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INTRODUCTIONIn the late 1600s, Galileo was thefirst to examine the Moon’ssurface with a telescope, and inthe 300 or so years since, we havelearned a great deal about theproperties of our nearest neighbor.Without leaving our planet wehave determined the Moon’s size,shape, and weight, how to measurethe temperature of the surface, andto estimate various electricalproperties from radar wavesreflected from the surface (1).However, investigators were notable to get a real handle on thegeology of the Moon until mineral

and soil samples were returned toEarth for close scrutiny.

Between 1969 and 1972 theNational Aeronautics and SpaceAdministration (NASA) success-fully landed 12 Apollo astronautson the lunar surface. The astro-nauts who visited the Mooncarefully collected 2, 196 docu-mented samples of lunar soils androcks weighing a total of 382kilograms during approximately80 hours of exploration (2). It isimportant to note that thesesamples were gathered from aharsh lunar environment thatincluded wildly fluctuatingtemperatures in an almost com-plete vacuum, potentially danger-

ous solar irradiation, and theuncertainty of return to Earth dueto equipment failure.

Geologists hoped that explora-tion of the lunar surface wouldestablish its composition, internalstructure, geological history, andevolution. In this respect it wasthought that the Moon wouldserve as a model for the earlyhistory of the Earth and the rest ofthe solar system. Yet, from theApollo missions, it has beendetermined that the Moon is farmore complex than previouslythought. The Earth’s only satel-lite, which was formed approxi-mately 4.6 billion years ago alongwith the rest of the planets, hasFigure 1 shown above left

Michael W. Davidson

NHMFL and MARTECH

The Florida State University

Tallahassee, Florida USA

MOON ROCKS UNDER THE MICROSCOPE

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completely melted and differenti-ated twice in its history. The firstmelting occurred very shortlyafter initial formation of the Moonand apparently resulted in awidespread molten ocean thatcooled to form a thick crust.While the satellite was cooling toform a solid body, several sectionsof the interior remelted, presum-

ably due to radioactive isotopicdecay, to form lava flows on theside facing the Earth (1-3).

STORAGE ANDPREPARATION OF LUNARSAMPLESThe lunar samples were stored insealed “rock boxes” during thereturn to Earth, although somesamples were exposed to theatmosphere of the Lunar LandingModule and the CommandModule. After arriving at theJohnson Space Center in Houston,Texas, all lunar samples werequarantined for 6 weeks in theLunar Receiving Laboratory toinsure the absence of extraterres-trial life forms (2). During thequarantine period, the sampleswere cataloged, photographed,and given a preliminary examina-tion. After more careful examina-tion, it became evident that lifeforms, organic molecules, and

water was absent from the lunarsamples and the quarantine wasdiscontinued for the later Apollomissions.

Lunar samples are stored andprepared for allocation to researchscientists in the Lunar CuratorialFacility at the Johnson SpaceCenter. This facility provides ahigh-efficiency air filtration

aluminum, teflon, and stainlesssteel. Investigators handling therocks use teflon overgloves andstainless steel tongs. These toolsare periodically cleaned with acidand rinsed in freon to avoid anycross-contamination of thesamples. Contamination byorganic substances in continu-ously monitored with ultraviolet

system that serves to remove dustand other particles from thelaboratory air to a degree of lessthan 1000 particles per cubic foot.A slightly positive air pressure ismaintained within the buildingand the floor plan restricts accessto the storage vaults so that areaswith the most traffic are separatedfrom areas where the samples arekept.

The samples are stored andexamined exclusively in nitrogen-filled glove boxes. Only ultrahigh purity nitrogen gas, producedby boiloff of liquid nitrogen, isused to store the rocks. Thissomewhat inert atmosphereprevents chemical changes in thesamples that would be unavoid-able in the open atmosphere. Themost severe reaction wouldprobably be oxidation of irongrains in the samples. The lunarsamples are only allowed to comeinto contact with three materials:

lamps. During storage, thesamples are kept in sealed teflonbags that are placed into stainlesssteel containers with bolt-on tops.A positive seal is provided by analuminum gasket between knifeedges on the top and bottom of thecontainer lid. The sample contain-ers are permanently stored innitrogen-filled cabinets in a bank-like vault with thick steel-rein-forced concrete walls.

Lunar samples probably serveas their own best containers sothey are not cut up unnecessarilyin an effort to avoid contamina-tion (2). When a sample is neededfor an investigation, it is trans-ferred into a glove box andremoved from its sealed container.A rigid protocol, designed tominimize contamination, is usedfor removing the various layers ofteflon bags. The glove boxes arecleaned with liquid freon betweensamples to prevent cross-contami-

Figure 2 Figure 3 Figure 4

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nation from sampledust, and only oneparent sample isallowed to occupy aglove box at anyparticular time. Also,separate glove boxesare used for eachApollo mission.

The procedure forprocessing lunarsamples involvescarefully weighing,photographing, anddescribing eachindividual sample. Asthe rocks are cut apart,each subsample is alsoweighed and photo-graphed. The photo-graphs all contain theimage of an orientationcube that relates theorientation of thesubsample to that of theparent and also to theoriginal lunar surfaceorientation. This isessential so thatorientation parametersare available for solarflare, cosmic ray and micromete-orite exposure studies. During thecutting process, the samples aredusted with nitrogen gas. Mapsare made of the saw cuts and theresulting surfaces of the rocksusing binocular microscopes. Thelarge rocks are initially cut apartwith a diamond-edged bandsawinside the nitrogen filled glovebox. Since it is impractical to coolthe surface of the rock during thiscutting procedure, some rocksprobably grow quite hot duringthis process. A certain degree ofcontamination is probably intro-duced at this point because ametal smear can be observed onthe sawn surfaces of some of thehardest rocks. The resulting slabsfrom large rocks and smallersamples are broken up with astainless steel chisel. Immediatelyafter completion of the subdivid-ing operation, the subsamples arereassembled into their original

positions and photographed as agroup for the purposes of docu-mentation. The photographs areused to construct three-dimen-sional maps that locate anyparticular subsample so thatinvestigators will be aware of theposition of their samples inrelation to others that mightappear in the scientific literature.

To prepare thin sections formicroscopy (2, 3), a sample isfirst impregnated with epoxyunder vacuum. Next, the sampleis cut with a diamond blade usingalcohol as a coolant and thenground flat with silicon carbidefollowed by polishing withdiamond. After polishing, thesample is affixed to a glassmicroscope slide with epoxy resin.The final preparation involvesgrinding the sample to an approxi-mate thickness of 100 micronsfollowed by hand polishing to a30 micron thickness using dia-

mond paste on bondpaper. Absolute ethylalcohol is used in allphases of this prepara-tion to avoid unwantedhydration of thesamples. Examination ofthin sections preparedfrom lunar samples isbest done with trans-mitted polarized light(see Figures 1-5).Using this technique,investigators can get ahandle on many of theproperties displayedby these samples.Characteristics such astwinning, melt inclu-sions, cracks, frac-tures, and zoning canbe readily documentedwith polarized lightmicroscopy. Inaddition, the birefrin-gence of the samplescan be recorded withquarter-wavelengthand one wavelengthretardation compensa-

tors. Many samples are quitecolorful under polarized light andcolor photomicrography can yieldbeautifully colored micrographs(Figures 1-4). Reflected lightmicroscopy also aids in theidentification of minerals presentin the samples and can be used tothe anisotropy and reflectivity ofthe samples. All photomicrographs of lunarsamples described in this reportwere recorded on a NikonOptiphot-Pol transmitted polar-ized light microscope equippedwith a UFX-III in-camera photo-multiplier system (4). Imageswere recorded on Fujichrome 64Tand were usually underexposed 1-3 f-steps by adjusting the ISOsetting on the exposure monitor.Kodak E-6 transparency reversalphotographic processing waschemically modified to enhancecontrast and color saturation. Inaddition, processing times were

Figure 5

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extended 30-45% in the firstdeveloper to “push” greatercontrast into the images (3).

