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t　volcanic　flows　implies　massive　changes　in　50　or　100　years；　a　prediction　that　luckily　can　be　tested。　The　Voyager　images　of　to　can　be　pared　with　much　poorer　images　taken　by　ground…based　telescopes　50　years　earlier；　and　by　the　Hubble　Space　Telescope　13　years　later。　The　surprising　conclusion　seems　to　be　that　the　big　surface　markings　on　Io　have　hardly　changed　at　all。　Clearly；　we're　missing　something。



A　VOLCANO　in　one　sense　represents　the　insides　of　a　planet　gushing　out；　a　wound　that　eventually　heals　itself　by　cooling；　only　to　be　replaced　by　new　stigmata。　Different　worlds　have　different　insides。　The　discovery　of　liquid…sulfur　vulcanism　on　Io　was　a　little　like　finding　that　an　old　acquaintance；　when　cut；　bleeds　green。　You　had　no　idea　such　differences　were　possible。　He　seemed　so　ordinary。

We　are　naturally　eager　to　find　additional　signs　of　vulcanism　on　other　worlds。　On　Europa；　the　second　of　the　Galilean　moons　of　Jupiter　and　Io's　neighbor；　there　are　no　volcanic　mountains　at　all；　but　molten　ice—liquid　water—seems　to　have　gushed　to　the　surface　through　an　enormous　number　of　crisscrossing　dark　markings　before　freezing。　And　further　out；　among　the　moons　of　Saturn；　there　are　signs　that　liquid　water　has　gushed　up　from　the　interior　and　wiped　away　impact　craters。　Still；　we　have　never　seen　anything　that　might　plausibly　be　an　ice　volcano　in　either　the　Jupiter　or　Saturn　systems。　On　Triton；　we　may　have　observed　nitrogen　or　methane　vulcanism。

The　volcanos　of　other　worlds　provide　a　stirring　spectacle。　They　enhance　our　sense　of　wonder；　our　joy　in　the　beauty　and　diversity　of　the　Cosmos。　But　these　exotic　volcanos　perform　another　service　as　well：　They　help　us　to　know　the　volcanos　of　our　own　world—and　perhaps　will　help　one　day　even　to　predict　their　eruptions。　If　we　cannot　understand　what's　happening　in　other　circumstances；　where　the　physical　parameters　are　different；　how　deep　can　our　understanding　be　of　the　circumstance　of　most　concern　to　us？　A　general　theory　of　vulcanism　must　cover　all　cases。　When　we　stumble　upon　vast　volcanic　eminences　on　a　geologically　quiet　Mars；　when　we　discover　the　surface　of　Venus　wiped　clean　only　yesterday　by　floods　of　magma；　when　we　find　a　world　melted　not　by　the　heat　of　radioactive　decay；　as　on　Earth；　but　by　gravitational　tides　exerted　by　nearby　worlds；　when　we　observe　sulfur　rather　than　silicate　vulcanism；　and　when　we　begin　to　wonder；　in　the　moons　of　the　outer　planets；　whether　we　might　be　viewing　water；　ammonia；　nitrogen；　or　methane　vulcanism—then　we　are　learning　what　else　is　possible。




CHAPTER　13　　　THE　GIFT　OF　APOLLO

　

　

　

　

The　gates　of　Heaven　are　open　wide；

Off　I　ride　。　。　。

—CH'U　TZ'U　/ATTRIBUTED　TO　CH'U　YUAN）；　〃THE　NINE　SONGS；〃　SONG　V；　〃THE　GREAT　LORD　OF　LIVES〃　（CHINA；　CA。　THIRD　CENTURY　B。C。）

It's　a　sultry　night　in　July。　You've　fallen　asleep　in　the　armchair。　Abruptly；　you　startle　awake；　disoriented。　The　television　set　is　on；　but　not　the　sound。　You　strain　to　understand　what　you're　seeing。　Two　ghostly　white　figures　in　coveralls　and　helmets　are　softly　dancing　under　a　pitch…black　sky。　They　make　strange　little　skipping　motions；　which　propel　them　upward　amid　barely　perceptible　clouds　of　dust。　But　something　is　wrong。　They　take　too　long　to　e　down。　Encumbered　as　they　are；　they　seem　to　be　flying　a　little。　You　rub　your　eyes；　but　the　dreamlike　tableau　persists。

