¡¶pale blue dot -carl sagan¡·

ÏÂÔر¾Êé

Ìí¼ÓÊéÇ©

pale blue dot -carl sagan- µÚ26½Ú


°´¼üÅÌÉÏ·½Ïò¼ü ¡û »ò ¡ú ¿É¿ìËÙÉÏÏ·­Ò³£¬°´¼üÅÌÉ쵀 Enter ¼ü¿É»Øµ½±¾ÊéĿ¼ҳ£¬°´¼üÅÌÉÏ·½Ïò¼ü ¡ü ¿É»Øµ½±¾Ò³¶¥²¿£¡
randa's¡¡interior¡£¡¡Or¡¡perhaps¡¡we¡¡are¡¡seeing¡¡the¡¡results¡¡of¡¡the¡¡primordial¡¡collision¡¡that¡¡is¡¡thought¡¡to¡¡have¡¡knocked¡¡Uranus¡¡over¡£¡¡Or£»¡¡just¡¡conceivably£»¡¡maybe¡¡Miranda¡¡was¡¡once¡¡utterly¡¡destroyed£»¡¡dismembered£»¡¡blasted¡¡into¡¡smithereens¡¡by¡¡a¡¡wild¡¡careening¡¡world£»¡¡with¡¡many¡¡collision¡¡fragments¡¡still¡¡left¡¡in¡¡Miranda's¡¡orbit¡£¡¡The¡¡shards¡¡and¡¡remnants£»¡¡slowly¡¡colliding£»¡¡gravitationally¡¡attracting¡¡one¡¡another£»¡¡may¡¡have¡¡re¡­aggregated¡¡into¡¡just¡¡such¡¡a¡¡jumbled£»¡¡patchy£»¡¡unfinished¡¡world¡¡as¡¡Miranda¡¡is¡¡today¡£

For¡¡me£»¡¡there's¡¡something¡¡eerie¡¡about¡¡the¡¡pictures¡¡of¡¡dusky¡¡Miranda£»¡¡because¡¡I¡¡can¡¡remember¡¡so¡¡well¡¡when¡¡it¡¡¡®vas¡¡only¡¡a¡¡faint¡¡point¡¡of¡¡light¡¡almost¡¡lost¡¡in¡¡the¡¡glare¡¡of¡¡Uranus£»¡¡discovered¡¡through¡¡great¡¡difficulty¡¡by¡¡dint¡¡of¡¡the¡¡astronomer's¡¡skills¡¡and¡¡patience¡£¡¡In¡¡only¡¡half¡¡a¡¡lifetime¡¡it¡¡has¡¡gone¡¡from¡¡an¡¡undiscovered¡¡world¡¡to¡¡a¡¡destination¡¡whose¡¡ancient¡¡and¡¡idiosyncratic¡¡secrets¡¡have¡¡been¡¡at¡¡least¡¡partially¡¡revealed¡£




CHAPTER¡¡9¡¡¡¡¡¡AN¡¡AMERICAN¡¡SHIP¡¡AT¡¡THE¡¡FRONTIERS¡¡OF¡¡THE¡¡SOLAR¡¡SYSTEM

¡¡


¡£¡¡¡£¡¡¡£¡¡by¡¡the¡¡shore¡¡of¡¡Triton's¡¡Lake¡¡¡£¡¡¡£¡¡¡£

I¡¡will¡¡clear¡¡my¡¡breast¡¡of¡¡secrets¡£

¡ªEURIPIDES£»¡¡ION¡¡£¨CA¡£¡¡413¡¡B¡£C¡££©

Neptune¡¡was¡¡the¡¡final¡¡port¡¡of¡¡call¡¡in¡¡Voyager¡¡2's¡¡grand¡¡tour¡¡of¡¡the¡¡Solar¡¡System¡£¡¡Usually£»¡¡it¡¡is¡¡thought¡¡of¡¡as¡¡the¡¡penultimate¡¡planet£»¡¡with¡¡Pluto¡¡the¡¡outermost¡£¡¡But¡¡because¡¡of¡¡Pluto's¡¡stretched¡­out£»¡¡elliptical¡¡orbit£»¡¡Neptune¡¡has¡¡lately¡¡been¡¡the¡¡outermost¡¡planet£»¡¡and¡¡will¡¡remain¡¡so¡¡until¡¡1999¡£¡¡Typical¡¡temperatures¡¡in¡¡its¡¡upper¡¡clouds¡¡are¡¡about¡¡¡­240¡ãC£»¡¡because¡¡it¡¡is¡¡so¡¡far¡¡from¡¡the¡¡warming¡¡rays¡¡of¡¡the¡¡Sun¡£¡¡It¡¡would¡¡be¡¡colder¡¡still¡¡except¡¡for¡¡the¡¡heat¡¡welling¡¡up¡¡from¡¡its¡¡interior¡£¡¡Neptune¡¡glides¡¡along¡¡the¡¡hem¡¡of¡¡interstellar¡¡night¡£¡¡It¡¡is¡¡so¡¡far¡¡away¡¡that£»¡¡in¡¡its¡¡sky£»¡¡the¡¡Sun¡¡appears¡¡as¡¡little¡¡more¡¡than¡¡an¡¡extremely¡¡bright¡¡star¡£

