever metal(s) are used to make the devices, which could then be "harvested" at any time. No large mass of equipment need be delivered to the asteroid; in effect, only the information that went into designing the device plus the 1 kg device itself.

Economics

Currently, the quality of the ore and the consequent cost and mass of equipment required to extract it are unknown and can only be speculated. Economic analyses indicate that the cost of returning asteroidal materials to Earth far outweighs their market value, and that asteroid mining will not attract private investment at current commodity prices and space transportation costs.^[20][21] However, potential markets for materials can be identified and profit generated if extraction cost is brought down. For example, the delivery of multiple tonnes of water to low Earth orbit for rocket fuel preparation for space tourism could generate a significant profit.^[22]

In 1997 it was speculated that a relatively small metallic asteroid with a diameter of 1.6 km (0.99 mi) contains more than $ 20 trillion USD worth of industrial and precious metals.^[4][23] A comparatively small M-type asteroid with a mean diameter of 1 kilometre (0.62 mi) could contain more than two billion metric tons of iron–nickel ore,^[24] or two to three times the annual production of 2004.^[25] The asteroid 16 Psyche is believed to contain 1.7×10¹⁹ kg of nickel–iron, which could supply the world production requirement for several million years. A small portion of the extracted material would also be precious metals.

Although Planetary Resources say that platinum from 30-meter long asteroid is worth 25-50 billion USD,^[26] an economist remarked that any outside source of precious metals could lower prices sufficiently to possibly doom the venture.^[27]

Proposed mining projects

On April 24, 2012 a plan was announced by billionaire entrepreneurs to mine asteroids for their resources. The company is called Planetary Resources and its founders include film director and explorer James Cameron as well as Google's chief executive Larry Page and its executive chairman Eric Schmidt.^[1][28] They also plan to create a fuel depot in space by 2020 by using water from asteroids, which could be broken down in space to liquid oxygen and liquid hydrogen for rocket fuel. From there, it could be shipped to Earth orbit for refueling commercial satellites or spacecraft.^[1]

The plan has been met with scepticism by some scientists who do not see it as cost-effective, even though platinum and gold are worth nearly £35 per gram ($1,600 per ounce). An upcoming NASA mission (OSIRIS-REx) to return just 60g (two ounces) of material from an asteroid to Earth will cost about $1 billion USD.^[1] Planetary Resources admit that, in order to be successful, they will need to develop technologies that bring the cost of space flight down.

In fiction

The first mention of asteroid mining in science fiction is apparently Garrett P. Serviss' story Edison's Conquest of Mars, New York Evening Journal, 1898.^[29][30]

Gallery

• 

  Artist's concept from the 1970s of asteroid mining

• 

  Artist's concept of an asteroid mining vehicle as seen in 1984

• 

  Artist's concept of an asteroid moved by a space tether

• 

  A future space telescope designed by Planetary Resources company to find asteroids

See also

• Space exploration
• Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets
• Space manufacturing
• Space-based industry
• In-Situ Resource Utilization
• Near Earth Asteroid Prospector
• Planetary Resources Inc.
• Colonization of the asteroids
• Colonization of Ceres
• Asteroids in fiction

Notes

References

Publications

• Space Enterprise: Beyond NASA / David Gump (1990) ISBN 0-275-93314-8.
• Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets / John S. Lewis (1998) ISBN 0-201-47959-1
• Ricky Lee: Law and Regulation of Commercial Mining of Minerals in Outer Space. Springer, Dordrecht 2012, ISBN 978-94-007-2038-1

External links

Find more about Asteroid mining on Wikipedia's sister projects:
	Images and media from Commons
	Learning resources from Wikiversity
	Textbooks from Wikibooks

Text

• The Technical and Economic Feasibility of Mining the Near-Earth Asteroids, M. J. Sonter.
• The Future of Space Mining
• The Plan to Bring an Asteroid to Earth

Video

• Video Beyond Earth - NEO Destinations NewSpace Conference of the Space Frontier Foundation, Aug 7, 2011
• Video Moon, Mars, Asteroids - Where to Go First for Resources? Space manufacturing Conference of the Space Studies Institute, October 2010