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Asteroid mining

Metallic asteroids have enough platinum group metals to be well worth mining. A football field sized asteroid has 1 billion dollars of platinum and 1 billion dollars of other platinum group metals. On the Earth, the best platinum mines are metallic asteroid impact craters, such as the Sudbury Crater in Canada and the Vrodefort Crater in South Africa.

Metallic asteroids can be mined either by distilling them in space or by bringing them to the Earth and mining them directly.

In space distillation, a space mirror focuses sunlight onto the asteroid to boil off the iron, leaving behind elements with boiling points higher than iron. These are the valuable elements. A 1 billion kg asteroid can be distilled down to 100 tons of platinum group metals and this is easily transported to the Earth.

A hydrogen bomb can propel the asteroid into crashing with the Earth and then the entire asteroid can be harvested, including the iron, nickel, and cobalt. The iron can be used as a carbon-free energy source and the cobalt is vital for lithium-ion batteries. Additionally, the hot spot from the asteroid impact can be harvested as geothermal energy.

The largest metallic asteroid is 16 Psyche, which has a diameter of 186 and contains 100 quadrillion dollars of platinum.

The value of the elements in a metallic asteroid is:

         Mass in    Element   Value of element
         asteroid   cost/kg   in the asteroid
          (tons)    ($/kg)    (Billions of $)

Platinum      19     55000    1.04
Nickel     67000        15    1.00
Rhodium        4.1   90000     .37
Iron      910000          .3   .27
Cobalt      6300        30     .19
Gold           1.8   60000     .108
Osmium         7.6   12000     .091
Germanium     37      2000     .074
Ruthenium     11      5500     .060
Palladium      3.8   14000     .053
Iridium        3.0   14000     .042
Gallium       80       280     .022
Zirconium      8      1600     .013
Rhenium         .85   5000     .004
Total    1000000              3.3
The most profitable elements are platinum, nickel, rhodium, iron, cobalt, and gold.


Sudbury basin, Canada

Sudbury, Canada
Sudbury geology

The Sudbury basin mine in Canada is a meteor crater from as 12 km metallic meteor that struck 1.8 billion years ago. The Earth's crust is poor in these elements because they sink to the core and platinum mines tend to be at sites of metallic asteroid impacts.

The asteroid belt was formed from a planet that was shattered by collisions. The asteroid belt comsists of mostly rocky asteroids and some metallic asteroids.

Platinum fraction in early universe    =   .005 parts/million
Platinum fraction in the sun           =   .009 parts/million
Platinum fraction in the Earth's crust =   .004 parts/million
Platinum fraction in Sudbury mine ore  =   .5   parts/million
Platinum fraction in iron asteroid     = 19     parts/million
Annual platinum production             =500     tons/year
Platinum used in mufflers              =130     tons/year

Space still

Alcohol still
Laphroaig distillery

The valuable elements in a metallic asteroid tend to have high boiling points. These elements can be isolated by heating the asteroid to 3200 Kelvin to boil off the low-value iron, nickel, and cobalt. After boiling, the asteroid has 1/5000 of its original size, has a value of 10 thousand dollars per kilogram, and is easily transported to the Earth.

Heat can be obtained by focusing sunlight with mirrors. The elements ranked by boiling point are:

          Density Melt  Boil   $/kg   ppm in metallic
          g/cm3    K     K               asteroid

Rhenium    21.0   3459  5869   4600         .85
Tungsten   19.25  3693  5828     50        8.1
Tantalum   16.7   3290  5731    400         .06
Osmium     22.59  3306  5285  12000        7.6
Thorium    11.7   2115  5061     25         .04
Niobium     8.75  2750  5017     40         .2
Molybdenum 10.28  2896  4912     21        7.3
Hafnium    13.31  2506  4876    500        0
Iridium    22.4   2739  4701  14000        3.0
Zirconium   6.52  2128  4682     20        8
Ruthenium  12.45  2607  4423   5500       11
Uranium    19.1   1405  4404     75         .007
Platinum   21.45  2041  4098  55000       19
Rhodium    12.41  2237  3968  90000        4.1
Vanadium    6.0   2183  3680     12        6
Titanium    4.51  1941  3560     10      100
Palladium  12.02  1828  3236  13600        3.8
Cobalt      8.90  1768  3200     30     6300
Nickel      8.91  1728  3186     15    67000
Iron        7.87  1811  3134       .3 910000

