NEEP 533 Lecture #19

NEEP533 Course Notes (Spring 1999)
Resources from Space

Lecture #19: 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)

History of human interest in meteorites (Cowen, 1995)

METEORITE CHARACTERISTICS

* Stones: silicate dominated (96% of all falls)
* Chondrites (88%): * Primitive, unmelted, undifferentiated materials relative to solar abundances, 4.6 by old; * Abundances of rock-forming elements close to solar proportions; * Usually contain glassy "droplets" called chondrules
* Achondrites (8%): * Very silicate-rich igneous textured rocks (99% silicates and oxides); * Formed by density-dependent differentiation, i.e., in a gravity field; * Most 4.6 by old
* Stony-Irons (1% of all falls): * About 50% ferrous metal alloys, 50% silicates; * Apparently related to high pressure crystallization, such as in the mantle of a now disintegrated planet.
* Irons (3% of all falls): * About 99% metallic Fe-Ni-CO alloys; * Inclusions of FeS, phosphides, carbides, graphite, silicates; * Apparently related to high pressure crystallization, such as in the core of a now disintegrated planet.

ASTEROIDS (seen by light reflected from their surfaces)

Asteroids are delivered to Earth as a consequence of orbital resonances and other complexities between Jupiter, the asteroid belt and between the asteroids themselves, and close encounter with Mars (Greenberg, 1998)

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 stoney meteorites 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 spectral 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.

Reflectance spectra indicate many NEAs are similar to Main Belt Asteroids

Others appear to be extinct comet nuclei

Surface volatiles depleted

Inert crust seals remaining volatiles inside

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: 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)

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)

TWO ROTATION TUMBLING (5.4 AND 7.3 DAYS)

GENERAL PROPERTIES

ROTATION RATES

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

LESS THAN 2.3 HRS WITH THE AVE. 5 HRS

LIMIT FOR CENTRIFUGAL FORCE

SUGGESTS LOOSE RUBBLE WITH GRAVITATIONAL 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

HUBBLE SPACE TELESCOPE

TERRESTRIAL TELESCOPES

CRATERING ON ASTEROIDS (Veverka, et al, 1997)

CRATERS FORM WITH DIAMETERS COMPARABLE TO ASTEROIDS MEAN RADIUS

IMPACT DOES NOT BREAK UP BODY AT THIS SIZE

CRATER SIZE-FREQUENCY DISTRIBUTION SIMILAR TO THAT ON THE MOON

LARGE CRATERS HAVE NOT DISTROYED EACH OTHER

PROBABLY DUE TO ACCELERATION OF EJECTA TO ESCAPE VELOCITY

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, PARTICULARLY NEPTUNE

CENTAURS HAVE LIVES OF FEW MILLION YEARS

~80 KUIPER/EDGEWORTH BODIES DISCOVERED (Morbidelli, 1998; Ward and Hahn, 1998; Science News, 1998, 154, 310; EOS, 1999, 80,37-38)

INNER BELT

BEYOND NEPTUNE ORBIT BUT IN 3:2 ORBITAL PERIOD RESONANCE WITH NEPTUNE

INCLINED, ELLIPTICAL, DYMAMICALLY STABLE ORBITS

CLASSICAL BELT AND SCATTERED DISK

OUTSIDE THE 3:2 RESONANCE WITH NEPTUNE

LOW INCLINATION, CIRCULAR, NON-RESONANT ORBITS

SCATTERED CLASS

INCLINED, ELIPTICAL, VERY LARGE ORBITS

100-400 KM DIAMETERS

WIDE RANGE OF COLORS, GENERALY IN THE REDS OR GRAYS

TOTAL MASS 100S TIMES ASTEROID BELT

MAY HAVE INCLUDED PLUTO (2300 KM) AND ITS MOON CHARON (1100 KM, 6 HR ROTATION RATE) AND THE CENTAUR OBJECTS IN THE JUPITER /NEPTUNE REGION

PRIMORDIAL MASS ESTIMATE IS 30 EARTH MASSES

CURRENT MASS ESTIMATE IS 0.06-0.3 EARTH MASSES

EARLY INTERACTIONS WITH NEPTUNE AND/OR MASSIVE PLANETESIMALS MAY EXPLAIN THE DIFFERENCE

COULD THIS BE A SOURCE FOR THE IMPACTORS DURING THE LARGE BASIN STAGES OF LUNAR EVOLUTION AT 4.1-3.9 BY? (see lecture 10 and Malhotra, 1993))

CONSIDER THAT NEPTUNE MAY HAVE FIRST FORMED IN AN ORBIT CLOSER TO SATURN, GRADUALLY INCREASING ITS INTERATION WITH THE KUIPER/EDGEWORTH BELT OBJECTS, UNTIL AT ABOUT 4.1 BY, THAT INTERACTION BECAME MUCH MORE INTENSE AND LED TO THE PRESENT ORBITS AND DISTRIBUTION