Of　all　the　events　surrounding　Apollo　11's　landing　on　the　Moon　on　July　20；　1969；　my　most　vivid　recollection　is　its　unreal　quality。　Neil　Armstrong　and　Buzz　Aldrin　shuffled　along　the　gray；　dusty　lunar　surface；　the　Earth　looming　large　in　their　sky；　while　Michael　Collins；　now　the　Moon's　own　moon；　orbited　above　them　in　lonely　vigil。　Yes；　it　was　an　astonishing　technological　achievement　and　a　triumph　for　the　United　States。　Yes；　the　astronauts　displayed　death…defying　courage。　Yes；　as　Armstrong　said　as　he　first　alighted；　this　was　a　historic　step　for　the　human　species。　But　if　you　turned　off　the　by…play　between　Mission　Control　and　the　Sea　of　Tranquility；　with　its　deliberately　mundane　and　routine　chatter；　and　stared　into　that　black…and…white　television　monitor；　you　could　glimpse　that　we　humans　had　entered　the　realm　of　myth　and　legend。

We　knew　the　Moon　from　our　earliest　days。　It　was　there　when　our　ancestors　descended　from　the　trees　into　the　savannahs；　when　we　learned　to　walk　upright；　when　we　first　devised　stone　tools；　when　we　domesticated　fire；　when　we　invented　agriculture　and　built　cities　and　set　out　to　subdue　the　Earth。　Folklore　and　popular　songs　celebrate　a　mysterious　connection　between　the　Moon　and　love。　The　word　〃month〃　and　the　second　day　of　the　week　are　both　named　after　the　Moon。　Its　waxing　and　waning—from　crescent　to　full　to　crescent　to　new—was　widely　understood　as　a　celestial　metaphor　of　death　and　rebirth。　It　was　connected　with　the　ovulation　cycle　of　women；　which　has　nearly　the　same　period—as　the　word　〃menstruation〃　（Latin　mensis　=　month；　from　the　word　〃to　measure〃）　reminds　us。　Those　who　sleep　in　moonlight　go　mad；　the　connection　is　preserved　in　the　English　word　〃lunatic。〃　In　the　old　Persian　story；　a　vizier　renowned　for　his　wisdom　is　asked　which　is　more　useful；　the　Sun　or　the　Moon。　〃The　Moon；〃　he　answers；　〃because　the　Sun　shines　in　daytime　when　it's　light　out　anyway。〃　Especially　when　we　lived　out…of…doors；　it　was　a　major—if　oddly　intangible—presence　in　our　lives。

The　Moon　was　a　metaphor　for　the　unattainable：　〃You　plight　as　well　ask　for　the　Moon；〃　they　used　to　say。　Or　〃You　can　no　more　do　that　than　fly　to　the　Moon。〃　For　most　of　our　history；　eve　had　no　idea　what　it　was。　A　spirit？　A　god？　A　thing？　It　didn't　look　like　something　big　far　away；　but　more　like　something　small　nearby—something　the　size　of　a　plate；　maybe；　hanging　in　the　sky　a　little　above　our　heads。　Ancient　Greek　philosophers　debated　the　proposition　〃that　the　Moon　is　exactly　as　large　as　it　looks〃　（betraying　a　hopeless　confusion　between　linear　and　angular　size）。　Walking　on　the　Moon　would　have　seemed　a　screwball　idea；　it　made　more　sense　to　imagine　somehow　climbing　up　into　the　sky　on　a　ladder　or　on　the　back　of　a　giant　bird；　grabbing　the　Moon；　and　bringing　it　down　to　Earth。　Nobody　ever　succeeded；　although　there　were　myths　aplenty　about　heroes　who　had　tried。

Not　until　a　few　centuries　ago　did　the　idea　of　the　Moon　as　a　place；　a　quarter…million　miles　away；　gain　wide　currency。　And　in　that　brief　flicker　of　time；　we've　gone　from　the　earliest　steps　in　understanding　the　Moon's　nature　to　walking　and　joy…riding　on　its　surface。　We　calculated　how　objects　move　in　space；　liquefied　oxygen　from　the　air；　invented　big　rockets；　telemetry；　reliable　electronics；　inertial　guidance；　and　much　else。　Then　we　sailed　out　into　the　sky。