Metallic core

Moon
Titan
Ceres
Pluto


Element classification

Siderophile:  Iron-living. Tends to sink to the core along with the iron.
Lithophile:   Rock-loving. Tends to become included in rock and escapes sinking
              to the core.
Chalcophile:  Ore-loving. Tends to combine with oxygen and sulfur and escapes sinking
              to the core.
Atmophile:    Is a gas at room temperature and tends to escape the crust into the
              atmosphere.
In the early solar system, a small planet formed in the region that is now the asteroid belt. The planet had a hot interior and there was enough time for the dense elements to sink to the core. Then the planet was shattered by collisions and became the present-day asteroid belt. Pieces of the planet that are from the core are now metallic asteroids.
Solar abundance

Dot size  =  log(Solar Abundance)
Elements with a dot size of zero have no stable isotope.

Solar abundance data


Universe composition

Compositions are listed as parts per million by mass.

       Big Bang        Sun       Earth      Iron        Core
                                 crust    asteroid  Amplification

Hydrogen  750000      750000        1500        0        0
Helium    230000      230000                    0        0
Oxygen     10000        9000      460000        0        0
Carbon      5000        3000        1800     1100         .042
Iron        1100        1000       63000   910000        1
Silicon      700         900      270000       40         .000010
Tungsten        .0005       .004       1.1      8.1       .51
Platinum        .005        .009        .004   19      329
Gold            .0006       .001        .003    1.8     42
"Core amplification" is the degree to which the element is concentrated in the core, normalized so that the core amplification of iron is 1.
Core amplification

Platinum is more dense than iron and is hence more likely to sink to the Earth's core than iron. This is reflected in the "core amplification factor".

Platinum abundance in the crust =  cPt  =      .004 ppm
Iron abundance in the crust     =  cFe  = 63000     ppm
Platinum abundance in the core  =  CPt  =    19     ppm
Iron abundance in the core      =  CFe  =910000     ppm
Crust platinum/iron             =  cPt/cFe  =  .000000063
Core  platinum/iron             =  CPt/CFe  =  .000021
Core amplification factor       =  APt  =  (CPt/CFe) / (cPtcFe)  =  329
The elements with the highest core amplification factors are:
        Amplification   Density (g/cm3)

Ruthenium   762        12.4     Siderophile, Platinum group
Platinum    329        21.4     Siderophile, Platinum group
Rhodium     284        12.4     Siderophile, Platinum group
Osmium      263        22.6     Siderophile, Platinum group
Iridium     208        22.4     Siderophile, Platinum group
Nickel       52         8.9     Siderophile
Palladium    44        12.0     Siderophile, Platinum group
Gold         42        19.3     Siderophile
Rhenium      20        21.0     Siderophile
Cobalt       14.5       8.9     Siderophile
Selenium      4.2       4.81    Chalcophile
Germanium     1.8       5.32    Chalcophile
Bismuth       1.4       9.78    Chalcophile
Iron          1.0       7.9     Siderophile
Tungsten       .51     19.25    Lithophile
Molybdenum     .46     10.28    Siderophile
Mercury        .42     13.53    Chalcophile
Lead           .42     11.34    Chalcophile
Arsenic        .36      5.73    Chalcophile
Gallium        .29      5.91    Chalcophile
Copper         .13      8.96    Chalcophile
Tin            .063     7.26    Chalcophile
Silver         .030    10.49    Chalcophile
Zinc           .025     7.14    Chalcophile
Thorium        .00046  11.7     Lithophile
Uranium        .00027  19.1     Lithophile
Platinum group metals are the most likely to sink to the core. Almost all of the uranium and thorium resists sinking to the core, which is why nuclear energy is cheap.
Metallic asteroids

2011 UW158

"16 Psyche" is the largest metallic asteroid and is likely the core of a failed planet that had its mantle stripped away by collisions.