How¡¡far£¿¡¡So¡¡far¡¡away¡¡that¡¡it¡¡has¡¡yet¡¡to¡¡plete¡¡a¡¡single¡¡trip¡¡around¡¡the¡¡Sun£»¡¡a¡¡Neptunian¡¡year£»¡¡since¡¡its¡¡discovery¡¡in¡¡1846¡£*¡¡It's¡¡so¡¡far¡¡away¡¡that¡¡it¡¡cannot¡¡be¡¡seen¡¡with¡¡the¡¡naked¡¡eye¡£¡¡It's¡¡so¡¡far¡¡away¡¡that¡¡it¡¡takes¡¡light¡ªfaster¡¡than¡¡which¡¡nothing¡¡can¡¡go¡ªmore¡¡than¡¡five¡¡hours¡¡to¡¡get¡¡from¡¡Neptune¡¡to¡¡Earth¡£

*¡¡It¡¡takes¡¡so¡¡long¡¡to¡¡circuit¡¡the¡¡Sun¡¡because¡¡its¡¡orbit¡¡is¡¡so¡¡vast£»¡¡23¡¡billion¡¡miles¡¡around£»¡¡and¡¡because¡¡the¡¡force¡¡of¡¡the¡¡Sun's¡¡gravity¡ªwhich¡¡keeps¡¡it¡¡from¡¡flying¡¡out¡¡into¡¡interstellar¡¡space¡ªis¡¡at¡¡that¡¡distant¡¡paratively¡¡feeble£»¡¡less¡¡than¡¡a¡¡thousandth¡¡what¡¡it¡¡is¡¡in¡¡the¡¡Earth's¡¡vicinity¡£

When¡¡Voyager¡¡2¡¡raced¡¡through¡¡the¡¡Neptune¡¡system¡¡in¡¡1989£»¡¡its¡¡cameras£»¡¡spectrometers£»¡¡particle¡¡and¡¡field¡¡detectors£»¡¡and¡¡other¡¡instruments¡¡were¡¡feverishly¡¡examining¡¡the¡¡planet£»¡¡its¡¡moons£»¡¡and¡¡its¡¡rings¡£¡¡The¡¡planet¡¡itself£»¡¡like¡¡its¡¡cousins¡¡Jupiter£»¡¡Saturn£»¡¡and¡¡Uranus£»¡¡is¡¡a¡¡giant¡£¡¡Every¡¡planet¡¡is¡¡an¡¡Earthlike¡¡world¡¡at¡¡heart¡ªbut¡¡the¡¡four¡¡gas¡¡giants¡¡wear¡¡elaborate£»¡¡cumbersome¡¡disguises¡£¡¡Jupiter¡¡and¡¡Saturn¡¡are¡¡great¡¡gas¡¡worlds¡¡with¡¡relatively¡¡small¡¡rocky¡¡and¡¡icy¡¡cores¡£¡¡But¡¡Uranus¡¡and¡¡Neptune¡¡are¡¡fundamentally¡¡rock¡¡and¡¡ice¡¡worlds¡¡swaddled¡¡in¡¡dense¡¡atmospheres¡¡that¡¡hide¡¡them¡¡from¡¡view¡£

