NEEP 602 Lecture #18

NEEP602 Course Notes (Fall 1997)
Resources from Space

Lecture #18: So You Want to Mine an Asteroid!

Title: Evolution and Resources of the Asteroids and Comets

Notes:

METEORITES

General nature of meteorites (Lewis and Hutson, 1993)

METEORITE CHARACTERISTICS

* Stones: silicate dominated (96% of all falls)
* Chondrites (88%): * Primitive, unmelted, undifferentiated materials, 4.6 eons; * Abundances of rock-forming elements close to solar proportions; * Usually contain glassy "droplets" called chondrules
* Achondrites (8%): * Very silicate-rich igneous textured objects (99% silicates and oxides); * Formed by density-dependent differentiation (gravity field); * Most 4.6 eons
* Stony-Irons (1% of all falls): * About 50% ferrous metal alloys, 50% silicates
* Irons (3% of all falls): * About 99% metallic Fe-Ni-CO alloys
* Inclusions of FeS, phosphides, carbides, graphite, silicates

ASTEROIDS (seen by light reflected from their surfaces)

Main Belt Asteroids
- Orbital region between Mars and Jupiter
  
  Figure: Orbits of 100 largest known (NASA, 1992)
  951 Gaspra (from Galileo spacecraft, 16.200 km, Oct. 29, 1991)
  
  Meteorite reflectance spectra indicate most come from these asteroids
  Figure: Comparison of spectral reflectance (NASA 1992)
  However, there are major types of meteorites for which the asteroid parent is not known and major classes of asteroids for which there are no known meteorite analogs (Nelson, et al., 1993)
Near Earth Asteroids (NEA)
- Estimates are that about 1000 exist (Wetherill and Shoemaker, 1982)
- Ejected from Main Belt by interactions with Jupiter.
  - Collisions
  - Chaotic dynamics increase orbital eccentricity.
  - Relatively short (10-100 Myr) lifetimes and thus must be replenished rapidly compared to the age of the solar system. (Greenberg and Nolan, 1993)
  - Amor type
    - Orbit outside the Earth's
  - Apollo type
    - Orbit crosses Earth's with a period of > 1 year.
  - Aten type
    - Orbit crosses Earth's with a period of < 1 year.

EARTH-CROSSING ASTEROIDS (ECA)

Class of NEAs with the potential to impact our planet

Definition (Shoemaker, 1990): "...an object moving on a trajectory that is capable of intersecting the capture cross-section of the Earth as a result of on-going long-range gravitational perturbations due to the Earth and other planets. In this case "long-range" refers to periods of tens of thousands of years."
128 ECAs are known. (Their discovery, using current systems, depends on having an absolute magnitude >13.5 and varies with reflectivity of their surfaces as well as size.): 25% are Amors; 66% are Apollos; 9% are Atens
General Nature Majority are dark, C-type asteroids (carbonaceous chondrite meteorites) Low density, volatile-rich, much opaque (carbon-bearing?) material Current detectable minimum detectable size is 14 km. Many are S-type asteroids (chondrite and achondrite meteorites) Either stony, chondrite-like objects or stony-iron objects or a combination of the two. Current detectable minimum size is 7 km.: A few metallic (Ni-Fe) and basaltic types.
Physical characteristics: Highly irregular shapes; Well developed regoliths; Some very rapid spins; Some may be contact binaries or loose aggregates.

TYPES OF ASTEROIDS AND METEORITES

CHONDRITES (STONY - 80% OF OBSERVED METEORITE FALLS) (see Shu, et al., 1996)

(SILICATE-RICH CONTAINING SPHERICAL, GLASSY "CHONDRULES" RICH IN CA AND AL) SPECTRA SUGGEST SOURCE MAY BE HEBE IN MAIN BELT (Gaffey, M. reported in Science, 273, 1337) RIGHT POSITION RELATIVE TO JUPITER 4.56 B.Y. OLD 10⁷ YEAR SPREAD FOR CHONDRULE SOLIDIFICATION RESEMBLE THE SUN IN COMPOSITION REMNANT MAGNETISM INDICATES FIELD OF 1-10 G (Shu, et al., 1996) HIGH PRESSURE ASSEMBLAGES IN SHOCK VEINS (Ming, C. et al., 1996) FIRST STEPS IN TRANSFORMATION OF THE DUST OF THE NEBULA INTO PLANETS CHONDRULES MAY HAVE BEGUN AT 0.6 AU AND DRIVEN TO 2.5 AU+ (Shu, et al., 1996) SPECTRA OF 1862 APOLLO - NEA METAL, OLIVINE, AND PYROXENE 6 TELESCOPIC SPECTRA OF NEAs (Binzel, et al., 1996) SIMILAR WITH ORDINARY CHONDRITE METEORITE SPECTA ALTERATION (HYDROUS IN MANY) EITHER PREDATED OF POST DATED ACCRETION OF PARENT BODY (Brearley, 1997)