I　was　lucky　enough　to　be　involved　in　the　Apollo　program；　but　I　don't　blame　people　who　think　the　whole　thing　was　faked　in　a　Hollywood　movie　studio。　In　the　late　Roman　Empire；　pagan　philosophers　had　attacked　Christian　doctrine　on　the　ascension　to　Heaven　of　the　body　of　Christ　and　on　the　promised　bodily　resurrection　of　the　dead—because　the　force　of　gravity　pulls　down　all　〃earthly　bodies。〃　St。　Augustine　rejoined：　〃If　human　skill　can　by　some　contrivance　fabricate　vessels　that　float；　out　of　metals　which　sink。　。　。　how　much　more　credible　is　it　that　God；　by　some　hidden　mode　of　operation；　should　even　more　certainly　effect　that　these　earthly　masses　be　emancipated〃　from　the　chains　that　bind　them　to　Earth？　That　humans　should　one　day　discover　such　a　〃mode　of　operation〃　was　beyond　imagining。　Fifteen　hundred　years　later；　we　emancipated　ourselves。

The　achievement　elicited　an　amalgam　of　awe　and　concern。　Some　remembered　the　story　of　the　Tower　of　Babel。　Some；　orthodox　Moslems　among　them；　felt　setting　foot　on　the　Moon's　surface　to　be　impudence　and　sacrilege。　Many　greeted　it　as　a　turning　point　in　history。

The　Moon　is　no　longer　unattainable。　A　dozen　humans；　all　Americans；　have　made　those　odd　bounding　motions　they　called　〃moonwalks〃　on　the　crunchy；　cratered；　ancient　gray　lava—beginning　on　that　July　day　in　1969。　But　since　1972；　no　one　from　any　nation　has　ventured　back。　Indeed；　none　of　us　has　gone　anywhere　since　the　glory　days　of　Apollo　except　into　low　Earth　orbit—like　a　toddler　who　takes　a　few　tentative　steps　outward　and　then；　breathless；　retreats　to　the　safety　of　his　mother's　skirts。

Once　upon　a　time；　we　soared　into　the　Solar　System。　For　a　few　years。　Then　we　hurried　back。　Why？　What　happened？　What　was　Apollo　really　about？

The　scope　and　audacity　of　John　Kennedy's　May　25；　1961　message　to　a　joint　session　of　Congress　on　〃Urgent　National　Needs〃—the　speech　that　launched　the　Apollo　program—dazzled　me。　We　would　use　rockets　not　yet　designed　and　alloys　not　yet　conceived；　navigation　and　docking　schemes　not　yet　devised；　in　order　to　send　a　man　to　an　unknown　world—a　world　not　yet　explored；　not　even　in　a　preliminary　way；　not　even　by　robots—and　we　would　bring　him　safely　back；　and　we　would　do　it　before　the　decade　was　over。　This　confident　pronouncement　was　made　before　any　American　had　even　achieved　Earth　orbit。

As　a　newly　minted　Ph。D。；　I　actually　thought　all　this　had　something　centrally　to　do　with　science。　But　the　President　did　not　talk　about　discovering　the　origin　of　the　Moon；　or　even　about　bringing　samples　of　it　back　for　study。　All　he　seemed　to　be　interested　in　was　sending　someone　there　and　bringing　him　home。　It　was　a　kind　of　gesture。　Kennedy's　science　advisor；　Jerome　Wiesner；　later　told　me　he　had　made　a　deal　with　the　President：　If　Kennedy　would　not　claim　that　Apollo　was　about　science；　then　he。　Wiesner；　would　support　it。　So　if　not　science；　what？

The　Apollo　program　is　really　about　politics；　others　told　me。　This　sounded　more　promising。　Nonaligned　nations　would　be　tempted　to　drift　toward　the　Soviet　Union　if　it　was　ahead　in　space　exploration；　if　the　United　States　showed　insufficient　〃national　vigor。〃　I　didn't　follow。　Here　was　the　United　States；　ahead　of　the　Soviet　Union　in　virtually　every　area　of　technology—the　world's　economic；　military；　and；　on　occasion；　even　moral　leader—and　Indonesia　would　go　munist　because　Yuri　Gagarin　beat　John　Glenn　to　Earth　orbit？　What's　so　special　about　space　technology？　Suddenly　I　understood。

Sending　people　to　orbit　the　Earth　or　robots　to　orbit　the　Sun　requires　rockets—big；　reliable；　powerful　rockets。　Those　same　rockets　can　be　used　for　nuclear　war。　The　same　technolo