Neptune¡¡is¡¡four¡¡times¡¡bigger¡¡than¡¡the¡¡Earth¡£¡¡When¡¡we¡¡look¡¡down¡¡on¡¡its¡¡cool£»¡¡austere¡¡blueness£»¡¡again¡¡we¡¡are¡¡seeing¡¡only¡¡atmosphere¡¡and¡¡clouds¡ªno¡¡solid¡¡surface¡£¡¡Again£»¡¡the¡¡atmosphere¡¡is¡¡made¡¡mainly¡¡of¡¡hydrogen¡¡and¡¡helium£»¡¡with¡¡a¡¡little¡¡methane¡¡and¡¡traces¡¡of¡¡other¡¡hydrocarbons¡£¡¡There¡¡may¡¡also¡¡be¡¡some¡¡nitrogen¡£¡¡The¡¡bright¡¡clouds£»¡¡which¡¡seem¡¡to¡¡be¡¡methane¡¡crystals£»¡¡float¡¡above¡¡thick£»¡¡deeper¡¡clouds¡¡of¡¡unknown¡¡position¡£¡¡From¡¡the¡¡motion¡¡of¡¡the¡¡clouds¡¡we¡¡discovered¡¡fierce¡¡winds£»¡¡approaching¡¡the¡¡local¡¡speed¡¡of¡¡sound¡£¡¡A¡¡Great¡¡Dark¡¡Spot¡¡was¡¡found£»¡¡curiously¡¡at¡¡almost¡¡the¡¡same¡¡latitude¡¡as¡¡the¡¡Great¡¡Red¡¡Spot¡¡on¡¡Jupiter¡£¡¡The¡¡azure¡¡color¡¡seems¡¡appropriate¡¡for¡¡a¡¡planet¡¡named¡¡after¡¡the¡¡god¡¡of¡¡the¡¡sea¡£

Surrounding¡¡this¡¡dimly¡¡lit£»¡¡chilly£»¡¡stormy£»¡¡remote¡¡world¡¡is¡ªhere¡¡also¡ªa¡¡system¡¡of¡¡rings£»¡¡each¡¡posed¡¡of¡¡innumerable¡¡orbiting¡¡objects¡¡ranging¡¡in¡¡size¡¡from¡¡the¡¡fine¡¡particles¡¡in¡¡cigarette¡¡smoke¡¡to¡¡small¡¡trucks¡£¡¡Like¡¡the¡¡rings¡¡of¡¡the¡¡other¡¡Jovian¡¡planets£»¡¡those¡¡of¡¡Neptune¡¡seem¡¡to¡¡be¡¡evanescent¡ªit¡¡is¡¡calculated¡¡that¡¡gravity¡¡and¡¡solar¡¡radiation¡¡will¡¡disrupt¡¡them¡¡in¡¡much¡¡less¡¡than¡¡the¡¡age¡¡of¡¡the¡¡Solar¡¡System¡£¡¡If¡¡they¡¡are¡¡destroyed¡¡quickly£»¡¡we¡¡must¡¡see¡¡them¡¡only¡¡because¡¡they¡¡were¡¡made¡¡recently¡£¡¡But¡¡how¡¡can¡¡rings¡¡be¡¡made£¿

The¡¡biggest¡¡moon¡¡in¡¡the¡¡Neptune¡¡system¡¡is¡¡called¡¡Triton¡£*¡¡Nearly¡¡six¡¡of¡¡our¡¡days¡¡are¡¡required¡¡for¡¡it¡¡to¡¡orbit¡¡Neptune£»¡¡which¡ªalone¡¡among¡¡big¡¡moons¡¡in¡¡the¡¡Solar¡¡System¡ªit¡¡does¡¡in¡¡the¡¡opposite¡¡direction¡¡to¡¡which¡¡its¡¡planet¡¡spins¡¡£¨clockwise¡¡if¡¡we¡¡say¡¡Neptune¡¡rotates¡¡counterclockwise£©¡£¡¡Triton¡¡has¡¡a¡¡nitrogen¡­rich¡¡atmosphere£»¡¡somewhat¡¡similar¡¡to¡¡Titan's£»¡¡but£»¡¡because¡¡the¡¡air¡¡and¡¡haze¡¡are¡¡much¡¡thinner£»¡¡we¡¡can¡¡see¡¡its¡¡surface¡£¡¡The¡¡landscapes¡¡are¡¡varied¡¡and¡¡splendid¡£¡¡This¡¡is¡¡a¡¡world¡¡of¡¡ices¡ªnitrogen¡¡ice£»¡¡methane¡¡ice£»¡¡probably¡¡underlain¡¡by¡¡more¡¡familiar¡¡water¡¡ice¡¡and¡¡rock¡£¡¡There¡¡are¡¡impact¡¡basins£»¡¡which¡¡seem¡¡to¡¡have¡¡been¡¡flooded¡¡with¡¡liquid¡¡before¡¡refreezing¡¡£¨so¡¡there¡¡once¡¡were¡¡lakes¡¡on¡¡Triton£©£»¡¡impact¡¡craters£»¡¡long¡¡crisscrossing¡¡valleys£»¡¡vast¡¡plains¡¡covered¡¡by¡¡freshly¡¡fallen¡¡nitrogen¡¡snow£»¡¡puckered¡¡terrain¡¡that¡¡resembles¡¡the¡¡skin¡¡of¡¡a¡¡cantaloupe£»¡¡and¡¡more¡¡or¡¡less¡¡parallel£»¡¡long£»¡¡dark¡¡streaks¡¡that¡¡seem¡¡to¡¡have¡¡been¡¡blown¡¡by¡¡the¡¡wind¡¡and¡¡then¡¡deposited¡¡on¡¡the¡¡icy¡¡surface¡¡despite¡¡how¡¡sparse¡¡Triton's¡¡atmosphere¡¡is¡¡£¨about¡¡1/10£»000¡¡the¡¡thickness¡¡of¡¡the¡¡Earth's£©¡£