S-TYPE

29 TELESCOPIC SPECTRA (Binzel, et al., 1996)

INTERMEDIATE BETWEEN S-TYPE AND ORDINARY CHONDRITES

1. DISTINCT ROCK TYPES VS DIVERSE LARGER BODIES

2. ABUNDANCE OF OPAQUE MATERIALS

3. FRESH SURFACES (MOST LIKELY)

BASALTIC ACHONDRITES (6%)

VESTA [MAIN BELT PARENT(?)]

TOUTATIS - NEA (RADAR STUDY) (Science News, 148, 283)

"POTATO" SHAPED (TWO BODIES?)

TWO ROTATION TUMBLING (5.4 AND 7.3 DAYS)

CARBONACEOUS CHONDRITES

METALLIC ASTEROIDS

FIGURE: Estimated abundances of metals in asteroids (after Kargel, 1996)

GENERAL PROPERTIES

ROTATION RATES

SMALL ASTEROIDS (107/200M-10KM) ROTATE SLOWLY

LESS THAN 2.3 HRS/AVE. 5 HRS

LIMIT FOR CENTRIFUGAL FORCE

SUGGESTS LOOSE RUBBLE/GRAVITY BONDING (see also report in Science, 272, 485)

HIGHLY CRATERED REGOLITHS

MAJOR INFLUENCES ARE THE GAS GIANTS, PARTICULARLY JUPITER

SPACECRAFT OBSERVATIONS OF ASTEROIDS (RECENT AND NEAR FUTURE)

GALILEO

NEAR 253 MATILDE (1997 FLY-BY) LOW ALBEDO C-TYPE NEA (see EROS, 78, 285-286) Figure: Mathilde and comparisons ONLY 3-4% OF LIGHT REFLECTED/UNIFORM NO CHANGE OF ALBEDO IN CRATER WALLS OR FLOORS FAIRYCASTLE SURFACE STRUCTURE ON "WEATHERED" HYDROCARBONS FIVE LARGE CRATERS - ONE 10 KM DEEP! SHAPES SUGGEST INTERNAL FRACTURES DENSITY ~1.3 GM/CM3 (Science, 277, 30) MEAN DIAMETER 52 KM ROTATION 17 DAYS 433 EROS NEA - (1999 ORBIT) (see EROS, 77,73 & 79) 40X14X14 KM S-TYPE (METAL AND STONE)

HUBBLE SPACE TELESCOPE

TERRESTRIAL TELESCOPES 3671 DIONYSUS NEA (1997) 0.5 KM DIAMETER MOON (1/2 DIONYSUS) ORBIT ONLY FEW KMS ABOVE SURFACE

SPACE WEATHERING INFLUENCES ON ASTEROID SURFACES AND MATERIALS

MICROMETEORS
SOLAR WIND/SOLAR FLARE IONS
GALACTIC COSMIC RAYS
COLD/HEAT

COMETARY OBJECTS (see Whipple,1985)

SHORT PERIOD COMETS' SOURCE IS KUIPER/EDGEWORTH BELT (Luu and Jewitt, 1996)

PERIOD OF ~200 YEARS OR LESS

EJECTED BY INTERACTIONS WITH GAS GIANTS

CENTAURS HAVE LIVES OF FEW MILLION YEARS

32 BODIES DISCOVERED

BEYOND NEPTUNE ORBIT

ORBITS NEAR ECLIPTIC

100-400 KM

TOTAL MASS 100S TIMES ASTEROID BELT

MAY HAVE INCLUDED PLUTO (2300 KM) AND ITS MOON CHARON (1100 KM)

OBJECT 1993C IN KUIPER BELT (Brown, 1997)

SPECTRA SUGGEST HYDROCARBON ICE (METHANE, ETHANE, ETHELENE OR ACETYLENE AND POSSIBLY MORE COMPLEX COMPOUNDS)

LONG PERIOD COMETS' SOURCE IS OORT CLOUD

PERIODS GREATER THAN ~200 YEARS

SPHERICAL CLOUD AROUND THE SOLAR SYSTEM

100,000 AU DIAMETER

COMETS EJECTED BY INTERACTIONS WITH PASSING STARS (?)

