"Long before it's in the papers"
November 23, 2015


Asteroid mining could begin within a few decades, scientists claim

Nov. 23, 2015
Courtesy of Vanderbilt University
and World Science staff

The griz­zled as­ter­oid min­er is a stock char­ac­ter in sci­ence fic­tion. Now, two re­cent events—one le­gal, one tech­no­log­i­cal brought as­ter­oid min­ing clos­er to real­ity, ac­cord­ing to ex­perts.

The le­gal step took place when the U.S. Sen­ate’s Com­merce, Sci­ence and Trans­porta­t­ion Com­mit­tee passed a bill ti­tled H.R. 2262—SPACE Act of 2015. The bill in­cludes a mea­sure that gives in­di­vid­u­als or com­pa­nies own­er­ship of any ma­te­ri­al they mine in out­er space. Ac­cord­ing to one es­ti­mate, as­ter­oid min­ing could ul­ti­mately be­come a trillion-dollar mar­ket.

Pro­to­type of a a gamma-ray spec­trom­e­ter that weighs one pound and uses about three watts of elec­tric­i­ty but, its de­vel­op­ers say, can do the job of a full lab sys­tem that weighs 200 pounds and takes up ten cu­bic feet. (Cred­it: Burg­er Lab / Fisk Uni­ver­si­ty)

The tech­no­log­i­cal de­vel­op­ment is a new ver­sion of a de­vice, called a gam­ma-ray spec­tro­scope, said to be per­fectly suit­ed for de­tect­ing veins of gold, plat­i­num, rare earths and oth­er val­u­a­ble ma­te­ri­al hid­den with­in the as­ter­oids, moons and oth­er air­less ob­jects float­ing around the so­lar sys­tem.

The spec­tro­scope is a sen­sor that min­ers would need to sniff out these val­u­a­ble ma­te­ri­als.

The con­cept comes from a team of sci­en­tists from Van­der­bilt and Fisk Un­ivers­i­ties, both in Nash­ville, Tenn.; NASA’s Je­t Pro­pul­sion Lab­o­r­a­to­ry in Pas­a­de­na, Calif.; and the Plan­e­tary Sci­ence In­sti­tute, based in Tuc­scon, Ariz. 

The work is de­scribed in an ar­ti­cle pub­lished Oct. 23 in SPIE News­room, a pub­lica­t­ion of In­terna­t­ional So­ci­e­ty for Op­tics and Pho­ton­ics.

The tech­nol­o­gy ex­ploits the fact that high-en­er­gy par­t­i­cles called cos­mic rays con­tin­u­ally bom­bard all ob­jects in the so­lar sys­tem. When they strike, they smash atoms in the top lay­ers and pro­duce a show­er of sub­a­tom­ic par­t­i­cles, in­clud­ing neu­trons, which then col­lide with the atoms in the ma­te­ri­al to pro­duce a form of high-en­er­gy light called gam­ma rays. 

A gam­ma-ray spec­tro­scope meas­ures these rays, whose pre­cise char­ac­ter­is­tics can reveal the con­centra­t­ion of var­i­ous rock-forming el­e­ments as well as pre­cious met­als like gold and val­u­a­ble crys­tals like di­a­monds.

“S­pace mis­sions to the Moon, Mars, Mer­cu­ry and the as­ter­oid Ves­ta among oth­ers have in­clud­ed low-resolution spec­trom­e­ters, but it has tak­en months of ob­serva­t­ion time and great ex­pense to map their el­e­ment­al sur­face com­po­si­tions from or­bit,” said Van­der­bilt Un­ivers­ity as­tron­o­mer Kei­van Stas­sun, co-author of the re­port. 

“With our pro­posed sys­tem it should be pos­si­ble to meas­ure sub-sur­face el­e­ment­al abun­dances ac­cu­rate­ly, and to do it much more cheaply be­cause our sen­sors weigh less and re­quire less pow­er to op­er­ate.” 

The key to the new in­stru­ment is a re­cently dis­cov­ered ma­te­ri­al called europium-doped stron­ti­um io­dide, or SrI2. It’s a trans­par­ent crys­tal that can act as an ex­tremely ef­fi­cient gam­ma-ray de­tec­tor, the sci­en­tists said. It reg­is­ters the pas­sage of gam­ma rays by giv­ing off flashes of light.