         Diameter   Perihelion   SemiMajor   Value    Value
            km          AU       Axis (AU)   (B$)     ($/kg)

16 Psyche   186         2.51       2.92     5⋅108      .02
Nereus         .33       .95       1.49        5      .033
Ryugu          .98       .96       1.19       95      .024
2011 UW158     .45      1.01       1.62        8      .021
Didymos        .8       1.01       1.64       84      .039
1989 ML        .6       1.10       1.27       14      .015
1992 TC       1.1       1.11       1.57       84      .015
The estimated value of each asteroid is from Wikipedia. Values are given for all asteroids except Psyche. In the table, we assume a price/mass for Psyche of .02 $/kg which leads to a value of 500000 trillion dollars, far larger than the Earth's annual gross domestic product of 75 trillion dollars.
Asteroid delivery

If a 1010 kg asteroid is broken with a hydrogen bomb then

Mass of the asteroid            =  M  =  1010 kg
Energy of the hydrogen bomb     =  E  =  .5 M V2  =  4e16 Joules   (10 megatons of TNT)
Speed of the asteroid fragments =  V  =  3 km/s
A hydrogen bomb is capable of moving an asteroid.
Vaporizing a metallic asteroid

A space mirror can be used to vaporize a metallic asteroid, which leaves behind elements with high boiling points. These elements are the valuable ones. We assume that the asteroid is mostly iron.

Asteroid original temperature   =  220 Kelvin
Asteroid boiling temperature    = 3200 Kelvin      (Boiling point of cobalt)
Melting energy of 1 kg of iron  =  272 kJoules
Boiling energy of 1 kg of iron  = 6090 kJoules
Iron solid heat capacity        = .449 kJoules/kg/Kelvin
Iron liquid heat capacity       = .82  kJoules/kg/Kelvin
Iron solid temperature change   = 1591 Kelvin      (From  220 Kelvin to 1811 Kelvin)
Iron liquid temperature change  = 1323 Kelvin      (From 1811 Kelvin to 3134 Kelvin)
Iron solid heating energy       =  714 kJoules     (Energy to heat from  220 to 1811 Kelvin)
Iron liquid heating energy      = 1085 kJoules     (Energy to heat from 1811 to 3134 Kelvin)
Iron total heating energy       = 8161 kJoules     (Energy to heat, melt, and vaporize)
Energy to vaporize iron asteroid=  8.2⋅1015 Joules  (Assume a mass of 1 billion kg)
Power from 10 km3 space mirror  =  1.3⋅1011 Watts
Time to vaporize asteroid       =60000 seconds  =  17 hours
Mass of a 10 km3 space mirror   =  600 tons
Vaporization accounts for most of the energy requirement.

A 10 km3 space mirror can vaporize a 1 billion kg asteroid on 1 day.

The exiting vapor can be passed through tungsten pipes heated to a temperature of 3250 Kelvin, just above the temperature of the vapor. Any platinum group metals in the vapor will condense onto the pipes. Tungsten is used because it is the element with the highest melting point (3695 Kelvin).


Economic impact

The iron in a metallic asteroid can be burned to produce carbon-free energy.

Fe + O2 → Fe2O3
An asteroid 3 km in diameter can supply civilization's energy for one year.
Energy density of iron         =   5.2 MJoules/kg
World energy production        =  6e20 MJoules/year
Iron to produce world's energy =1.2e14 kg
Iron density                   =  7900 kg/meter3
Radius of iron asteroid        =  1544 meters
Some of the metals in a metallic asteroid have the potential to overwhelm Earth production and reduce the price of the metal, opening new technological applications. These metals are osmium, ruthenium, iridium, rhodium, and platinum. For a 1 billion kg asteroid,
         Mass in   Annual Earth   Mass in asteroid
         asteroid     mining      / Annual Earth mining
          (tons)      (tons)

Osmium         7.6          1        7.6
Ruthenium     11           12         .92
Germanium     37          118         .31
Gallium       80          273         .29
Iridium        3.0         12         .25
Rhodium        4.1         30         .14
Platinum      19          245         .08
Cobalt      6300       110000         .057
Nickel     67000      2100000         .032
Rhenium         .85        50         .017
Palladium      3.8        250         .015
Gold           1.8       2800         .0006   Earth gold won't be eclipsed by asteroid gold
Iron      910000   1700000000         .0005
Zirconium      8       900000         .000009
Bringing a trillion kg asteroid to the Earth would satisfy the world's iron, nickel, and cobalt demand and then we wouldn't need to use energy for smelting.
Platinum production
           tons/year

World         161
South Africa  110
Russia         25
Zimbabwe       11
Canada          7.2
USA             3.7
Other           3.8
Data for 2014
Cosmic element abundance

Compositions are listed as parts per million by mass.