OBJECT 1993C IN KUIPER BELT/EDGEWORTH BELT (Brown, 1997)

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

OBJECT 1996 TO66 IN KUIPER/EDGEWORTH BELT (Science News, 1998, 154, 310; Luu and Jewitt, 1998))

BRIGHTER THAN OTHER KNOWN OBJECTS

IR ABSORPTION ABSENT

~600 KM DIAMETER

6.25 HR ROTATION

LONG PERIOD COMETS' SOURCE IS OORT CLOUD

PERIODS GREATER THAN ~200 YEARS

POSTUALTED 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

D/H RATIO ~3.2 X 10^-4 ,VS 1.56 X 10^-4FOR TERRESTRIAL OCEAN WATER AND AN ESTIMATED SOLAR NEBULA VALUE OF <1 X 10^-4 (Meier, 1998)

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)

D/H RATIO ~3.3 +/- 0.8 X 10^-4 ,VS 1.56 X 10^-4FOR TERRESTRIAL OCEAN WATER AND AN ESTIMATED SOLAR NEBULA VALUE OF <1 X 10^-4 (Meier, 1998)

CN COMPOUNDS

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

THREE TAILS (EOS, 1998,79, 573-574):

BRIGHT WHITE DUST TAIL FORMED BYSOLAR RADIATION PRESSURE ON DUST

DIM BLUE ION TAIL FORMED BY SOLAR WIND AND COMETARY ION INTERACTION

SODIUM TAIL FORMED BY SOLAR RADIATION PRESSURE ON SODIUM ATOMS

X-RAY EMISSIONS DETECTED WITHIN ~2 AU OF THE SUN (Day, 1997)

CONFIRMED ON AT LEAST 4 OTHER COMETS

SHOEMAKER - LEVY ENCOUNTER WITH JUPITER

USE THE ABOVE LINK TO OBTAIN DETAILS ON THIS SPECTACULAR EVENT

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

SOMETHING MAY BE 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 ATMOSPHERES TOO LOW (see also Feuchtgruber, 1997)

NO EVIDENCE OR REQUIRED IMPACT RATE WHEN LUNAR SEISMETERS AND LUNAR ATMOSPHERE MONITORS ACTIVE IN THE 1970s

ENTRIES NOT OBSERVED OPTICALLY IN EARTH'S ATMOSPHERE

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

CONSENSUS HAS DEVELOPED THAT THIS IS NOISE IN THE DETECTORS (Science, 280, 1694-1695)

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 would 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, which a return to the Moon would give you, 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)

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

Whatever it might be, like ³He from the Moon, it must provide a timely 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 much more difficult than on the Moon
Recurring costs of sustained operations
Cost of capital

Like any new enterprise that requires more than about 3 years to begin to give a return on investment, mining the asteroids will need either bridge funds from the government or an early technology appication that can provide a foundation of investors and cash flow to support the primary enterprise.

SUMMARY OF RESOURCES OF THE ASTEROIDS AND NEAs
MUST COMPETE WITH THE MOON

CLOSER
GREATER CONCENTRATIONS IN SOME CASES
GREATER GRAVITY

POSSIBILITIES?

VOLATILES FROM CARBONACEOUS ASTEROIDS/SPENT COMETS

PHOBOS AND DEIMOS FOR USE RELATIVE TO MARS

GOLD AND PLATIMUM GROUP METALS

ASSUME 100 PPM PRECIOUS METAL CONCENTRATION
400,000 TONS WORTH ~$5T TODAY
EVEN AT DEFLATED PRICES DUE TO INCREASE SUPPLY THE VALUE WOULD BE INTERESTING

MAJOR COST FACTORS

LAUNCH

DEVELOPMENT COSTS MIGHT BE SHARED

SPACECRAFT
EXTRACTION AND PROCESSING IN LOW GRAVITY
RECURRING OPERATIONAL COSTS
COST OF CAPITAL

HIGH RISK = HIGH COST
REQUIRES HIGH RETURNS

BRIDGE FUNDS TO COVER 10-15 YEARS WITHOUT RETURN

GOVERNEMENT (?)
EARLY SPINOFF TECHNOLOGY (?)

INVESTORS
CASH FLOW

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:

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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

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Cowen, R. 1995, After the Fall, Science News, 148, 248-249

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NEEP533 Syllabus

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University of Wisconsin-Madison

Fusion Technology Institute

Lecture #19: So You Want to Mine an Asteroid!

Title: Evolution and Resources of the Asteroids and Comets

Notes:

References: