Apollo 12 - A New Vista for Lunar Science

8/7/2019 Apollo 12 - A New Vista for Lunar Science

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TheLuna rFie ldTr ips

Conrad starts dins n the ladder (attached to one of I n t r ep id ' sstruts) toward the Nloon's surface as Bean photographs

him through the hatch.

SeismometerThe ALSEP Seismometer reportedthe ascent of the LM and itsviolent return as well as thefootsteps of the astronauts as theywent about their lunar duties.Within z short time after itsdeployment, it had recorded tenr , vents of natural origin which !aasedirom 20 to 40 minutesprobablymicrometeorite hitsalthoughas one experimenter put it, noself-respecting geologist would havesaid so before the Apollo 12mission. As lunar night fell, the thinlayer of igneous mantle rockscalled a regoliththat underlies themaria in the vicinity of the Apollo 12landing site was twisted and tiltedby the rapid drop in temperature.The seismometer recorded thisgeologic unrest.This instrument which was unveilingthe mysteries of the Moon's internalstructure is perhaps as remarkableas the data it transmitted. As part

of a geophysical station that hasno peer on the Moonor onEarththe seismometer is a marvelof compactness and sensitivity.Equivalent instruments inEarth-based observatories would heten times larger. The ALSEPinstrument is 16" hEgh and weighs20 Pounds. It is so sensitive that itwould he useless on the dynamicand quake-ridden Earth. Wind andwave metion alone would dominatethe instrument. It is "criticallydamped" so that there is noresonance. A shock is recordedonce and the sensor is instantlyready to record the next one.

The geological survey conductedby the two astronauts occupieda small fraction of the first walk onthe Moon's surface and most of thesecond walk. Geologists at theManned Spacecraft Center atHouston were delighted with theperformance of their exuberantproxies on the Moon's surface. Therunning commentary maintainedby Conrad and Lunar Module PilotAlan L. Bean enabled the scientiststo determine that the assignedtasks were properly executed andalso provided on-the-spotobservations that could be linkedto specific locations andparticular samples that theastronauts were collecting. Onegeologist described the astronautsas "real rockhounds": high praisefrom a professional.I n t , c u pid, as the LM was named,landed some 25 feet from the rimof the crater containingSurveyor, Conrad described thesurrounding area as "sort of likean undulating plain." "1'm sure,"


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Ana,irm),uu pnyrares an AL-SLN r.+pennu nt t ,r mo.enientUr the rte where it will he set up. At right, theS-band ch,h antenna.

he said, "that some of these rockshave different colors and differ( nttextures, but from here in thespacecraft . . . they all apr. ar tobe of the same material and theyall appear to be pure white."Subsequently, while on thesecond walk, both Conrad andBean were to report grey, tan andbrown tones which theytentatively linked to the Sun'sangle of elevation and whetherthey were looking down-Sun oracross it.They reported rock-rimmedcraters of varying sizes in almostevery direction. Some of theboulders were very large, on theorder of 20 feet. They also notedwhat they suspected was bedrock.Conrad was first out of the LMand began his chores with anebullience that was to characterizethe actions of both astronautsthroughout their time on the lunarsurface. The first momentsoutside %s ere spent gettingacclimated to a lunar gravity

one-sixth that of Earth's. Conradcommented: "I have the distinctimpression I don't want to movetoo rapidly. But I can walk quitewell."After an exchange with Houston,Bean told Conrad, "Boy, you surelean forward." Conrad rejoined,". . . don't think you're gonnasteam around here quite as fast asyou thought you were."The powder-like dust on theMoon's surface that was to plaguethe astronauts throughout boththeir walks was quickly evident. Iteddied in a thick cloud below theLM as the spacecraft approachedthe lunar surface, forcingConrad to land on instruments.As Conrad took his first steps onthe Moon, Bean told him, ".. .your boots are digging in thesoil quite a bit . . . yourleft foot has a big mound ahead ofit right now just pushing along."As they unloaded the LM with thepulley arrangement, bothreported they were getting dirty.

The dust quickly coated theALSEP (Apollo Lunar SurfaceExperiments Package) instrumentseven as they were beingdeployed. One astronautcommented, "There's no way tohandle all this equipment withall the dust on it. Every timeyou move something the dustflies . . . goes %vay up in theair and comes in and landson you."Conrad's first task was collectingthe contingency sample, a bagfulof black soil. With Beanassisting he undertook to deploythe S-band antenna, a dish-shapeddevice to augment their radiosignal strength, and encounteredthe first of a sequence of min.-)rproblems with their equip. lent.They had trouble getting theantenna into a stable positionand finally resolved the matter bypushing the legs of the supportingtripod into the lunar surface.After planting the American flag,the astronauts set about deploying


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Bean lifts the hot plutonium core, sheathedin its cask, from its place of storageaboard the In t repid. The generator

is in the foreground

Assembling the ALSLI, mstrurnents on thebar-hell preparatory to carrying them to thedeployment site.

Surface MagnetometerA component of the ALSEP thatreturned unexpected informationwas the surface magnetometer,designed to determine if there wasa lunar magnetic field and,if so, to measure it.The instrument also provideddata on the electromagneticdisturbances created by the solarwind. In addition to the light itgives out, the un radiates vastquantities of ionized particles ofenergy spun out into space attremendous velocities. This "wind"also contains magnetic fields thatgeophysicists want to measure.Finally, besides its electromagneticeffect, the extent to which the solarwind penetrates the Moon will assistin determining the Moon'scomposition.

The magnetometer recorded amagnetic field with its focus 600feet from the instrumentadistance that could be either verticalor lateral. This field could extendover half the Moon's surface.Though very weak, themagnetometer reported it at leastfour times stronger than thatrecorded by the Explorer satelliteIMP (for Interplanetary MonitoringPlatform) from its orbit above theMoon. The IMP read the fieldstrength at 5 gamma while thesurface magnetometer set the levelat between 20 and 30 gamma. Forpurposes of comparison, Earth'smagnetic field is 23,000 gamma.The new data suggests that theMoon's magnetic field is close to

the lunar surface within a matterof feetand perhaps a property ofthe lunar structure. It is possible thatit is held to this low altitude by theforce of the solar wind.Early in its period of operation,the magnetometer passed throughthe bow shock wave which iscreated by the encounter of the solarwind with Earth's geomagnetic tail.This wave and an adjacent area ofturbulence on the side of the waveaway from the solar wind are ofparticular interest to science. Asit passed through the bow shock,the instrument recorded threeseparate "bounces" with values of90 gamma, 120 gamma and 80gamma, the highest ever recordedin the vicinity of the Moon.These "bounces" lastedapproximately 3 minutes andwere several hours apart. Theycould have been caused byfluctuations in the bow shockstriking the magnetometer atrandom or could be attributed tosolar flares.


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Astronaut working at the ALSLP .its

1 1 utimgnrtrirm icr icvn(v tort,pround)whrrh provided new data on the M11oon's

rnagnc tic field.

the Central Station of the A L S L P distributesth r power generated by the SNAP 27.The station also transmits data to Earthand receives commands lrom Earth

Like the solar wind, the penetrationthese relatively strong impulsesachieve into the Moon providesinformation on its structure. Whenthe Moon's orbit swung the sensorclear of Earth's magnetic tail,readings dropped to 40 gamma,which was construed to be acombination of the effect of theMoon's internal field of 30 gammaand a solar wind field ofapproximately 10 gamma. It willrequire another magnetometer at adifferem sanding site to resolve thequestion of fundamentalimportanre: i.e., whether thefield is a property of the wholeMoon or merel y of an area of theMoon. Experimenters believe thatreadings from three complete 28-day lunar cycles will be neededbefore reliable average valuesare established.

tc ontinued from page 5)the powered instruments of theALSEP. They selected a spot about600 feet northwest of the LMon the far side of a small crater.This was so the instruments wouldnot be disturbed by the blast of theLM's ascent engine on lift-offfrom the Moon.The deployment was not withoutdifficulties. Despite the astronauts'initial efforts, the Lunar AtmosphereDetector toppled over on its sideand the aluminum skirt of theseismometer persisted in curlingup at the edges as a result of ithaving remained so long in therolled state in which it waspacked. The astronauts finally gotthe detector to remain uprightand a suggestion from Houstonto weight the edges of the skirtdown th some lunar dirtflattened the curl. Once they hadpulled the plutonium core outof its cask and inserted it intothe power center, three of theinstruments began operatingimmediately.

