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Paul D. SpudisLunar and Planetary Institute

spudis@lpi.usra.edu

http://www.spudislunarresources.com

Introduction to the Moon

Moon 101NASA Johnson Space Center

4 June, 2008

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The Nature of the Moon

A rocky planetary object,differentiated into crust,mantle, and core

Heavily cratered surface;partly flooded by lava flowsover 3 Ga ago

Since then, only impacts bycomets and asteroids,grinding up surface intochaotic upper layer ofdebris (regolith)

Regolith is easily accessedand processed; likelyfeedstock for resourceextraction

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Some General Properties

2.2 x 1010

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Moon – Near and Far Sides

Near side Far side

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Moon – Elemental Composition

Iron (Fe) - maps mare basalts,mafic highlands (e.g., SPAbasin floor)

Titanium (Ti) - all mostly inmaria; high Ti ~ high H2

Thorium (Th) - asymmetricallydistributed in western nearside; maps KREEP

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Environment

Discontinuous butpredictable

(~1/2 time in Earth view)

Continuous on near side,Relay satellite needed for

far side

Direct Earth Communications

Solar wind gasesBound oxygen

Volatiles in shadows

Solar wind gasesBound oxygen

Resource Potential

> 150 ppm10-90 ppmH content

0 to 148 hrs(discontinuous)

~354 hrsDarkness

~530 to 708 hrs± 1.7º incidence angle

~354 hrs± 90º incidence angle

Sunlight

-50º C (lit) to -200º C (dark)-150º C to + 100º CTemperature

polarNon-polar

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Thermal Conditions

Surface temperature dependant on solarincidenceNoontime surfaces ~ 100° CColdest night temperatures ~ -150° C

Temperature variations minimal belowsurface > 30 cm (constant -23°± 5° C)

Polar areas are always either dark or atgrazing solar incidence

Lit areas have sunlight ~ 1 incidenceAverage temperatures ~ -50° ± 10° C

Dark areas are very coldUncertainty in lunar heat flow values

suggest cold traps between 50 and 70K (-220° to –200° C)

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MicrometeoritesNothing to impede impact of all-sized

debris; r.m.s. impact velocity ~ 20 km s-1

Estimated lunar impact hazard roughlyfactor of 4 lower than in LEO

Estimated flux:Crater Diameter (µm) # craters / m2 / yr0.1 3 x 105

> 1 1.2 x 104

>10 3 x 103

>100 6 x 10-1

>1000 1 x 10-3

Microcraters from 1-10 µm will be commonon exposed lunar surfaces

Craters ~100 µm dia. ~ 1 / m2 / yrEffects of secondary impact ejecta not well

quantified

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The Moon’s Orbit

Elliptical orbit, apogee405,540 km, perigee363,260 km

Earth-Moon barycenter ~1700km beneath Earth surface

Orbital period 27.3 daysMoon rotation 29.5 days (708

hours), sunrise to sunriseMoon orbital plane inclined

5.5º to eclipticMoon spin axis 1.5º

inclination from normal toecliptic

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History of the Moon’s Orbit

Moon is receding fromEarth at a rate of ~3.8cm/year due to tidalbraking

Implication is that Moonwas once much closer toEarthConfirmed by growth rings of

fossil coralsHistory of orientation of

orbital plane, spin axisuncertain; spin axis incurrent position for atleast last 2 Ga

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Moon’s Orbit and Eclipses

Orbital plane of Mooninclined 5.5º to ecliptic

Earth spin axis inclined23.5º to ecliptic

Line of nodes shifts 19.3º/year while perigee shifts40.7º /year

Line of nodes completesone full precession in18.61 years

Eclipses can only occurwhen line of nodescrosses orbital plane

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LibrationLongitudinal

Caused by Moon’s ellipticalorbit

Can see approx. 8° beyond90° W and 90° E limbs

Diurnal parallax ofobserver ~1° due todiameter of Earth

LatitudinalCaused by inclination of

lunar orbital planeCan see approx. 6.5°

beyond polar limbsDiurnal parallax of

observer ~1° due todiameter of Earth

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Topography

Global figure is roughly spherical, but withmajor departuresSouth Pole-Aitken basin on far side is

major featureMoon is very “bumpy”; extremes of

elevation + 8 km to –9 km (samedynamic range as Earth, sea floor tomountains)

Physiography divided into rough, complexbright highlands (terra) and relativelyflat, smooth dark lowlands (maria)

Landforms dominated by craters, rangingin size from micrometers to thousandsof km across

Smooth flat areas are rare, but occur inmaria (modulated by sub-km classcratering)

Average slopes: 4-5° in maria, 7-10° inhighlands

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New Kaguya Topographic Map

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Geodetic ControlDefining the coordinates of known

features in inertial spaceAll coordinates referenced to lunar

center-of-mass (CM)Best telescopic geodetic network

(1980) had positional accuracy of~ 4 km

Control network based on Apollophotography (1989) and sphere of1738 km radius had positionalaccuracy of meters in equatorialnear side; several km for parts offar side

New Unified Control Net 2005 usesApollo, VLBI, Clementine,referenced to USGS radii modeldeveloped from Clementine globallaser altimetry. Still multi-kmoffsets, especially on far side

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Moment of Inertia and CM-CF

Lunar Moment of Inertia 0.395 ±0.0023 (core < 400 km radius)

Center of Mass is offset ~2 kmtowards Earth from Center ofFigureResult of thicker far side crust (?)Responsible for more maria on near

side?Mass distribution asymmetric in

outer few tens km (mascons)Mass concentrations are

superisostatic crustal loadsResponsible for decay of lunar

orbitsAssociated with impact basinsFill by dense lava or uplifted

mantle?