EXAMINATION OF THELUNAR SAMPLESThe lunar surface can be roughlydivided into two domains. About20% of the Moon’s surface iscovered by dark lunar mares(Latin for seas) or lowlandregions. At a low sun angle, thelunar mares display wrinkle ridgesand flow fronts indicating thatthey are filled with frozen liquid.Before the Apollo missions, it wasthought that the mares wererelatively young because they areso poorly cratered (1, 2). TheApollo astronauts recovered alarge collection of samples fromthe mares which, to the surprise ofmany geologists, gave evidencethat the maria are extremely oldwith ages ranging from 3.1 to 3.8billion years. The mares are filledwith basaltic lava similar to thelavas found here on Earth. Marebasalts are volcanic lavas gener-ally rich in iron and titaniumoxide minerals that formed whenmolten rock from the interior ofthe Moon surfaced and cooled.For chemical purposes, the marebasalts can be divided into twogroups (2). An older high titaniumgroup with ages ranging from 3.5to 3.8 billion years was collectedfrom the Mare Tranquillitatis andTaurus-Littrow mare regions byApollo 11 and 17 astronauts, asample of which is illustrated inthe polarized photomicrographdisplayed in Figure 1. This basaltsample is rich in iron and titaniumand gave important first clues asto a lack of water on the moon andproved that the lunar maria arevery old. A younger, low titanium,group of basalts with ages rangingfrom 3.1 to 3.4 billion years wasrecovered by the Apollo 12 and 15astronauts. These age differencesand the wide variety of differentmare chemistries, where thetitanium oxide composition variesfrom 1 to 13 percent, indicates

magnification polarized transmit-ted light photomicrograph of animpact-melt breccia that wascollected from the lunar highlandsduring the Apollo 16 mission. Ascan be seen in the micrograph, itis a very dense and coherentsample with a distinctive poikilitictexture. This sample has beenstudied in detail by Albee and co-workers (6), and has been radioac-tivity-dated at about 3.93 billionyears.

The lunar surface is covered bya layer of disorganized debriswhich has been termed the lunarregolith (2). The thickness of thisregolith varies from about 5meters in the mare regions toapproximately 10 meters in thelunar highlands. A majority of theregolith is composed of a finegray soil with a density of about1.5 g/cm3, however the regolithalso contains breccias and frag-ments from the local bedrock.Figure 4 is a transmitted polarizedlight photomicrograph of a lunarregolith breccia recovered partway-up the slope of the Apenninefront by Apollo 15 astronauts.The sample was studied in detailby Simon and his colleagues (7)and has been found to contain awide variety of glass, mineral,and lithic fragments encapsulatedinto a brown glass matrix.

An unusual lunar sample wascollected from an orange soil neara small crater at the Apollo 17 site(2). This soil sample is thought tooriginate from the “dark mantle”that covers a wide area around thislunar landing site. Figure 5depicts a photomicrograph of thesample showing a composition ofsmall orange glass spheres,fragments of spheres, and blackdevitrified spheres. The samplealso contains a small amount ofmixed fragmental debris frommare basalts. The glass in thissample was probably from eitherlava fountaining, vapor condensa-tion following a meteorite impact,or from a meteorite impact into aliquid lava lake. Most lunar

that the mare basalts could nothave been generated from onecommon source region or commonparental magma through differentdegrees of partial melting. Figure2 is a low magnification polarizedtransmitted light photomicrographof a polished thin section (30 m)cut from a sample collected fromthe Oceanus Procellarum mareregion by Apollo 12 astronauts.Studies conducted on this sample(5) indicate that this is a lowtitanium, medium-grained,olivine basalt that possesses anexceptionally high magnesiumcontent. Large pyroxeneoikocrysts surround numerousrounded olivine crystallites, andpatches of glomerophric olivineare present in some areas. Thesample is composed primarily ofthe minerals olivine, plagioclaseand pyroxene with a trace amountof opaques. Chemically, the rockis about 42% silicon dioxide, 22%ferrous oxide, with the rest beingmainly magnesium, calcium, andaluminum oxides (2). Surrounding the mares are thelighter-colored hilly and moun-tainous highlands. The ruggedhighlands are covered withcountless small craters formedwhen meteorites struck the surfaceearly in the history of the Moon.The lunar mares also possesscraters, although not as manybecause the rate at which meteor-ites hit the Moon has decreasedwith time. Most of the rocksfound in the highlands are brec-cias, composed of lithifiedaggregates of clastic debris andmelt produced by meteoritebombardment of the lunar surface.Most of the breccias were recov-ered by the Apollo 14 and 16missions to the Fra Mauro andDescartes plains regions in thelunar highlands. These samplesproved to be very old with agesranging from 3.9 to 4.0 billionyears. Lunar breccias have a widevariety of matrix textures rangingfrom fragmental to vitric tocrystalline. Figure 3 is a high

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scientists now accept the lavafountain hypothesis because traceelement data do not support ameteorite origin.