*¡¡Robert¡¡Goddard£»¡¡the¡¡inventor¡¡of¡¡the¡¡modern¡¡liquid¡­fueled¡¡rocket£»¡¡envisioned¡¡a¡¡time¡¡when¡¡expeditions¡¡to¡¡the¡¡stars¡¡would¡¡be¡¡outfitted¡¡on¡¡and¡¡launched¡¡from¡¡Triton¡£¡¡This¡¡was¡¡in¡¡a¡¡1927¡¡afterthought¡¡to¡¡a¡¡1918¡¡handwritten¡¡manuscript¡¡called¡¡¡¨The¡¡Last¡¡Migration¡£¡¨¡¡Considered¡¡much¡¡too¡¡daring¡¡for¡¡publication£»¡¡it¡¡was¡¡deposited¡¡in¡¡a¡¡friend's¡¡safe¡£¡¡The¡¡cover¡¡page¡¡bears¡¡a¡¡warning£º¡¡¡¨The£§se£§¡¡notes¡¡should¡¡be¡¡read¡¡thoroughly¡¡only¡¡by¡¡an¡¡optimist¡£¡¨

All¡¡the¡¡craters¡¡on¡¡Triton¡¡are¡¡pristine¡ªas¡¡if¡¡stamped¡¡out¡¡by¡¡some¡¡vast¡¡milling¡¡device¡£¡¡There¡¡are¡¡no¡¡slumped¡¡walls¡¡or¡¡muted¡¡relief¡£¡¡Even¡¡with¡¡the¡¡periodic¡¡falling¡¡and¡¡evaporation¡¡of¡¡snow£»¡¡it¡¡seems¡¡that¡¡nothing¡¡has¡¡eroded¡¡the¡¡surface¡¡of¡¡Triton¡¡in¡¡billions¡¡of¡¡years¡£¡¡So¡¡the¡¡craters¡¡that¡¡were¡¡gouged¡¡out¡¡during¡¡the¡¡formation¡¡of¡¡Triton¡¡must¡¡have¡¡all¡¡been¡¡filled¡¡in¡¡and¡¡covered¡¡over¡¡by¡¡some¡¡early¡¡global¡¡resurfacing¡¡event¡£¡¡Triton¡¡orbits¡¡Neptune¡¡in¡¡the¡¡opposite¡¡direction¡¡to¡¡Neptune's¡¡rotation¡ªunlike¡¡the¡¡situation¡¡with¡¡the¡¡Earth¡¡and¡¡its¡¡moon£»¡¡and¡¡with¡¡most¡¡of¡¡the¡¡large¡¡moons¡¡in¡¡the¡¡Solar¡¡System¡£¡¡If¡¡Triton¡¡had¡¡formed¡¡out¡¡of¡¡the¡¡same¡¡spinning¡¡disk¡¡that¡¡made¡¡Neptune£»¡¡it¡¡ought¡¡to¡¡be¡¡going¡¡around¡¡Neptune¡¡in¡¡the¡¡same¡¡direction¡¡that¡¡Neptune¡¡rotates¡£¡¡So¡¡Triton¡¡was¡¡not¡¡made¡¡from¡¡the¡¡original¡¡local¡¡nebula¡¡around¡¡Neptune£»¡¡but¡¡arose¡¡somewhere¡¡else¡ªperhaps¡¡far¡¡beyond¡¡Pluto¡ªand¡¡was¡¡by¡¡chance¡¡gravitationally¡¡captured¡¡when¡¡it¡¡passed¡¡too¡¡close¡¡to¡¡Neptune¡£¡¡This¡¡event¡¡should¡¡have¡¡raised¡¡enormous¡¡solid¡­body¡¡tides¡¡in¡¡Triton£»¡¡melting¡¡the¡¡surface¡¡and¡¡sweeping¡¡away¡¡all¡¡the¡¡past¡¡topography¡£