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Surface Morphology and PhysiographyCraters dominate all other

landformsRange in size from micro- to

mega-metersShape and form change with

increasing size (bowl shaped tocentral peaks to multiple rings)

Maria are flat-lying to rolling plains,with crenulated ridgesLow relief, all mostly caused by

post-mare cratersFew minor landforms

Domes and conesFaults and grabenOther miscellaneous features

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Some Lunar Landscapes

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Lunar TerrainsMaria

Flat to gently rolling plainsNumerous craters D < 20 km;

larger craters rareBlockier (on average) than

highlands (bedrock iscloser to surface)

Mean (r.m.s.) slopes 4°- 5°

HighlandsRugged, cratered terrainSmoother intercrater areasNumerous craters D > 20 kmLarge blocks present, but

rare; “sandblasted” MoonMean (r.m.s.) slopes 7°- 10°

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Terrain SlopesMare – Flamsteed ring mare

Young mare; blocky crater rimsSmooth flat surfacesMean slopes < 5°; local slopes

(in fresh crater walls) up to25°

Highlands – Kant PlateauAncient highlands; few blocks,

but steep slopesRolling to undulating plainsMean slopes ~ 10°; local slopes

(inside craters) up to 30°

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Surface Lighting

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Surface Lighting

Apollo 12 EVA 1 - 7.5° Apollo 16 EVA 3 - 46°

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Surface Lighting

Apollo 12 EVA 1 downsun 7.5°

Apollo 17 EVA 1 upsun 16°

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Working in the DarkEarthlight and Artificial Illumination

FulldiskEarthilluminationequivalenttoworkinginroomlitby60Wbulb2.2metersoverhead

Thermalrequirementswillbegreatlyreducedfornightwork

Worknearthepoleswilllikelyrequireartificiallightinginanyevent

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RegolithThe layer or mantle of looseincoherent rock material, of whateverorigin, that nearly everywhereunderlies the surface of the land andrests on bedrock. A general term usedin reference to unconsolidated rock,alluvium or soil material on top of thebedrock. Regolith may be formed inplace or transported in from adjacentlands.

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Regolith

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RegolithMedian particle size of 40-130 µm

Average grain size 70 µm10-20% of the soil is finer than 20 µm

Dust (<50 µm) makes up 40-50% byvolume

95% of lunar regolith is < 1 mmSoil particle size distribution very

broad“Well graded” in geo-engineering terms“Very poorly sorted” in geologic terms

High specific surface area 0.5 m2 gm-1

8X surface area of spheres withequivalent particle size distribution

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Dust

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Loose Surficial Material

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Levitated Dust?

View of horizon glow from Surveyor

Vondrak

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Surveyor 3 Spacecraft

Spent 31 months on Moonprior to arrival of Apollo 12astronauts

Some dust coating on partsnoted, but patternsindicated the coatingsoccurred during Surveyorlanding and subsequentApollo 12 Lunar Modulelanding

No evidence of “levitated dust”settling on spacecraft

Care will have to be taken toassure landing spacecraftdo not spread dust overdeployed equipment andinstruments on surface

“The observed dust, therefore, originated from both theSurveyor and LM landings, with each contributing asignificant amount to various surfaces. "Lunartransport" seems to be relatively insignificant, if evidentat all.” – W. F. Carroll and P.M. Blair (1972)ANALYSIS OF SURVEYOR 3 MATERIAL AND PHOTOGRAPHSNASA SP-284, p. 28

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Laser Ranging Retroreflectors

Flown on Apollo 11, 14, and 15Array of glass cube corner

reflectors, deployed ~30 cmabove lunar surface

Astronauts deployed carefully,minimizing dust disturbance

Laser returns receivedimmediately and arrayscontinue in operation today

No evidence of any degradationin laser signal return overlifetime of arrays (Apollo 11LRRR on surface for 37 yearsnow)

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Lateral Dust Transport?Levitated dust could move laterally,

coating optics and equipment –does it?