The astronauts continued in anorthwesterly direction from theALSEP passing within a few feet ofShelf crater, a feature about 1,000feet in diameter with large bouldersin its basin. They told Houston,"... we're looking down at this bigcrater and it looks rather old andit has bedrock at the bottom ...there are some big boulders restinginside the rim ... we don't see anyoutcrop of rocks either ... say,well, from the top of the rim downto about 20 feet." They passedsome small, very fresh cratersas well.For the return trip, they made a "U"turn and came back toward the LMon a course parallel to, and eastof, their outward track. They passeda mound that caused Bean toexclaim: "I don't know, Houston,what they are. They're just p ort ofmounds." After warning Houstonnot to take the following commentthe wrong way, he said, "It lookslike a small volcano only its justabout 4 feet high and abOL't 5 feet


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One of hvn mnunds reported by Bean,a feature that puled the geologists.

i he everpresent lunar dust, caught by the Sun's rays,a halo for an astronaut

across at the top. It slopes downto a base with a diameter of15 to 20 feet."There were two such moundstheonly two in the entire area of theirwalk or in the area they could covervisually. Geologists on the groundspeculated that they were piles ofcoarse materials ejected from acrater. The astronauts spotted ablock too large for the tongs, so onepushed it over to the other whopicked it up and stowed it in hissample bag.Under instructions to return to theLM for rest, the two astronauts setout for the spacecraft, stopping atintervals to pick up rocks that lookedinteresting after photographingthem in place. One of theseConrad described as a "pure pieceof glass."On reaching the vicinity of theLM, Bean sank the core tube some32 inches into the lunar surface,20 inches deeper than the Apollo 11

crew had been able to penetrateand with less resistance.When Conrad's time on the surfacereached 3 hours and 38 minutes,Houston advised that they had afair amount of consumablesremaining and not to rush too hardto get back into the spacecraft.The crew did their housekeeping,stowed their rock collections andthe core sample. They alsoattempted to clean up. "Man, arewe filthy. We need ... a whiskbroom." Then Conrad to Bean,"Dust me off and I'll dust you offand we'll get in."

The Power CenterThe instruments making up theALSEP got power from a centralsource unique in space history:a SNAP 27for Space NuclearAuxiliary Power. SNAP 27 is fueledby a rod of uranium 238. Removingthe rod from its cask, and'nserting it into the power unit wasperhaps the astronauts' most ticklishassignment of the mission.Extraordinary precautions had beentaken to prevent a slip ormishandling which would have hadserious consequences. When theastronauts attempted to extract therod from the shielded cask, it stuck.After repeated blows on the caskwith a hammer, the rod was freed,v,ithdrawn from its container, andinserted into the power unitwithout further difficulty. Theunit is generating 73.59 watts ofelectric power, higher than thedesign output. It has an operatinglife of at least 2 years.


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TheLongTraverse

A trai l of footpr ints on the lunar su rface. Object in theb.._kground is the color te levis ion camera that w as thought toh'sunstruck ear ly in the f i rst of 12's two Moon walks.

Lu ngAtmosphere DetectorThis instrument, which wasdesigned to measure the density ofthe very attenuated lunaratmosphere, was turned on betweenthe first and second walks of theApollo 12 crew. A highly sensitiveinstrument, its maximum reading isfor an atmosphere with a densityone-millionth that of Earth.For reasons that are not clear, theinstrument ceased functioningduring the second Moon walk anddid not respond to turn-oncommands. Astronaut Conradpassed it during his walk and it ispossible that the discharge of gasfrom his suit material overloadedthe sensor.

