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《【托福听力备考】tpo13 听力文本——lecture 4》由会员上传分享，免费在线阅读，更多相关内容在应用文档-天天文库。
1、【托福听力备考】TPO13听力文本——Lecture4众所周知，托福TPO材料是备考托福听力最好的材料。相信众多备考托福的同学也一直在练习这套材料，那么在以下内容中我们就为大家带来托福TPO听力练习的文本，希望能为大家的备考带来帮助。TPO13Lecture4AstronomyNarrator:Listentopartofalectureinanastronomyclass.Professor:OK,Iwannagooverthedifferenttypesofmeteorites,andwhatwe’velearnedfromthemabouttheformationofEar
2、th,andthesolarsystem.Uh…thethingiswhat’sespeciallyinterestingaboutmeteoritesisthattheycomefrominterplanetaryspace,buttheyconsistofthesamechemicalelementsthatareinmatteroriginatingonEarth,justindifferentproportions.Butthatmakesiteasiertoidentifysomethingasameteorite,asopposedto…tojustaterrestr
3、ialrock.Sototalkaboutwheremeteoritescomefrom,weneedtotalkaboutcometsandasteroids,whichbasically...they’rebasicallymadeupofdebrisleftoverfromtheoriginofthesolarsystem4.6billionyearsago.NowI’mgoingabitoutofaorderhere…um…I’mnotgoingtogointoanydepthoncometsandasteroidsnow,butwe’llcomebacklaterand
4、dothat.Fornow,I’lljustcoversomebasicinfoaboutthem.OK,cometsandasteroids.Itmighthelpifyouthinkof...rememberwetalkedaboutthetwoclassesofplanetsinoursolarsystem?Andhowtheydifferincomposition?Theterrestrialplanets--likeMarsandEarth--composedlargelyofrocksandmetals,andthelargegasgiants,likeJupiter
5、.Well,thesolarsystemalsohastwoanalogousclassesofobjects,smallerthanplanets--namely,asteroidsandcomets.Relativelynearthesun,intheinnersolarsystem,betweenJupiterandMarstobeprecise,we’vegottheasteroidbelt,whichcontainsabout90percentsofallasteroidsorbitingthesun.Theseasteroidsare…uh…liketheterres
6、trialplanets,inthatthey’recomposedmostlyofrockymaterialandmetals.Farfromthesun,intheoutersolarsystem,beyondJupiter’sorbit,temperaturesarelowenoughtopermiticestoformoutofwaterand…andoutofgaseslikemethaneandcarbondioxide.Loosecollectionsoftheseicesandsmallrockyparticlesformintocomets.Socometsar
7、esimilarincompositiontothegasgiants.Bothcometsandasteroidsare...typicallyaresmallerthanplanets.Anevensmallertypeofinterplanetarydebrisisthemeteoroid.Andit’sfrommeteoroidsthatwegetmeteorsandmeteorites.“Roids”are,forthemostpartanyway,theyarejus