MOST PROBABLY LOST TO SOLAR SYSTEM AFTER ONE PASS

SPECIFIC COMETS RECENTLY OBSERVED AND STUDIED

HALLEY Additional Halley Info (STUDIED BY FIVE SPACECRAFT IN 1986, INCLUDING ESA'S GIOTTO FLY-BY)

10 KM DIAMETER

NUCLEUS

IRREGULAR AND DARK

DENSITY -~1 GM/CM³

COMPOSITION

ICES (50%)

WATER (80%)

CO (15%)

FORMALDEHYDE, CO2, METHANE AND HYDROCYANIC ACID

DUST (50%)

ROCK

HYAKUTAKE (MAY 1996, see report in Science News, 149, 346-347)

2 KM DIAMETER/6.5 HR ROTATION

UNUSUAL X-RAY AND EUV EMISSIONS (Lisse, et al., 1996, Bingham, etal, 1997, Haberli, et al., 1997)

INTERACTION WITH SOLAR WIND AND SOLAR MAGNETIC FIELD

COMPOSTION

LITTLE CO

HALE-BOPP (See Cruikshank, 1997 and other papers in Science, v275)

Hubble images of comet

30-40 KM DIAMETER

COMPOSITION

CO₂, H₂0, CO, CH₃OH (Jewit, et al., 1996)

CN COMPOUNDS

C, N, AND S, ISOTOPIC RATIONS SHOW ORIGIN IN THE SOLAR SYSTEM AND NOT INTERSTELLAR (Jewitt, et al., 1997)

SHOEMAKER - LEVY

"HOUSE-SIZED SNOW BALLS" (See Frank, 1988, and 1997 report in Science, 276, 1333-1334)

SOMETHING IS CAUSING UV ADSORBING HOLES IN THE ATM

2-3000 KM ALTITUDE

O AND OH DETECTED

RATE SUFFICIENT TO PROVIDE EARTH'S OCEANS IF CONTINUOUS

BUT:

WATER CONCENTRATION IN PLANETARY ATMS TOO LOW (see also Feuchtgruber, 1997)

NO EVIDENCE WHEN LUNAR SEISMETERS ACTIVE

ENTRIES NOT OBSERVED OPTICALLY IN EARTH'S ATMOSPHERE

D/H RATIO FOR HALE-BOPP AND HYAKUTAKE VERY DIFFERENT THAN EARTH OCEANS

RESOURCES OF THE ASTEROIDS AND NEAs

Other than deflection of a threatening ECA, what might the capability to work at or near an ECA be used for?

Any resources we find on the Moon for use in space probably wopuld be found on the NEA, and in some case in significantly greater concentrations.

On the other hand, is there anything the Moon could not supply more economically and reliably?

Possibly the volatiles from carbonaceous asteroids, including spent comets nuclei: ie, water, CO, and CO2 (Nicholes, 1993, and Weissman and Campins, 1993)

On the other hand, if we had the capability to go to an ECA to deflect it, we could go to and NEA to get resources at small extra cost

Phobos and Deimos, low density asteroid-like moons of Mars, may provide supplies for Mars shuttlecraft.

What might be of commercial interest for use on Earth? (Kargel, 1994)

Whatever it might be, like ³He from the Moon, it must provide a return on investment commensurate with the risk of the loss of that investment.

Note that success would bring a drop in the price of the commodity of interest due to increased supply.
However, Kargel suggests that some NEAs, if judged only on the chemical analyses of meteorites, have sufficient gold and platinum group metals (Pt, Ir, Os, Pd, Rh, Ru) to pay a huge return on investment even in the face of significantly deflated prices.
- If a NEA 1 km in diameter contains 100 ppm precious metal (and some meteorites do) 400,000 tons of such metal could provide $320B at deflated market prices ($5.1T at current prices).
- At the lower prices, increased use may increase returns on the investment.

