水星（英文）mercury

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1、http://www.enchantedlearning.com/subjects/astronomy/planets/MercuryMercury(0.4AU)istheclosestplanettotheSunandthesmallestplanet(0.055Earthmasses).Mercuryhasnonaturalsatellites,anditsonlyknowngeologicalfeaturesbesidesimpactcratersare"wrinkle-ridges",pr

2、obablyproducedbyaperiodofcontractionearlyinitshistory.Mercury'salmostnegligibleatmosphereconsistsofatomsblastedoffitssurfacebythesolarwind.Itsrelativelylargeironcoreandthinmantlehavenotyetbeenadequatelyexplained.Hypothesesincludethatitsouterlayerswere

3、strippedoffbyagiantimpact,andthatitwaspreventedfromfullyaccretingbytheyoungSun'senergy.GENERALINFORMATIONONMERCURYMercuryistheplanetclosesttotheSuninourSolarSystem.Thissmall,rockyplanethasalmostnoatmosphere.Mercuryhasaveryellipticalorbitandahugerangei

4、ntemperature.Duringthelongdaytime(whichlasts58.65EarthdaysoralmostanentireMercurianyear,whichis88dayslong),thetemperatureishotterthananoven;duringthelongnight(thesamelength),thetemperatureiscolderthanafreezer.MercuryissoclosetotheSunthatyoucanonlyseei

5、tnearsunriseorsunset.CratersonthesurfaceofMercury.Mercuryisaheavilycrateredplanet;itssurfaceissimilartothesurfaceofourMoon.CrateringonMercurytriggeredvolcaniceruptionsthatfilledmuchofthesurroundingarea.Mercurydoeshaveamagneticfield(probablygeneratedby

6、apartly-liquidironcore).SIZEMercuryisabout3,031miles(4,878km)indiameter.Itisthesmallestplanetinoursolarsystem(itusedtobeconsideredthesecond-smallestplanet,whenPlutowasstillconsideredtobeaplanet).MercuryisabitoveronethirdofthediameteroftheEarth.Mercury

7、isonlyslightlylargerthantheEarth'smoon.MASSANDGRAVITYMercury'smassisabout3.3x1023kg.Thisisabout1/20thofthemassoftheEarth.ThegravityonMercuryis38%ofthegravityonEarth.A100poundpersonwouldweighonly38poundsonMercury.TocalculateyourweightonMercury,justmult

8、iplyyourweightby0.38(orgotheplanetaryweightcalculator)ATMOSPHEREMercury'sthinatmosphereconsistoftraceamountsofhydrogenandhelium.Theatmosphericpressureisonlyabout1x10-9millibars;thisisatinyfraction(about2trillionths)oftheatmosphericpressureonEa