Lateral transport on Moon appears tobe very inefficient

Compositional gradients at Apollosites are abrupt and well-preserved

Sharp contacts preserved in remote-sensing data, showing thatextensive lateral transport doesnot occur on the Moon

Surface rocks have clean surfaces;no evidence of deposited dustlayer

Mare Crisium – albedo and Fe concentration

Robinson and Jolliff, 2002

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Origin of the MoonThe traditional models

Intact captureMoon formed elsewhere and

was captured during aclose passage by Earth

FissionMoon spun off from molten,

rapidly rotating Earth

Binary (co-) accretionBoth Earth and Moon

accreted from smallbodies at same positionfrom sun

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LunarOriginGiantImpactHypothesis

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LunarHistoryandEvolution

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Lunar Robotic MissionsImpactors

Ranger - imagingSoft landers

Surveyor - imaging andchemical analysis

Luna 16, 20, 24 -sample returnLunakhod - long-range rover

OrbitersLunar Orbiter - global and site

mappingClementine - global mappingLunar Prospector - global

mappingSMART-1 - technology demo

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Current Lunar Missions

All polar orbiting global mappers,100 km altitude (200 km forChange’E; 50 km for LRO), 1-2 yrduration

Kaguya (SELENE)Every remote-sensor known toman

Chang’EImaging, microwave radiometry

Chandrayaan-1Imaging, altimetry, mineralogy,

SARLunar Reconnaissance Orbiter

Geodesy, thermal IR, neutron,SAR

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Existing and Future Lunar DataCoverage and Resolution

Property Present Future

Topography 30 km H; 50 m V 10 m H; 2 m VGeodesy 0.5 to 15 km global < 100 mMorphology 200 m; 5 bands 5 m; 8 bandsChemistry Th, Fe, Ti; 30 km All majors; 15-30 kmMineralogy Ol, Px, Plg; 200 m All; 80 mGravity near; 40 km ± 30 mgal global; 30 km ± 10 mgalMagnetic field global; 100 km ± 5 nT global; 100 km ± 1 nTAtmosphere detected; species ± 10% global; temporal ~days;

species ± 1%

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Suggested Reading

Wilhelms D.E. (1987) Geologic History of the Moon. USGS Prof. Paper 1348, 302 pp.Available at: http://ser.sese.asu.edu/GHM/

Heiken G., Vaniman D. and French B., eds. (1991) Lunar Sourcebook, Cambridge Univ.Press, 756 pp. CD-ROM version available; details at:https://www.lpi.usra.edu/store/products.cfm?cat=8

Spudis P.D. (1996) The Once and Future Moon, Smithsonian Institution Press,Washington DC, 308 pp. http://www.amazon.com/Future-Smithsonian-Library-Solar-System/dp/1560986344/ref=sr_1_1?ie=UTF8&s=books&qid=1212426761&sr=1-1

Wood C.A. (2003) The Modern Moon, Sky Publishing, Cambridge MA, 209 pp.http://www.amazon.com/Modern-Moon-Personal-View/dp/0933346999/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1212426952&sr=1-1

Bussey B. and Spudis P.D. (2004) The Clementine Atlas of the Moon, Cambridge Univ.Press, Cambridge UK, 376 pp. http://www.amazon.com/Clementine-Atlas-Moon-Ben-Bussey/dp/0521815282/ref=pd_sim_b_title_3

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Moon 101 - A Look Ahead

June 4, 2008 Introduction (Spudis) – motions, history of orbit/axis tilt, surface conditions, general properties,proposed origin.

June 18, 2008 Environment (Mendell) – thermal, radiation, plasma, electrical (including interactions with Earth’smagnetosphere), exosphere

July 2, 2008 Physiography and geology (Spudis) – terrains, landforms, topography (photogeology). Impact craterformation, excavation, ejecta emplacement, secondaries, impact melting and shock metamorphism, lunarmeteorites. Flux through time; cataclysm, periodicity, correlation with terrestrial record and other planets

July 16, 2008 Surface (Lindsay) – dust, rocks, slopes, trafficability (geotechnical properties). Formation and evolutionof regolith, interface with bedrock. Crater size-frequency distributions, exotic components, highland/mare mixing,vertical and lateral transport of material. Chemical and mineral composition, physical state, properties,characteristics

July 30, 2008 Crust (Lofgren) – formation and evolution, highland rocks types and magmatism, rock provinces andterranes; Volcanism: magma types, flood v. central vent eruptions, pyroclastics, number of flows, thicknesses,changes in composition with time, history; deformation and tectonic history

August 13, 2008 Interior (Plescia) – megaregolith, crustal thickness and variation, near side/far side dichotomy,mantle/core size, composition, heat flow, lunar magnetism, bulk composition

August 27, 2008 Poles (Bussey) – environment, sunlight and shadow, volatiles, opportunities and difficulties of livingand working at the poles

September 10, 2008 The Apollo Program (Eppler) - architecture, capabilities, evolution, surface exploration, roverexperience, advanced Apollo (cancelled missions)

September 24, 2008 Exploration (Eppler/Spudis)– geological reconnaissance and field work, surveys, traverses,transects, stratigraphy and the third dimension, bedrock on the Moon

October 8, 2008 Stations and observatories (Eppler/Spudis) – site selections and surveys, networks, emplacement,construction, alignment, maintenance

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For more information, go to:http://www.spudislunarresources.com

Or e-mail me at:

spudis@lpi.usra.edu