After a 5 hour sleep and aconference with Houston about thelong traverse planned for the secondMoon walk, Conrad and Bean ereready to return to the lunar sur..,ce.The traverse had been carefullypiotted so as to bring the astronautsto local features with a specialpotential for scientific finds. Theywere to leave the LM and skirt thenorthern rim of Head crateroneof the Snowman group Aftereaching the western side, theywere to pa between the inner pairof three small craters and proceednearly due south to Bench crater.From there they would swingwest-by-south to the smallcrater, Sharp.Next objective was Halo crater, asmall feature close to the southernrim of the crater in which Surveyorlay, east and north of Sharp. Theirrcute would then take them intoSurveyor crater and over to theSurveyor spacecraft for inspectionof the hardware and the removal ofselected components so that these

could be examined, on return toEarth, for the effects of a 31-monthexposure to the lunar environment.They would then exit from theSurveyor crater and travel westto the LM.Conrad began his observationswhile still in the spacecraft. "Thematerial around the spacecraft .. .looking into the Sun ... a very richbrown color like a good plowedfield ... down-Sun, it is still thesame ash grey." He called attentionto a 3 1/2-inch rock sitting, loose, 6inches from the engine bell of theLM that had not been blownaway by the engine exhaust althoughthe ground around it had beenswept "glassy clean."En route to Head crater, atHouston's request, the solar windcomposition experiment wasphotographed. Not a part of theALSEP powered unit, this was astrip of foil-like material shaped likea window shade designed to trapgas particles in the solar wind.


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I ocomotion in gravity 1/61hof Earth An astronaut getson hr, toes to begin a

lunar "lope."

A close-up of the Solar WindSpectrometer which isof the

"wind." A vast flow of theseat very high velocities.

data from the outset and itsthose of the magnetometer.

A second Solar Wind experiment. Thissheet of toil-like material was set up byConrad, shortly after leaving Intrepid, totrap particles in the "wind." Ineighteen hours of exposure. it confirmedthat a thin, high-velocity "wind" blowsacross the lunar surface. Each squarecentimeter of the foil was peppered withbetween six and seven million atomseach second.

The Seismometer which recorded Intrepid's crash landing onthe Moon, and other natural lunar events.

The astronauts began a treksouthward, picking up samples asthey went. They commented thatevery crater contained the glassbeads and described rounded rockswith skirts of surface dust on allsides. On approaching Bench crater,Conrad stated that it was verydifferent from Head crater, withwhat looked like bedrock on itsfloor and material that appeared tohave been melted. Bean thoughtthe tiny central peak in the crateralso had a melted appearance.Near the rim of Bench crater, theastronauts encountered rocks withan iridescent coating and othersthat were splattered with glass.The astronauts walked west about300 feet to Sharp crater which wassmall enough to raise doubts thatthey had located the right feature.Sharp had a white rim, raised about2 feet, of much softer materialthan had previously beenencountered. Surrounding thecrater was a radial pattern of rays.Bean trenched the area to a depth

of 8 inches and they took samples.Conrad then took a core tubesample from the bottom ofthe trench.Houston transmitted directions toHalo crater, the next stop. As theastronauts passed south of Benchcrater, they reported firmer footing.Bean said that, as he pushed off,the toes of his boots sank in about3 inches, but on landingflatfooted, the heels sank in only t/eof an inch. Conrad commentedthat in moving he felt like a girafferunning in slow motion. Bean toldHouston that he got the "decidedfeeling" he was going to sleep thatnight, and that he could go for agood drink of ice water.

Surface material in the vicinity ofHalo crater differed from the smoothtop layer over which the astronautshad been walking. Bean describedit as "more cohesive ... in clumps."They took a double core tubesample, using the hammer to drivethe tube its full 32-inch length intothe soil. One rock that caughtConrad's eye looked like "granite"(it wasn't) and had a large glasssplotch on it.In collecting samples, Bean deviseda means to make leaning over andpicking up a rock easier. Bygrasping a strap on Conrad'sbackpack and steadying him as hebent over, Bean compensated for theawkwardness resulting from therigidity of the pressurized spacesuitsand the difficulties with balance ina low-gravity environment. Conradadvised Houston th.c he had yet to

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An astronaut forces the core tube into thelunar surface to obtain subsurface samples

of lunar material.

