【Sincepeoplefirstsentrocketsintospaceinthe1950swehavebeenleavingbehindallsortsofthings.Someofthemlikethecamerawerelostbyastronautswhiletheydidworkoutsidetheirspaceship.Butmuchofthespacejunkismade】

　　Sincepeoplefirstsentrocketsintospaceinthe1950swehavebeenleavingbehindallsortsofthings.Someofthemlikethecamerawerelostbyastronautswhiletheydidworkoutsidetheirspaceship.Butmuchofthespacejunkismadeupoflittlepiecesofthingsthatwereoncebiggerobjectsuntiltheystruckeachotherandbrokeapart.

　　Somethingswesendintospacefallbacktowardtheearthandburnupintheatmosphere.Butlargerpiecessometimessurvivetheextremeheatandhitthegroundortheoceanatgreatspeeds.Sothereisalwaysconcernthatsomethingmayfallfromtheskyanddosomeharm.

　　Butspacejunkfallingonhousetops(屋顶)isnotthebiggestworry.Scientistsareconcernedaboutwhathappenswhenanemptyrocketstrikesanotherwhileorbiting(绕轨道飞行)theearth.Twobigthingsbecomemanysmallerthings.Theythenhitotherthings.Thepiecesgetsmallerandsmalleruntiltheyformacloudofjunkthatblocksthepathoffuturespacevehicles.

　　Sowhatcanbedonetocleanupthespacearoundourplanet?MarcoCastronuovoanItalianresearchertalksaboutsendingasatelliteintospacethatwouldgetveryclosetosomeofthelargerpiecesofspacejunk.Thesatellitewouldconnectasmallrockettotheuselessobject.Whentherocketexplodesitpushesthejunkintoalowerandslowerorbitnearertheearth.Afteratimethejunkburnsupintheatmosphere.

　　Mr.Castronuovohasproposed(提议)usinganumberofsmallsatelliteswithroboticarms.Onearmwouldcatchthespacejunkandanotherarmwouldconnecttherocket.Heimaginesthateachsatellitewouldjumpfromonelargepieceofjunktoanother.Hethinksthismethodcoulddestroyabouttenlargeobjectseachyear.

　　Scientistshavebeenconcernedaboutspacejunkformanyyears.Rightnowthecostsoftheclean-uphavebeentoogreat.Mr.Castronuovosayshissystemcouldbeputinplaceforamuchmorereasonableamountofmoney.

　　小题1:Muchofthespacejunk_____.A．wasthrownbytheastronautsB．isfrombrokenspaceshipC．ismadeupofsmallpiecesofthingsD．returnstotheearthpiecebypiece小题2:Scientistsaremostworriedthatthespacejunk_____.A．willstopthefuturespacevehicles