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20 SEG NEWSLETTER No 65 • APRIL 2006Feasibility of Asteroid MiningMichael W. Busch † , Division of Geology and Planetary Science, California Institute of TechnologyMC 150-21, Pasadena, California 91125SHORT ARTICLESAbout 2% of meteorites observed to fall toEarth are near-pure nickel-iron, implyingNiFe objects somewhere in the solar system.Over the last decade, radar observationsof asteroids have located four suchobjects (Table 1). The NiFe asteroids arethe largest accessible reserve of platinumgroupelements (PGEs) in the solar system.Nickel-iron meteorites contain about 60ppm of PGEs on average, uniformly distributedin the NiFe matrix. The richestcontain over 150 ppm (Table 2).Carbonyl processing, similar to operationsat the International Nickel plant atSudbury, Ontario, is the best method ofextracting PGEs from an asteroid on anindustrial scale (Lewis and Lewis, 1987).Since the PGEs are uniformly distributed,the entire mass must be ground andreacted with CO to form carbonyls, whichare then decomposed according to species.This process requires about 40 Mw of solarthermal and electrical power to process3.25 million metric tonnes (t)/year. Othermethods, such as thermal separation, arefar more energy-intensive.The largest contributor to the cost ofany space mission is the total massneeded in Earth orbit, since launch costsare currently about US$15,000/kg (allcosts are in January 2006 U.S. dollars).Therefore, the target should require thesmallest possible velocity change fromEarth orbit, to decrease the mass of fuelthat must be brought up from Earth. Thetarget should also have the highest possiblesolar flux, to minimize the mass ofthe power plant. Asteroid 1950 DA is thebest known target.If 1950 DA has an average concentrationof PGEs, a total system mass ofabout 190 t in Earth orbit is sufficient toprocess 3.25 million t/yr and return theresulting 180 t/yr of metal from the asteroidto the Earth’s surface. The carbonylprocess requires a large number of moving† E-mail: busch@caltech.eduTABLE 1. Known Nickel-Iron AsteroidsTABLE 2. Precious Metals in Nickel-IronMeteoritesConcentrationElement Average HighestPlatinum 20 ppm 30 ppmPalladium 10 ppm 20 ppmRuthenium 10 ppm 30 ppmGold 5 ppm 20 ppmIridium 5 ppm 20 ppmOsmium 3 ppm 35 ppmAverages over nickel-iron meteoritesfrom Krinov, 1960; the highest PGE contentsare from the type IIA irons(Goldberg et al. 1951, Crocket 1972)parts, however, so a crew is desirable tomaintain the equipment. A crew of four tosix in a closed-cycle life support systemadds 60 t to the Earth-orbit mass. The costof such a 250-t spacecraft would likely bein the vicinity of $5 billion, including thecost of assembly before launch. For comparison,the initial cost of an Earth-basedplatinum-palladium mine producing 22t/yr of PGE is about $1 billion (ImpalaPlatinum, 2005).The revenue from selling 180 t/yr ofPGEs in the ratios present in nickel-irondepends on Earth demand. Using priceand production data for the last decade,assuming linear price elasticity andadjusting for inflation, I estimate the revenueat $1.9 to $2.8 billion/yr, with theprice of PGEs decreasing by up to 35%.The range represents uncertainty in theEarth production and price elasticity ofeach species. For example, I have notincluded the effects of a decrease in PGEprices on Earth-based mining.Because an asteroid mining missionmust be able to operate almost independentlyof Earth, operating costs are muchsmaller than the uncertainty in my revenueestimates. Revenue of $1.9billion/yr is sufficient to repay a $5 billioninitial cost within three years,Asteroid Volume Surface Est. PGE Content (troy oz) ∆v Solar(km 3 ) density Pt Pd Au (km/s) flux(g/cm^3)16 Psyche ~3.3×10 6 ~5 1.1×10 16 5.3×10 15 2.7×10 15 14.60 0.12216 Kleopatra ~670,000 ~3.5 1.5×10 15 7.5×10 14 3.8×10 14 14.10 0.131986 DA ~4 ~5 1.3×10 10 6.5×10 9 3.2×10 9 7.13 0.151950 DA ~0.8 ~5 2.6×10 9 1.3×10 9 6.4×10 8 6.86 0.40Notes: PGE contents were computed using the volume and surface density for each objectand the average concentrations from Table 2; Dv is the approximate velocity changerequired to go from low Earth orbit to the object; the solar flux is averaged over the orbitand expressed relative to Earth; 1986 DA and 1950 DA are on eccentric orbits that bringthem close to the Earth at intervals, while Kleopatra and Psyche never leave the asteroidbelt; volumes and surface densities are derived from radar observations (Ostro et al. 2002)assuming a discount rate of 6%. If theinitial cost is higher than $5 billion, thetime to repay increases. Costs up to $14billion would be repaid within a decade.The reserves in 1950 DA are comparableto the Bushveld Complex, althoughthe PGE concentrations are much higher(Cawthorn, 1999). At several times theextraction rate given above, the reserveswould last for centuries. If the profitsfrom the mission described are appliedexclusively to financing additional missions,the revenue can exceed $7 billion/yrwithin a decade of the start of thefirst mission.No one has applied carbonyl techniquesin space on any scale, so a technologydemonstration mission would bethe logical first step in a mining venture.One such mission would be a 1/100 th -scale version of the mission describedabove, obviously without a crew. Thedemonstration: go to 1950 DA, processsome tens of tonnes of material andreturn the resulting kilogram of PGE toEarth. This smaller spacecraft would costsome hundreds of millions of U.S. dollars,because fixed costs such as the launchvehicle must be considered.The potential of asteroid mining istheoretically great, although the cost ofany large-scale mission is quite high.There are good launch opportunities to1950 DA throughout much of this century.A demonstration mission could belaunched in 2008 or 2010, with the largemission launching a few years later. Thefirst profits would be made within adecade of today.ACKNOWLEDGMENTSThe author thanks Roger Scoon for hishelpful review.REFERENCESCawthorn, R.G., 1999, Platinum and palladiumresources of the Bushveld Complex: SouthAfrican Journal of Science, Nov/Dec 1999.Crocket, J.H, 1972, Some aspects of the geochemistryof Ru, Os, Ir and Pt in iron meteorites:Geochimica et Cosmochimica Acta, v.36, p. 517–535.Goldberg, E., Uchiyama, A., Brown, H., 1951,The Distribution of nickel, cobalt, gallium,palladium and gold in iron meteorites: Geochimicaet Cosmochimica Acta, v. 2, p. 1-25.Impala Platinum, 2005, 2005 Annual Report:Johannesburg, Impala Platinum.Krinov, E.L., 1960, Principles of meteoritics,Oxford, Pergamon Press.Lewis, S.J. and Lewis, R.S., 1987, SpaceResources, Columbia University Press.Ostro, S.J., Hudson, R.S., Benner, L.A.M.,Giorgini, J.D., Magri, C., Margot, J.-L.,andNolan, M.C., 2002, Asteroid radar astronomy,Asteroids III: Tucson, University of ArizonaPress, p. 151–168 p. 1