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Asteroid mining is the exploitation of 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 used in space for in-situ utilization (e.g. construction materials and rocket propellant) or taken back to Earth. These include gold, iridium, silver, osmium, palladium, platinum, rhenium, rhodium, ruthenium and tungsten for transport back to Earth; iron, cobalt, manganese, molybdenum, nickel, aluminium, and titanium for construction; water and oxygen to sustain astronauts; as well as hydrogen, ammonia, and oxygen for use as rocket propellant. Due to the high costs of current space transportation, extraction techniques still being developed and lingering uncertainties about target selection, terrestrial mining remains the primary means of raw mineral acquisition today. This situation is likely to change in the future as resources on Earth are becoming increasingly scarce and the full potentials of asteroid mining and space exploration are researched in greater detail. However, there is no guarantee asteroid mining will ever attain the volume needed to fully compensate for dwindling terrestrial reserves. == Purpose == Based on known terrestrial reserves, and growing consumption in both developed and developing countries, key elements needed for modern industry and food production could be exhausted on Earth within 50–60 years.〔D. Cohen, ("Earth's natural wealth: an audit" ), ''NewScientist'', 23 May 2007.〕 These include phosphorus, antimony, zinc, tin, lead, indium, silver, gold and copper.〔American Chemical Society, ("Endangered Elements" ), ''ACS website''.〕 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.〔 Although asteroids and Earth accreted from the same starting materials, Earth's relatively stronger gravity pulled all heavy siderophilic (iron-loving) elements into its core during its molten youth more than four billion years ago.〔University of Toronto (2009, October 19).(Geologists Point To Outer Space As Source Of The Earth's Mineral Riches ). ScienceDaily〕 This left the crust depleted of such valuable elements until a rain of asteroid impacts re-infused the depleted crust with metals like gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum, rhenium, rhodium, ruthenium and tungsten (some flow from core to surface does occur, e.g. at the Bushveld Igneous Complex, a famously rich source of platinum-group metals). Today, these metals are mined from Earth's crust, and they are essential for economic and technological progress. Hence, the geologic history of Earth may very well set the stage for a future of asteroid mining. In 2006, the Keck Observatory announced that the binary Jupiter trojan 617 Patroclus, and possibly large numbers of other Jupiter trojans, are likely extinct comets and consist largely of water ice. Similarly, Jupiter-family comets, and possibly near-Earth asteroids that are extinct 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.〔C. Gardner, ("Tobacco and beaver pelts: the sustainable path" ), ''The Space Review'', 18 April 2011.〕 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.〔(Evidence of asteroid mining in our galaxy may lead to the discovery of extraterrestrial civilizations ) smithsonianscience.org〕〔(Asteroid Mining: A Marker for SETI? ) centauri-dreams.org〕〔(Duncan Forgan, Martin Elvis:Extrasolar Asteroid Mining as Forensic Evidence for Extraterrestrial Intelligence )@ arxiv.org, (Retrieved 2011-04-07)〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「asteroid mining」の詳細全文を読む スポンサード リンク
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