The tongs used to helpthe astronauts pick up lunar rocks.

Ionosphere DetectorThe Ionosphere D etec tor , whichmeasures the lunar ionosphere , wa-inadvertent ly act ivated o nNovem ber 19th when the dustcovers were opened duringdeployment. I t returned interestintand use ful scient if ic data. Som eoutgassing took placethat caused arc i ng which doesno dam age to the ins trument ; bu tprevents i t from transmit+ing data.Experimenters turned the instrumentoff unt i l i t had purge d i tsel f of i tsgases. Th e interval a lso a l lowedt ime for the LM, which burps andgrunts l ike an overfed puppy forseveral days and thus muddles thedata coming from the sens ors, to dol ikewise. The senso r wascomm anded back into opera t ion inear ly December and has op eratedsucce ssfully since. In its earlystages the background data ratewas extremely low. This changedwhen the M oon 's cou rse brou ghtthe instrument back into sunl ight .

(continued from ^age 11)see any of the breccia differingmineral fragments in a binder ofanother kind of rockthatpredominated the samples broughtback by the Apollo 11 crew. Beanadded, "This is not at all likeNeil's run."The astronauts crossed the southernrim of Surveyor crater and followedthe approximate contour line onwhich Surveyor 3 rested, a curvingpath parallel to the rim. They toldHouston they weren't sinking veryfar, that the surface was "fairlyfirm stuff." They continued aroundthe rim toward the prize that theirprecision landing had won themSurveyor. The spacecraft had

bounced after touchdown and theimpressions made by its footpads atfirst contact with the surface werecarefully photographed.Conrad mentioned the brownish tintof Surveyor and learned fromHouston that, originally, theequipment bays, the primarystructure, and the struts were white.A closer inspection revealed that thespacecraft had taken on a coat ofthe everpresent dust. The mirrorused in Surveyor's photo system hadnot cracked, but was slightly warpedand was covered with a fine coatingof dust. Bean rubbed it with apiece of cloth attached to his wristand some of the coating came off.Scientists are curious whether thedust accumulated over a period oftime or whether it was blown onthe spacecraft by the landingof the LM.


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View of Surveyor 3 from Intrepid.

An astronaut prepares to cut off Surveyor'strenching scoop to return it to Earth

for analysis.

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Surveyor lootpad next to imprints left by its initial touchdowns.Imprints appear fresh despite 31 months of exposureto the lunar environment.

Approaching Surveyor from thesoutheast with Intrepid in the background.

Conrad and Bean unlimbered acutting tool and snipped off twopieces of tubingone painted andthe other unpainted. A tube thatthey had been assigned to getproved too thick and tough for thetool so they cut another. They alsocut off a length of cable, theSurveyor's trenching scoop, and thespacecraft's camera. With thesepieces of salvage, a laboratoryexamination would reveal how thevarious coatings reacted toprolonged exposure to the Moon'senvironment. The camera wouldshow how electrical, mechanical andsolid state components and thethermal control coating had beenaffected. All the parts would bechecked for chemical properties andthe scoop given a microbiologicalexamination. While at Surveyor,the astronauts completed a photoassignment and filled a bag fullof samples.Block crater, an impact featurewithin the larger Surveyor crater,was described as "fantastically

interesting," with a lot of bedrockin it and big, chunky rocks withsharp corners blown up out of it.On the way back to the LM, theastronauts collected additionalsamples and took more pictures.Among the last of the photos wasthe area under the engine of the LMthat had been swept clean of dustby the engine exhaust.The astronauts' experience inworking on the lunar surface willmake the Moon walks of their

successors easier and more efficient.Both Bean and Conrad were criticalof some of the equipment withwhich they had to work. On severaloccasions, Bean commented ondifficulties with the rock bags andnoted the need for sturdierconstruction. They had to make aquick fix on a set of scales and theywere less than pleased with thetool carrier. Houston made note ofthe problems with their handcameras, and the difficulties instabilizing ALSEP instruments willbe the subject of study before thenext Apollo launch. It may well bethat Bean's method of dealing withthe uncertainty of balance whileleaning over will result in futurespacesuits coming equipped witha handle on the back that a partnercan hold while the astronaut bends.