       Big Bang   Milky Way   Sun       Earth      Iron    Amplification
                                        crust    asteroid

Hydrogen  750000   739000   750000        1500        0        0
Helium    230000   240000   230000                    0        0
Oxygen     10000    10400     9000      460000        0        0
Carbon      5000     4600     3000        1800     1100         .042
Neon        1300     1340     1000                    0        0
Iron        1100     1090     1000       63000   910000        1
Nitrogen    1000      960     1000          20       33         .11
Silicon      700      650      900      270000       40         .000010
Magnesium    600      580      700       29000      320         .00076
Sulfur       500      440      400         420      360         .059
Calcium                                  50000      500         .00069
Potassium                                15000        0        0
Aluminum      50                60       82000       40         .000034
Sodium        20                40       23000        0        0
Phosphorus     7                 7        1000     2200         .15
Beryllium       .001              .0001      1.9      0        0
Lithium         .006              .0001     17        0        0
Boron           .001              .002       8.7      0        0
Fluorine        .4                .5       540        0        0
Chlorine       1                 8         170        0        0
Argon           .04             70                    0        0
Scandium        .03               .04       26        0        0
Titanium       3                 4        6600      100         .0010
Vanadium       1                  .4       190        6         .0022
Chromium      15                20         140       15         .0074
Manganese      8                10        1100      300         .019
Iron        1100     1090     1000       63000   910000        1
Cobalt         3                 4          30     6300       14.5
Nickel        60                80          90    67000       52
Copper          .06               .7        68      130         .13
Zinc            .3               2          79       28         .025
Gallium         .01               .04       19       80         .29
Germanium       .2                .2         1.4     37        1.8
Krypton         .04                                   0        0
Strontium                                  360        0        0
Ytterbium       .007              .01        2.8      0        0
Zirconium       .05               .04      130        8         .0043
Niobium         .002              .004      17         .2       .00081
Molybdenum      .005              .009       1.1      7.3       .46
Ruthenium       .004              .005        .001   11      762
Rhodium         .0006             .002        .001    4.1    284
Palladium       .002              .003        .006    3.8     44
Silver          .0006             .001        .08      .035     .030
Cadmium         .002              .006        .15      .02      .0092
Indium          .0003             .004        .16      .01      .0043
Tin             .004              .009       2.2      2         .063
Antimony        .0004             .001                 .34
Lutetium        .0001             .001                -
Hafnium         .0007             .001       3.3      0        0
Tantalum        .0001                        1.7       .06      .0024
Tungsten        .0005             .004       1.1      8.1       .51
Rhenium         .0002             .004        .003     .85    20
Osmium          .003              .002        .002    7.6    263
Iridium         .002              .002        .001    3.0    208
Platinum        .005              .009        .004   19      329
Gold            .0006             .001        .003    1.8     42
Mercury         .001              .02         .067    0         .42
Thallium        .0005             .001                0        0
Lead            .01               .01       10       60         .42
Bismuth         .0007             .01         .025     .5      1.4
Thorium         .0004             .0003      6         .04      .00046
Uranium         .0002             .001       1.8       .007     .00027
Neodymium                                   33
Lanthanum                                   34
Yttrium                                     29
Samarium                                     6
Cerium                                      60
Barium                                     340
Rubidium                                    60
Praseo                                       8.7
Gadolinium                                   5.2
Dysprosium                                   6.2
Erbium                                       3.0
Caesium                                      1.9
Europium                                     1.8
Arsenic                                      2.1     11         .36
Holmium                                      1.2
Terbium                                       .94
Thulium                                       .45
Bromine                                      3
Thallium                                      .53
Antimony                                      .2
Iodine                                        .49
Selenium                                      .05     3        4.2
Tellurium                                     .001

"Amplification" is the abundance of an element in a metallic asteroid divided by its abundance in the Earth's crust, with the value normalized so that it is "1" for iron.
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