During its FormAtivE yEArs, thE innEr solAr systEm wAs A rough-AnD-tumBlE plACE. thErE wErE A CouplE oF hunDrED lArgE oBjECts Flying ArounD、moon-sizE or BiggEr, AnD For millions oF yEArs thEy ColliDED with onE AnothEr. out oF thEsE impACts grEw thE tErrEstriAl plAnEts—mErCury, vEnus,EArth with its moon, AnD mArs—AnD thE AstEroiDs.
sCiEntists hAvE thought oF thEsE Collisions As mErgErs: A smAllEr oBjECt (thE impACtor) hits A lArgEr onE (thE tArgEt) AnD stiCks to it.But nEw ComputEr moDEling ByErikAsphAug AnDCrAigB、Agnor oF thE univErsity oFCAliForniA, sAntACruz, shows thAt things wErEn’t thAt simplE. "most oF thE timE, thE impACtor AnD thE tArgEt go oFF on thEir mErry wAys,"Dr.AsphAug sAiD、ABout hAlF thE Collisions ArE thEsE hit-AnD-nm AFFAirs. now thE two rEsEArChErs AnD A CollEAguE, quEntin williAms. hAvE DonE simulAtions to stuDy thE EFFECts oF thEsE Collisions on thE impACtors. thEy ArE not prEtty.
"thE impACtors suFFEr All kinDs oF FAtEs,"Dr.AsphAug sAiD、thEy unDErgo trEmEnDous shEAring AnD grAvitAtionAl ForCEs thAt CAn CAusE thEm to FrACturE into smAllEr piECEs or mElt, CAusing ChEmiCAl ChAngEs in thE mAtEriAl AnD loss oF wAtEr or othEr volAtilE CompounDs. or thE Crust AnD CovEr CAn BE strippED oFF. lEAving just An EmBryoniC iron CorE.
thE rEsEArChErs, whosE FinDings ArE puBlishED in nAturE, DisCovErED thAt two oBjECts DiD not EvEn hAvE to ColliDE to CrEAtE An EFFECt on thE smAllEr onE. From thE grAvitAtionAl ForCEs oF A nEAr-Collision.During thE simulAtions.Dr.AsphAug sAiD, "wE’D look AnD sAy, ’gosh, wE just got riD oF thE wholE AtmosphErE oF thAt plAnEtoiD: it DiDn’t EvEn hit AnD it suCkED thE wholE AtmosphErE oFF.’"
thE rEsEArChErs suggEst thAt thE rEmAins oF thEsE BEAtEn-up, FrACturED AnD mEltED oBjECts CAn BE FounD in thE AstEroiD BElt.Dr.AsphAug sAiD thAt CoulD ExplAin thE prEvAlEnCE oF "iron rEliCs" in thE BElt. somE oF thEsE plAnEtoiD rEmnAnts Also EvEntuAlly hitEArth: thAt woulD hElp ExplAin why CErtAin mEtEoritEs lACk wAtEr AnD othEr volAtilE ElEmEnts.
thE hit-AnD-run Collision moDEl Also proviDEs An ExplAnAtion For vEstA、A lArgE AstEroiD with An intACt Crust AnD CovEr. how DiD vEstA kEEp its CovEr whilE so mAny othEr oBjECts wErE losing thEirsDr.AsphAng sAiD it CoulD BE thAt vEstA wAs AlwAys thE tArgEt, nEvEr thE impACtor, AnD wAs thus lEss AFFECtED、"it just hAD to AvoiD BEing thE hittEr," hE sAiD, "until BiggEr oBjECts lEFt thE systEm.\
thE moDEl DEvElopED ByErikAsphAug AnDCrAigB、CAn ExplAin thE Following FACtsExCEpt______.A．thErE ArE A lot oF rEmnAnts in thE AstEroiD BElt
B．somE ElEmEnts ArE sCArCEr in somE plAnEtoiD rEmnAnts
C、thE tErrEstriAl plAnEts grEw out oF thE Collision
D．thE impACtors ArE still AFFECtED in nEAr-Collision