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Rejo in ingYankeeCl ipper

One of the critical maneuvers in alunar mission, where there is norecourse from an engine failure, isthe ascent from the lunar surface tore idezvous with the mother ship.The LM's designers entrusted thetask of boosting it back into lunarorbit to the ascent engine of theLM's upper stage, a constant-thrustrocket engine that engineers havedescribed as one of the world's mostbeautifully simple examples ofengineering design. Except for thebell-shaped nozzle, everycomponent of significance has abackup ready to take over in caseit fails.After an intensive checkout of thesystems of the upper stage, and alengthy exchange of situation checkswith Houston, Intrepid radioed,"The engine is fired." During theseconds following, Intrepidtransmitted a series of staccatoreports on the ascent.

"It's good.""Pitchover looking good."

Thirty seconds after liftoff thevwere 1,594 feet above the ;unarsurface."We're on our way. This programlooks good. Keeping right down thepike. What a nice ride."At 4 minutes and 8 seconds theywere travelling at 2,400 feet persecond relative to the Moon, andgaining speed. Seven minutes afterlift-off, velocity had built to 5,000feet per second. Seconds later, thecrew shut off the engine. Intrepidhad achieved lunar orbit.A s they started their catch-upmaneuvers with Yankee Cl ipper ,Conrad told Houston, "I sure doenjoy flying this thing." In t rep idand Y an ke e C l i p p e r steadily cut thedistance separating them from 140miles, to 80 miles and finally fro nnY an ke e Cl ippe r , "Hey, Pete, I'vegot you at 6/10 of a mile. Howcan you look so good if you'reso ugly?"

I n t r e p id : " I don't know. You lookawfully good yourself."Shortly after this exchange the twospacecraft were station keeping;and began the cautious, creepingfinal approach. Finally, from YankeeCl ipper , the active member in thedocking maneuver, ... .. and you'rehome free boys." In t rep idresponded, "Super job you did.That was cool, wasn't even a ripple."Yankee C l i p p e r and I n t rep i d werefirmly joined once more.

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Intrepid's pcm cred descent on its last flightpicks up speedfor science. The LM ...T h eL MReturnsto theMo o n In previous lunar missions, the LMascent stage has been jettisoned andfired into an orbit that wouldprevent its interfering with futuremissions. This time the Intrepidwas to make a last contribution toscience by being destroyed. Withthe crew reunited in the commandand service module the LM wascast off and driven from orbit intothe lunar surface. Traveling atapproximately 5,000 mph, the 5,500lb. (Earth weight) stage struck about45 miles from the ALSEPseismometer. The force of the blowLM delivered was about 30,000,000foot-pounds. On Earth, such anevent would register a minor tremorfor perhaps as long as 2 minuteson an Earth-type seismometer.

The results of the LM's impact onthe Moon's surface astounded thegeophysicists. The shock wavesregistered on the lunar seismometerfor 55minutes, building upto a peak at the 8-minute markand then slowly declining. Dr.Maurice Ewing of LamontObservatory exclaimed: "It was asthough one had struck a bell in achurch belfry a single blow and itsreverberation had continued for55 minutes." The phenomenon wascompletely outside any experienceon Earth.

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. . . as it arches down... toward (lie lunar surface.Early examination of theseismometer data reveals that thesignal was received on the threepipe-like axes of the instrument thatparallel the surface, but not on thevertical axis. If the vertical axis wasfunctioning, this established thatthe shock wave traveled through thesurface strata but lacked thestrength to penetrate deep into theMoon and bounce back to theinstrument. The signal was of lowfrequency and extremely lowvelocity: less than the velocity ofsound in air.