“The gold stand­ard for gam­ma-ray spec­tros­co­py is the high pu­r­ity ger­ma­ni­um (HPGe) de­tec­tor,” said Van­der­bilt phys­i­cist Ar­nold Burg­er, who de­vel­oped the SrI2 de­tec­tor. “How­ever, it re­quires cry­o­gen­ic cool­ing so it is very bulky. It al­so needs vacuum-tube tech­nol­o­gy so it con­sumes too much en­er­gy to run on bat­ter­ies. SrI2 is­n’t quite as good as HPGe, but it is more than ad­e­quate to do the job and it is com­pact enough and its pow­er re­quirements low enough so that it can be used in space­craft and even placed on robotic lan­ders.”

The first com­mer­cial mis­sions to near­by as­ter­oids could launch as early as 2020, but it will be dec­ades be­fore as­ter­oid min­ing be­gins in ear­nest, the sci­en­tists pre­dicted. 

In the meantime, the tech­nol­o­gy promises to pro­vide sci­en­tists with new de­tails about the com­po­si­tion of the as­ter­oids, comets, moons and mi­nor plan­ets in the so­lar sys­tem, they added. That in­forma­t­ion should im­prove our un­der­stand­ing of how the so­lar sys­tem formed, and al­so help de­ter­mine wheth­er ob­jects that are head­ed to­ward Earth’s neigh­bor­hood are dan­ger­ous.

* * *

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The grizzled asteroid miner is a stock character in science fiction. Now, two recent events—one legal, one technological—have brought asteroid mining closer to reality, according to experts. The legal step took place when the U.S. Senate’s Commerce, Science and Transportation Committee passed a bill titled H.R. 2262—SPACE Act of 2015. The bill has measures designed to facilitate commercial space development, including one that gives individuals or companies ownership of any material they mine in outer space. According to one estimate, asteroid mining could ultimately become a trillion-dollar market. The technological development is a new version of a device, called a gamma-ray spectroscope, said to be perfectly suited for detecting veins of gold, platinum, rare earths and other valuable material hidden within the asteroids, moons and other airless objects floating around the solar system. The spectroscope is a sensor that miners would need to sniff out these valuable materials. The concept comes from a team of scientists from Vanderbilt and Fisk Universities, both in Nashville, Tenn.; NASA’s Jet Propulsion Laboratory in Pasadena, Calif.; and the Planetary Science Institute, based in Tucscon, Ariz. The work is described in an article published Oct. 23 in the SPIE Newsroom, a publication of International Society for Optics and Photonics. The technology exploits of the fact that high-energy particles called cosmic rays continually bombard all objects in the solar system. When they strike, they smash atoms in the top layers and producing a secondary shower of subatomic particles, including neutrons, which then collide with the atoms in the material to produce a form of high-energy light called gamma rays. A gamma-ray spectroscope measures these gamma rays, whose characteristics spectrum can be analyzed to determine the concentration of various important, rock-forming elements, as well as precious metals like gold and valuable crystals like diamonds. “Space missions to the Moon, Mars, Mercury and the asteroid Vesta among others have included low-resolution spectrometers, but it has taken months of observation time and great expense to map their elemental surface compositions from orbit,” said Vanderbilt University astronomer Keivan Stassun, co-author of the report. “With our proposed system it should be possible to measure sub-surface elemental abundances accurately, and to do it much more cheaply because our sensors weigh less and require less power to operate.” The key to the new instrument is a recently discovered material called europium-doped strontium iodide, or SrI2. It’s a transparent crystal that can act as an extremely efficient gamma-ray detector, the scientists explained. It registers the passage of gamma rays by giving off flashes of light that can be detected and recorded. “The gold standard for gamma-ray spectroscopy is the high purity germanium (HPGe) detector,” said Vanderbilt physicist Arnold Burger, who developed the SrI2 detector. “However, it requires cryogenic cooling so it is very bulky. It also needs vacuum-tube technology so it consumes too much energy to run on batteries. SrI2 isn’t quite as good HPGe, but it is more than adequate to do the job and it is compact enough and its power requirements low enough so that it can be used in spacecraft and even placed on robotic landers.” The first commercial missions to nearby asteroids could launch as early as 2020, but it will be decades before asteroid mining begins in earnest, the scientists predicted. In the meantime, the new spectroscopic technology promises to provide planetary scientists with new details about the chemical composition of the asteroids, comets, moons and minor planets in the solar system, they added. That information should improve our understanding of how the solar system formed, and also help determine whether objects that are headed toward Earth’s neighborhood are dangerous.