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1、AWorldofDifferenceHarryTurtledoveTothememoryofmyfather-in-lawFrankFrankos...andforBarneytheFrog.Author'sNoteMarsisboring.Turnsoutit'stoodamnsmall.Butwhatifitweren't...MINERVAisthefourthplanetoutfromthesuninthesolarsystem,thefirstplanetpastEarth~orbit.At
2、itsnearestapproachtoEarth,Minervaisthebrightestobjectintheskyexceptforthesunandmoon.Itthenlookstothenakedeyelikeabrilliant,gray-bluestarofmagnitude-5.9.Sometimesitmayevenex-ceedthatbrightnessforashortperiod.Thisistheresultofthefamous"Minervanflash,"whic
3、hoccurswhenbreaksinthecloudcoverabovetheplanet~surfaceallowthesuntoreflectdirectlyofficeorwater.Longbeforethecauseofthephenom-enonwasknown,itgavetheplanetitsname:theGreekscalleditAthena,aftertheirfiashing-eyedgoddessofwisdom.MinervaistheLatinnameforthes
4、amedivinity.Sincetheinventionofthetelescope,Minervahasfascinatedobservers.ItistheonlyworminthesolarsystembesidesEarthwherewatercanexistasaliquid,andthepresenceofoxygeninitsatmospherehaslongsuggestedthat,likeEarth,itisahomeforlife.Since1965,AmericanandSo
5、vietspaceprobeshavegreatlyaddedtoourknowledgeofMinerva.Despitetheplanet~thick,cloudyatmosphere,wenowhavereliablemapsofalmostitsentiresurface.Notuntil1976,though,didtheVikingIspace-craftactuallylandontheplanet.TheVikinganalyzedMiner-va~loweratmosphere,an
6、dthecraft'sbiologicalexperimentpackageandthephotographsitreturnedtoEarthconfirmedthatthereislifeontheplanet.VikingI~lastphotograph,arguablythemostfamousevertaken,confirmedfarmorethanthat.Itprovedhumanityisnotaloneintheuniverse,foritshowsaMinervannativec
7、arryingwhatcannotbeanythingbutadeliberatelymanufacturedarti-fact-whetheraweaponorsimplyapoleremainsthesubjectofhotdebate.TransmissionfromVikingIceasedimmediatelyafterthisphotographwasmade...RHarryTurtledoveTABLEDFMINERVANDATAEquatorialdiameter:9,264mile
8、s(14,909kin)Mass:8.35x1024kg(about1.4timesthatofEarth)Density:4.81g/cn?(about87%thatofEarth)Surfacegravity:1.02thatofEarthEscapevelocity:7.60miles/second(12.22km/sec)Greatestdistancefromsun:154,800,000miles(249,120,000km)Leastdis