The team of investigators offeredseveral tentative hypotheses. Themost plausible was that the shockwaves traveled through a severelyfragmented structure--a rubblethat was sandwiched between tworeflective rock layers, the deepestof which was roughly 10 kilometersbelow the lunar surface. In thisformation, they bounced back andforth as they would in an echochamber.Crashing the LM into the Moonprovided the investigators with aninvaluable yardstick for readingseismic data. The mass, velocity andpoint of impact of the LM wereprecisely known. It is thus possibleto evaluate signals produced byother events by comparing themwith the "gong" produced bythe LM.The more than 20 events recordedb the Apollo 11 seismometer sinceJuly 1969 can now be correctlyinterpreted, as well as readingsfrom the instrument carried on theApollo 12 mission.

Geophysicists are now awaitingApollo 13 which will crash the largerSaturn V third stage into the Moonat a point from 200 to 400 milesfrom the seismometer. The moresevere the impact, the moreinformation it will yield.

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A m it rock duv(tl) onrh r the 6Urepid. the exhaust sweptthe adjacrnt udacri clear of dust hue did not mrnr the rock.

Another lunar rock With an iridescent coating.

AVeritableFeastDespite chuckles and whoops, andConrad's humming from time totime, the sample collection that thecrew of Apollo 12 brought backto Houston, and the commentary thecrew supplied, verified the fact thatthey were indeed good "rockhounds." While the study of thesamples and accompanying picturesis still in the preliminary stages,scientists are suggesting unique, andheretofore not possible, modelswhich will lead to an understandingof the complex composition andhistory of the Moon.The total of returned samples fromApollo 12 was approximately 75pounds. The rocks vary from fine toc r - - rse grained. One crystallineruck was very unusual because oflarge crystals more than 1 inchlong. While scientists are notagreed on how such crystals mayhave been formed, to one school ofthought, this indicates highpressures and temperatures andslow cooling. This group believesthat such slow cooling occurs onlyat depths of more than a kilometeror in a massive lava flow that iscooling at its base. Another groupof scientists ascribe to the"Hot-Moon" model. They suggestthat these large crystals are evidencethat the Moon was once made upof hot, igneous rocks formed from asilicate liquid. They are not certainwhat caused the meltingperhapsvolcanism or perhaps impact ofvery large meteoroids; but whatever it was, they believe the Moonmay have been hot for a long timefrom 500 million to a billion years.Age determinations on samplesfrom both Apollo missionssuggest this.In their lunar traverse, theastronauts covered three differenttypes of surface. One was groovedand was first observed by Conradin the area of the Lunar Module; asecond, the firmer surface thatConrad and Bean reported south ofBench crater; and the third, thesoft, powdery dust encounteredaround `harp crater and insideseveral of the very small craters.

Geologists are of the opinion thatthe surface layer of pulverizedmaterial has been extensivelychurned by micrometeorite impactswhich thoroughly mixed thematerials. One experimenterdescribed it as a "big blanket ofbeat up soil."The lunar samples lack hydratedminerals which suggests thatwater did not exist when they wereformed. There was no vesicularrock rock with smallspherical pockets in its matrix. Threeof the four large rocks gatheredby Bean near the end of the secondwalk were fine grained basalt withsome crystal-lined cavities presumably remnants of gasbubbles similar to those thatappeared in the samples collected

on Apollo 11. The fourth rock wasmuch coarser grained andchemically different from the Apollo11 samples. Its chemistry hasindicated that potassium,uranium and thorium are in greaterabundance while the titaniumcontent was less than half that ofrocks from the previous flight.While the samples returned onApollo 11 were 75 percent breccia,the breccia on Apollo 12 was lessthan 5 percent. Glass spheruleswere noted in both missions, butthere were fewer glass beads inApollo 12 material. The fine materialreturned was probably igneouslava that had cooled quickly with arapid escape of gases.One can say without question thatnew finds from Apollo 12 and thestriking variation from Apollo 11are dramatic proof that the Moon isan inhomogeneous body with avery complex history.