Most of the minerals found inthe Moon rocks had already beenexamined and characterizedduring routine geological investi-gations of rocks found here on theEarth. The exception was threeminerals that could only havebeen produced under the extremeconditions found on the Moon. Anew mineral rich in titanium andiron oxides was named armalcoliteafter Neil Armstrong, EdwinAldrin, and Michael Collins,crew members of Apollo 11, thefirst mission to successfully land

on the Moon. Rocks found in thelunar highlands are generally richin the common white mineralfeldspar that is composed ofcalcium and aluminum silicates. Ahighly unusual class of rocksfound in the highlands was giventhe nickname KREEP (1, 2) afterits unique composition ofpotassium(K), rare-earth ele-ments (REE), and phosphorus (P).

The age of the lunar sampleswas determined by the abundanceratio of radioactive isotopes (2).

It has been found that the age ofmost highland rocks has beenreset by shock and heat producedby huge meteorite impacts. Fromradioactivity dating, researcherscan determine when these impactsoccurred. Most of the sampleshave ages centering around 4.0billion years, although some rockshave escaped meteoritic bombard-ment and are as old as the Moonitself (4.6 billion years).

In spite of all that has beenlearned from examination of lunarsamples, there is yet many unan-swered questions about the Moon.For instance, the most fundamen-tal question is still how the Moonwas formed. Theories range from

formation with the Earth as adouble-planet system, fission fromthe Earth followed by establish-ment of a new orbit, to capture bythe Earth as the Moon traveledthrough space. Another centralquestion is the asymmetry of theMoon. The side facing the earth isfilled with the dark mare regionswhile the opposite side is com-posed mostly of highlands. Whatinfluence did the presence of theEarth have on this phenomena?These and many other questions

remain unanswered until moreresearch can be conducted on thelunar samples and on the Moonitself. For a complete accounting,it may be necessary to ventureback to the surface of our nearestneighbor.

CREATIVEPHOTOMICROGRAPHYPhotography is slowly becomingrecognized as a legitimate art formand it’s increasing popularity isevidenced by the abundant use ofphotomicrographs as “eye-catchers” on the front covers ofbooks and periodicals (8, 9). Inthis respect, I have introduced aseries of multiple-exposure

photomicrographs,termed microscapes (4,9, 10), that are intendedto resemble surrealisticimaginary landscapes.Figure 6 is a microscapeentitled “Baghdad Afterthe Storm”, constructedwith Apollo 12 lunarsamples. The fore-ground is a singleexposure of a basalticlava sample collectedfrom the OceanusProcellarum mare regionby Apollo 12 astronautsand is intended toresemble rubble fromdestroyed buildings.After masking the lunarsample exposure bycovering a portion of thefield lens, a secondexposure is made with a

defocused epoxy resin bead and a530 nanometer retardation plate(the red cloudy sky). The risingsun effect is generated by reduc-ing the aperture of the fielddiaphragm and slightlydecentering the substage con-denser. After defocusing theshutter leaves, a red filter isplaced in the light path and a thirdexposure is made. The finalresult, as shown in Figure 6,resembles a hauntingly realisticimage. With careful experimenta-

Figure 6

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tion, a wide spectrum of photomi-crographs of this type can beassembled, limited only by theindividual photomicrographer’simagination.

AUTHOR’S BIOGRAPHYMichael W. Davidson is a researchscientist in charge of the opticaland scanning probe microscopyfacilities at the National HighMagnetic Field Laboratory at TheFlorida State University. Hisnumerous interests include thepackaging of DNA into virusheads, liquid crystallinity inbiological systems, and theinteraction of drug molecules withDNA. He has published numerousscientific articles in these fields.His photomicrography (photo-graphs taken through a micro-scope) has appeared on the coversof over 200 scientific and tradeperiodicals and books and he haswritten more than 50 articles onthe subject in popular photogra-phy magazines throughout theworld. In addition, he has won

over 30 awards in scientific andindustrial photography competi-tions. Framed prints of Davidson’sphotographs have been exhibitedat the American Association for theAdvancement of Science and theNational Research CouncilHeadquarters in Washington, D.C.,the International Center forPhotography and Sotheby’s in NewYork City, and the Los AngelesMunicipal Art Gallery. Mostrecently, Davidson’s photomicro-graphs have appeared on greetingcards, gift-wrap paper, T-shirts,trading cards, and calenders.

