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Asteroid mining refers to the possibility of exploiting raw materials from asteroids and other minor planets, including near-Earth objects. Minerals and volatiles could be mined from an asteroid or spent comet then taken back to Earth or used in space for space-construction materials. Materials that could be mined or extracted include iron, nickel, titanium for construction, 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, using resources gathered whilst on a journey is referred to as in-situ resource utilization.
Based on known terrestrial reserves and growing consumption in developing countries along with excessive exploitation by developed 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. In response, it has been suggested that platinum, cobalt and other valuable elements from asteroids may be mined and sent to Earth for profit, used to build solar-power satellites and space habitats, and water processed from ice to refuel orbiting propellant depots.
In fact, all the gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium, and tungsten mined from Earth's crust, and that are essential for economic and technological progress, came originally from the rain of asteroids that hit Earth after the crust cooled. This is because although asteroids and Earth accreted from the same starting materials, Earth's massive gravity pulled all heavy siderophilic (iron-loving) elements into its core during its molten youth more than four billion years ago.[specify] This left the crust depleted of such valuable elements[specify] until asteroid impacts re-infused the depleted crust with metals. Some flow from core to surface seems to occur, e.g. at the Bushveld Igneous Complex, a famously rich source of platinum-group metals.
In 2006, the Keck Observatory announced that the binary Trojan asteroid 617 Patroclus, 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-situ 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.
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.
The physical human presence may not be needed beyond the near-Earth processing facilities as it would exceed current experience and physiological endurances. One practical solution would be to deploy many autonomous hunter-seeker units which would attach to candidate "Earth-crosser" asteroids and survey companion sources as well as track exact orbits and cycles. It would not be necessary or useful to return large quantities of the materials to Earth, since many metals, such as ferronickel and silicates, are useful for structural components; platinum is useful for catalysing water and methane into component elements, and gold for microprocessor production in a zero gravity environment. Values would be sharply reduced if vast quantities of intrinsically valuable metals were introduced into Earth, instead of being used onsite as core components of microprocessor fabrication that would provide the largest benefit with minimal economic disruption.[better source needed]
From the astrobiological perspective, asteroid prospecting could provide scientific data for the search for extraterrestrial intelligence (SETI). Some astrophysicists have suggested that if advanced extraterrestrial civilizations employed asteroid mining long ago, the hallmarks of these activities might be detectable.
Asteroid selection 
|Earth surface to LEO||8.0 km/s|
|LEO to near-Earth asteroid||5.5 km/s[a]|
|LEO to lunar surface||6.3 km/s|
|LEO to moons of Mars.||8.0 km/s|
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. 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:
- Bring raw asteroidal material to Earth for use.
- Process it on-site to bring back only processed materials, and perhaps produce propellant for the return trip.
- Transport the asteroid to a safe orbit around the Moon, Earth or to the ISS. This can hypothetically allow for most materials to be used and not wasted. (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.[original research?]
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.
Extraction techniques 
Surface mining 
On some types of asteroids, material may be scraped off the surface using a scoop or auger, or for larger pieces, an "active grab." There is strong evidence that many asteroids consist of rubble piles, 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 
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. Exponential growth of factories over many years could refine large amounts of lunar regolith. Since 1980 there has been major progress in miniaturization, nanotechnology, materials science, and additive manufacturing.
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.
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 aerospace entrepreneurs Eric Anderson and Peter Diamandis. Advisers include film director and explorer James Cameron and investors include Google's chief executive Larry Page and its executive chairman Eric Schmidt. 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. The plan has been met with skepticism 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. Planetary Resources admits that, in order to be successful, it will need to develop technologies that bring the cost of space flight down.
Another similar venture, called Deep Space Industries, was started by David Gump, who had founded other space companies. The company hopes to begin prospecting for asteroids suitable for mining by 2015 and by 2016 return asteroid samples to Earth. By 2023 Deep Space Industries plans to begin mining for asteroids.
In September 2012, the NASA Institute for Advanced Concepts (NIAC) announced the Robotic Asteroid Prospector project, which will examine and evaluate the feasibility of asteroid mining in terms of means, methods, and systems.
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. Some 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. Other studies suggest large profit by using solar power. 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.
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. 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, or two to three times the annual production of 2004. 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 says that platinum from a 30-meter long asteroid is worth 25–50 billion USD, an economist remarked that any outside source of precious metals could lower prices sufficiently to possibly doom the venture, by rapidly increasing the available supply of such metals.
Development of an asteroid-orbit manipulation infrastructure could offer an irresistible return on investment, however, astrophysicists Carl Sagan and Steven J. Ostro raised the concern that altering the trajectories of asteroids in nearby interplanetary space could cause a catastrophic collision with Earth. These scientists conclude on the requirement to institute stringent controls on the misuse of orbit-engineering technology.
In fiction 
The 1979 film Alien, directed by Ridley Scott, is about the crew of the Nostromo; a commercially operated spaceship on a return trip to Earth, hauling a refinery and 20 million tons of mineral ore mined from an asteroid.
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
- Timeline of Solar System exploration
- Sample return mission
- Space-based industry
- Space fountain
- In-Situ Resource Utilization
- Space manufacturing
- Near Earth Asteroid Prospector
- Planetary Resources Inc.
- Mining the Sky: Untold Riches from the Asteroids, Comets, and Planets
- Colonization of Ceres
- Colonization of the asteroids
- Manned mission to an asteroid
- Asteroid impact avoidance
- Asteroids in fiction
- ^ This is the typical amount, however much smaller delta-v asteroids exist.
||Constructs such as ibid., loc. cit. and idem are discouraged by Wikipedia's style guide for footnotes, as they are easily broken. Please improve this article by replacing them with named references (quick guide), or an abbreviated title. (May 2013)|
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- 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
- How Asteroids can save mankind
- 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
- Video Moving An Asteroid California Institute of Technology, Workshop Public Lecture Panel, September 2011