In¡¡some¡¡places¡¡the¡¡surface¡¡is¡¡as¡¡bright¡¡and¡¡white¡¡as¡¡freshly¡¡fallen¡¡Antarctic¡¡snows¡¡£¨and¡¡may¡¡offer¡¡a¡¡skiing¡¡experience¡¡unrivaled¡¡in¡¡all¡¡the¡¡Solar¡¡System£©¡£¡¡Elsewhere¡¡there's¡¡a¡¡tint£»¡¡ranging¡¡from¡¡pink¡¡to¡¡brown¡£¡¡One¡¡possible¡¡explanation£º¡¡Freshly¡¡fallen¡¡snows¡¡of¡¡nitrogen£»¡¡methane£»¡¡and¡¡other¡¡hydrocarbons¡¡are¡¡irradiated¡¡by¡¡solar¡¡ultraviolet¡¡light¡¡and¡¡by¡¡electrons¡¡trapped¡¡in¡¡the¡¡magnetic¡¡field¡¡of¡¡Neptune£»¡¡through¡¡which¡¡Triton¡¡plows¡£¡¡We¡¡know¡¡that¡¡such¡¡irradiation¡¡will¡¡convert¡¡the¡¡snows¡¡£¨like¡¡the¡¡corresponding¡¡gases£©¡¡to¡¡plex£»¡¡dark£»¡¡reddish¡¡organic¡¡sediments£»¡¡ice¡¡tholins¡ªnothing¡¡alive£»¡¡but¡¡here¡¡too¡¡posed¡¡of¡¡some¡¡of¡¡the¡¡molecules¡¡implicated¡¡in¡¡the¡¡origin¡¡of¡¡life¡¡on¡¡Earth¡¡four¡¡billion¡¡years¡¡ago¡£

In¡¡local¡¡winter£»¡¡layers¡¡of¡¡ice¡¡and¡¡snow¡¡build¡¡up¡¡on¡¡the¡¡surface¡£¡¡£¨Our¡¡winters£»¡¡mercifully£»¡¡are¡¡only¡¡4¡¡percent¡¡as¡¡long¡££©¡¡Through¡¡the¡¡spring£»¡¡they¡¡are¡¡slowly¡¡transformed£»¡¡more¡¡and¡¡more¡¡reddish¡¡organic¡¡molecules¡¡accumulating¡£¡¡By¡¡summertime£»¡¡the¡¡ice¡¡and¡¡snow¡¡have¡¡evaporated£»¡¡the¡¡gases¡¡so¡¡released¡¡migrate¡¡halfway¡¡across¡¡the¡¡planet¡¡to¡¡the¡¡winter¡¡hemisphere¡¡and¡¡there¡¡cover¡¡the¡¡surface¡¡with¡¡ice¡¡and¡¡snow¡¡again¡£¡¡But¡¡the¡¡reddish¡¡organic¡¡molecules¡¡do¡¡not¡¡vaporize¡¡and¡¡are¡¡not¡¡transported¡ªa¡¡lag¡¡deposit£»¡¡they¡¡are¡¡next¡¡winter¡¡covered¡¡over¡¡by¡¡new¡¡snows£»¡¡which¡¡are¡¡in¡¡turn¡¡irradiated£»¡¡and¡¡by¡¡the¡¡following¡¡summer¡¡the¡¡accumulation¡¡is¡¡thicker¡£¡¡As¡¡time¡¡goes¡¡on£»¡¡substantial¡¡amounts¡¡of¡¡organic¡¡matter¡¡are¡¡built¡¡up¡¡on¡¡the¡¡surface¡¡of¡¡Triton£»¡¡which¡¡may¡¡account¡¡for¡¡its¡¡delicate¡¡color¡¡markings¡£

The¡¡streaks¡¡begin¡¡in¡¡small£»¡¡dark¡¡source¡¡regions£»¡¡perhaps¡¡wh
СÌáʾ£º°´ »Ø³µ [Enter] ¼ü ·µ»ØÊéÄ¿£¬°´ ¡û ¼ü ·µ»ØÉÏÒ»Ò³£¬ °´ ¡ú ¼ü ½øÈëÏÂÒ»Ò³¡£ ÔÞһϠÌí¼ÓÊéÇ©¼ÓÈëÊé¼Ü