Major cost factors to consider:

Earth to asteroid launch costs (might be shared with cost to commercialize ³He and to have capability to deflect ECAs)
Spacecraft and extraction hardware costs (also might be so development cost sharing possible)
Low gravity fields at NEAs probably makes operations more difficult
Recurring costs of sustained operations
Cost of capital

Text:

NASA, 1992, pages 15-19

Neal, 1989, pages 181-191

Asteroid and Comet Impact Hazards

Link here to notes provided for information only; not included in NEEP602 Fall'97.

References:

Binzel, R.P. et al., 1996 Spectral propertiesof near-Earth asteroid: Evidence for sources of ordinary chondrite meteorites,Science, 273, 946-948

Brearley, A. Chondrites and the Solar Nebula,Science, 278, 76-77

Brown, R.H., et al., 1997, Surface composition of Kuiper Belt Object 1993C, Science, 276,937839

Bingham, R., et al., 1997, Generation of X-rays from Comet C/Hyakutake 1996 B2, Science 275, 49-51.

Cruikshank, D.P., 1997Stardust memories Science, 275, 1895-1896 (see other papers in this issue of Science)

Feuchtgruber, H., 1997, Nature, September 11, reported in Science News, 152, 200.

Frank, L, 1988, Science, p1408

Greenberg, R. and Nolan, M.C. , 1993, Dynamical relationships of near-Earth asteroids to Main-Belt asteroids, in Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 473-492.

Haberli, R.M, et al., 1997, Modeling of cometary X-rays caused by solar wind minor ions,Science 276, 939942

Jewitt, D.C., et al., 1996 Observations of Carbon Monoxide in Comet Hale-Bopp Science 1110-1113

Jewitt, D.C., et al., 1997 Measurements of 12cC/13C, 14N/15N, and 32S/34S Ratios in Comet Hale-Bopp (C/1995O1),Science, 278, 90-93

Kargel, J.S., 1994, Metalliferous asteroids as potential sources of precious metals, Journal of Geophysical Research, v 99, 21129-21141.

Kargel, J.S., 1996, Market value of asteroidal precious metals in an age of diminishing terrestrial resources, Space 96

Lewis, J.S., and Hutson M.L., 1993, Asteroidal resource opportunities suggested by meteorite data, in Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 523-542.

Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 977p.

Lisse,C.M., et al., 1996 Discovery of X-ray and Extreme Ultraviolet Emission from Comet C/Hyakutake 1996 B2, Science 274, 205-209.

Luu, J.X., and Jewitt, D.C., 1996, The Kuiper Belt, Scientific American, May, 44-52.

Ming, C., et al., 1996 The majorite-pyrope + magnesiowustite assemblage: constraints on the history of shock veins in chondrites, Science 271, 1570-1573

Mumma, J.M., et al., 1996, Detection of Aundant Ethane and Methane, Science,272, 1310-1314

Neal, V., et al., 1989, Extravehicular Activity in Mars Surface Exploration, Report on Advanced Extravehicular Activity Systems Requirements Definition Study, NASA-17779.

Nelson, M.L. et al., 1993, Review of Asteroid Compositions, in Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 493-522.

Nichols, C.R., 1993, Volatile products from carbonaceous asteroids, in Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 543-568.

Shoemaker, E.M., et al., 1990, Asteroid and comet flux in the neighborhood of Earth, in Geological Society of Americal Special Paper 247, 155-170.

Shu, F.H., et al., 1996, Toward an astrophysical theory of chondrites,Science, 271, 1545-1552

Thomas, P.C., 1997 Science, September 5 as reported in Science News, 152, 184.

Weissman, P.R., and Campins, H., 1993, Short-Period Comets, in Lewis, J.S., et al., 1993, Resources of Near-Earth Space, University of Arizona Press, 569-618.

Whipple, F.L., 1985, The Mystery of Comets, Smithsonian, Washington, 276p.

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University of Wisconsin-Madison

Fusion Technology Institute

Lecture #18: So You Want to Mine an Asteroid!

Title: Evolution and Resources of the Asteroids and Comets

Notes:

Text:

References: