天文学英文版PPT资料 (12)

RogerA.Freedman•WilliamJ.KaufmannIIICHAPTER11Mercury,Venus,MarsUniverseEighthEditionOnlineQuizfromChapter11dueWednesday10/20OnlineQuizfromChapter12,13,14dueMonday10/25(relax,Ch.14isprettyshort).SkipChapter15(“VagabondsoftheSolarSystem”)ExamIInowonWednesday10/27(Ch.7-14).HalfofthelectureperiodMonday10/25willbedevotedtocomprehensivereviewlikelasttime.HWandExamIIWhyisthesurfaceofMercurycoolerthanthesurfaceofVenus?A.MercurymovestoorapidlyaroundtheSuntobeheatedupsignificantly.B.Mercury,unlikeVenus,doesnothaveanatmosphereandthereisnogreenhouseeffect.C.Mercuryisaveryreflectivebody,somostoftheelectromagneticradiationincidentonitisnotabsorbed.D.MercuryismuchsmallerthanVenus.E.Mercury’smagneticfielddeflectssomesolarradiation.Q11.4WhyisthesurfaceofMercurycoolerthanthesurfaceofVenus?A.MercurymovestoorapidlyaroundtheSuntobeheatedupsignificantly.B.Mercury,unlikeVenus,doesnothaveanatmosphereandthereisnogreenhouseeffect.C.Mercuryisaveryreflectivebody,somostoftheelectromagneticradiationincidentonitisnotabsorbed.D.MercuryismuchsmallerthanVenus.E.Mercury’smagneticfielddeflectssomesolarradiation.A11.4ThesurfaceofVenusA.exhibitsplatetectonicactivitysimilartothatseenonEarth.B.exhibitsacrustthathasnotbrokenupintomovingplatesbutdoesexhibithotspotvolcanism.C.isrelativelysmoothandfeatureless.D.exhibitsnotectonicactivityasfaraswecantell.E.hasnotyetbeenstudiedduetothedensecloudcover,sowedonotknowifthereisanytectonicactivity.Q11.7ThesurfaceofVenusA.exhibitsplatetectonicactivitysimilartothatseenonEarth.B.exhibitsacrustthathasnotbrokenupintomovingplatesbutdoesexhibithotspotvolcanism.C.isrelativelysmoothandfeatureless.D.exhibitsnotectonicactivityasfaraswecantell.E.hasnotyetbeenstudiedduetothedensecloudcover,sowedonotknowifthereisanytectonicactivity.A11.7WenowknowthatwaterexistsonMars.ThiswaterisintheformofA.liquidinriversonly.B.atmosphericwatervaporonly.C.undergroundreservoirsofliquidwater.D.iceinpolaricecapsonly.E.permafrost,polaricecaps,andasmallamountofatmosphericvapor.Q11.15WenowknowthatwaterexistsonMars.ThiswaterisintheformofA.liquidinriversonly.B.atmosphericwatervaporonly.C.undergroundreservoirsofliquidwater.D.iceinpolaricecapsonly.E.permafrost,polaricecaps,andasmallamountofatmosphericvapor.A11.15WhichofthefollowinghavenotbeenfoundonMars?A.MovingtectonicplatesB.WispycloudsC.DuststormsD.AncientriverbedsE.AdvancingandrecedingpolaricecapsQ11.13WhichofthefollowinghavenotbeenfoundonMars?A.MovingtectonicplatesB.WispycloudsC.DuststormsD.AncientriverbedsE.AdvancingandrecedingpolaricecapsA11.13KeyIdeasMotionsofMercury,Venus,andMarsintheEarth’sSky:MercuryandVenuscanbeseeninthemorningoreveningskyonly,whileitispossibletoseeMarsatanytimeofnightdependingonitspositioninitsorbit.Attheirgreatesteasternandwesternelongations,Mercuryisonly28°fromtheSunandVenusisonly47°fromtheSun.ThebestEarth-basedviewsofMarsareobtainedatfavorableoppositions,whenMarsissimultaneouslyatoppositionandnearperihelion.KeyIdeasRotationofMercury,Venus,andMars:PoortelescopicviewsofMercury’ssurfaceledtothemistakenimpressionthattheplanetalwayskeepsthesamefacetowardtheSun(1-to-1spin-orbitcoupling).RadioandradarobservationsrevealedthatMercuryinfacthas3-to-2spin-orbitcoupling:Theplanetrotatesonitsaxisthreetimeseverytwoorbits.Venusrotatesslowlyinaretrogradedirection.Itsrotationperiodislongerthanitsorbitalperiod.MarsrotatesatalmostthesamerateastheEarth,anditsrotationaxisistiltedbyalmostthesameangleastheEarth’saxis.KeyIdeasMercury’sSurface,Interior,andMagneticField:TheMercuriansurfaceispockedwithcraters,butthereareextensivesmoothplainsbetweenthesecraters.LongcliffscalledscarpsmeanderacrossthesurfaceofMercury.Theseprobablyformedastheplanet’scrustcooled,solidified,andshrank.Mercuryhasanironcorewithadiameterequaltoabout3⁄4oftheplanet’sdiameter.Bycontrast,thediameteroftheEarth’scoreisonlyslightlymorethan1⁄2ofEarth’sdiameter.Mercuryhasaweakmagneticfield,whichindicatesthatatleastpartoftheironcoreisliquid.KeyIdeasComparingVenusandMars:MostofthesurfaceofVenusisataboutthesameelevation,withjustafewelevatedregions.OnMars,thesouthernhighlandsriseseveralkilometersabovethenorthernlowlands.Venushasathickatmosphereandavolcanicallyactivesurface.Marshasaverythinatmosphereandlittleornocurrentvolcanism.ThereisnoevidenceofplatetectonicsoneitherVenusorMars.OnVenus,thereisvigorousconvectionintheplanet’sinterior,butthecrustistoothintomovearoundinplates;instead,itwrinklesandflakes.OnMars,theplanet’ssmallersizemeansthecrusthascooledandbecometoothicktoundergosubduction.KeyIdeasVolcanoesonbothVenusandMarswereproducedbyhotspotsintheplanet’sinterior.TheentireVenusiansurfaceisabout500millionyearsoldandhasrelativelyfewcraters.Bycontrast,mostoftheMartiansurfaceiscrateredandisprobablybillionsofyearsold.ThesouthernhighlandsonMarsarethemostheavilycrateredandhencetheoldestpartoftheplanet’ssurface.KeyIdeasTheAtmospheresofVenusandMars:Bothplanetaryatmospheresareover95%carbondioxide,withasmallpercentageofnitrogen.ThepressureatthesurfaceofVenusisabout90atmospheres.Thegreenhouseeffectisverystrong,whichraisesthe