ACKNOWLEDGEMENTSThe author would like to thank theNational High Magnetic FieldLaboratory (NHMFL) for contin-ued support, and Drs. CharlesMeyer, John Dietrich, and JamesGooding of the Johnson SpaceCenter for helpful conversationsand providing the lunar samples.Microscopes used in this studywere provided by the NikonInstrument Group, Melville, NY.

REFERENCES

1. French, B. M., “What’s New on theMoon?” NASA Curatorial BranchPublication. 23 pages, 1980. For saleby the Superintendent of Documents,US governmental Printing Office,Washington, DC 20402.

2. Meyer, C., “The Lunar PetrographicThin Section Set”. NASA CuratorialBranch Publication Number 76. 61Pages 1987.

3. Davidson, M. W. and Lofgren, G.,“Photomicrography in the GeologicalSciences”. Journal of GeologicalEducation, 39, 403 (1991).

4. Davidson, M. W., “Some ArtisticTechniques in Photomicrography”.Journal of Biological Photography,59, 165 (1991).

5. Dungan, M. and Brown, R., “ThePetrology of the Apollo 12 Basalt Site”.Proceedings of the 8th Lunar ScienceConference, 1339 (1977).

6. Albee, A., Gancarz, A., andChodos, A., “Metamorphism of Apollo16 and 17 Metaclastic Rocks”.Proceedings of the 4th Lunar ScienceConference, 569, (1973).

7. Simon, S. Papike, J., and Gosselin,D., “Petrology of the Apollo 15Regolith Breccias” Geochimica etCosmochimica Acta, 50, 2675 (1986).

8. Davidson, M. W., “Getting YourPhotomicrographs Published”,Microscope Technology & News. 2, 4(1990).

9. Davidson, M. W. and Rill, R. L.,“Photomicrography. Common Groundfor Science and Art”. Microscopy &Analysis, Issue Number 11 page 7,May 1989.

10. Davidson, M. W., “Fabrication ofUnusual Art Forms with MultipleExposure Color Photomicrography”,The Microscope, 38, 689 (1990).

F I G U R E L E G E N D

Figure 1. Transmitted polarizedlight photomicrograph of 30 microme-ter thin section sample obtained fromthe Mare Tranquillitatis lunar regionby Apollo 11 astronauts “Buzz” Aldrinand Niel Armstrong. This basaltic lavasample is high in iron and titanium andis approximately 3.7 billion years old.

Figure 2. Transmitted polarizedlight photomicrograph of lunar basalticlava sample collected from theOceanus Procellarum mare region byApollo 12 astronauts. This sample is3.15 to 3.35 billion years old and gavethe first indications that Granite existson the moon.

Figure 3. Transmitted polarizedlight photomicrograph of a lunarimpact breccia sample collected fromthe Descartes highland plains region byApollo 16 astronauts. This sample is3.8 to 4.2 billion years old and gaveevidence that the lunar highland plainswere formed by meteorite impacts.

Figure 4. Transmitted polarized

light photomicrograph of a regolithbreccia consisting of a wide variety ofglass, mineral, and lithic fragments in abrown glass matrix. It was recoveredon the slope of the Apennine Front atthe Apollo 15 landing site.

Figure 5. An unusual orange soilcollected near a small crater at theApollo 17 landing site. The sample iscomposed primarily of small orangeglass spheres, and black devitrified(non-birefringent) spheres. The samplealso contains a small amount offragmental debris derived from marebasalts. This glass sample is approxi-mately 3.48 billion years old.

Figure 6. A microscape fabricatedwith lunar samples. The foreground isa basaltic lava sample recovered byApollo 12 astronauts. The cloudy skyis an epoxy resin bead defocused with a530nm retardation plate and a bluefilter inserted partially into the lightpath. The “sun” is the image of thefield diaphragm partially defocusedthrough a red filter and moved slightlyoff center.