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Yankee Clipp er splashes down inchoppy seas.

TheLongVoyageH o m e

- - - --Melon PAll T im es ESTTime of Launc h 11 :22 a .m . 14 No vemberElapsed Time O utw ard leg 83 hou rs 25 m inutesEnter Lu nar Orb it 10 : 47 :23 p .m. 17 Novem berIn trepid L an ds o n M oo n 01 :54 :3 5 19 No vem :)erE l a p s e d T im e 1 s t W a lk " 3 hou rs 56 m inutesElapsed Time 2 nd W alk* 3 hou rs 49 minutesTo ta l T ime o n M oon 31 hou rs 31 m inutesIn t repid L if ts Of f M oo n 9 :25 :47 a .m . 20 No vemberLeave Lun ar Orbit 3:49:16 p .m . 21 Nov em b e rTotal T ime in Lu nar O rbit 88 hou rs 56 m inutesElapsed Time Hom eward L eg 72 hours 14 minutesS p l a s h d o w n 3 : 58 : 24 p .m. 24 No vemberE l a p s e d T i m e o f F l ig h t 244 hours 36 minute 25 secon dsTotal Distanc e Traveled 953AM Statu te M iles Time measured from opening to closing of hatch.

To accelerate Apollo 12 out oflunar orbit and into the narrow paththat would bring the spacecraftback on the right course for safere-entry and splashdown, the CSMengine was fired on the far sideof the Moon. In this segment oflunar orbit there was nocommunication between Houstonand the spacecraft.As the spacecraft emerged from inback of the Moon andcommunications were reestablished,Houston asked: "How are thingsup near the Moon?"Yankee Clipper replied: "Not toobad, but I think we're aboutready to leave."Houston said, "Glad to have youback."The response: "We haven't metanybody up here."A bit later, from the spacecraft,"HoustonApollo 12's movinghome."For the next minutes, the crewturned cameras on the recedingMoon "in true living color." Forthe benefit of Earth viewers, thelenses recorded the apparenttopographical roughness of theterrain in the vicinity of terminatorthe boundary between sunlight anddarkness which, under a low Sunangle, looked "fairly smooth."The problem of determining colorwas unresolved, even at 500nautical miles. Yankee Clipperreported: "The impression I get isthat it is really useless ... to havecolor out there because it is pureblack and white. It just doesn'tlook right, it's so black and white."For the next thousand miles, thecrew turned the TV camera onvarious lunar features and discussedthem with Houston. There was alsosome discussion, in retrospect, ofthe unusual characteristics ofmovement in the lunar environment.On the rock rolling experiment:"It was hard to get them going ...everybody had the idea that in

such light gravity things would rolldown rather easily ... that wasn'tthe case ... you got it going andit just sort of went along in animatedslow motion, but it kept going fora long, long 'Lime.""I found I couldn't walk ...wherever we went we loped and itjust didn't seem natural not to...."Of the space suit, "... doesn'talways want to bend like you wantto ... you can bend pretty wellat your knee ... at the ankles, but itdoesn't want to bend up near thetop of the thigh.When the dialogue had finished,the Moon had shrunk to a 6-inchsphere out the window ofYankee Clipper.Highlight of the return trip was theview of Earth's eclipse of the Sun.

Two mid-course corrections put thespacecraft on target and Apollo 12hit the water 3.5 nautical milesfrom the prime recovery ship,Hornet. The sea in the landingarea was rougher than in anyprevious splashdowns, and theYankee Clipper hit hard.On recovery, the crew wasimmediately transferred to themobile quarantine facility andremained there until they transferredto the Lunar Receiving Laboratoryat Houston.For this all-Navy crew, one phraseseemed especially apt:"Well done!"

Prepared by the Office of Public AffaiuKahA A e r ona u t i c s a nd S p a r e A d m i n is t r a t io nW a s h in g t o n . D C . 2 O S 4 6For ufe by the

Superintendent of Documents, U.S. GovernmentPrinting Office. Washington, D C 203(.!P r ir a . 6 6 c e n t s:ti G/0:197" 0-372-727


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