ated , ▁leaving ▁the ▁plan ets ▁in ▁their ▁current ▁or bits . ▁ ▁The ▁giant ▁plan ets ▁( J up iter , ▁Sat urn , ▁U ran us , ▁and ▁Ne pt une ) ▁formed ▁further ▁out , ▁beyond ▁the ▁fro st ▁line , ▁which ▁is ▁the ▁point ▁between ▁the ▁or bits ▁of ▁Mars ▁and ▁Jup iter ▁where ▁the ▁material ▁is ▁cool ▁enough ▁for ▁vol atile ▁ icy ▁comp ounds ▁to ▁remain ▁solid . ▁The ▁ ices ▁that ▁formed ▁the ▁J ov ian ▁plan ets ▁were ▁more ▁abund ant ▁than ▁the ▁met als ▁and ▁sil ic ates ▁that ▁formed ▁the ▁terrest rial ▁plan ets , ▁allowing ▁the ▁giant ▁plan ets ▁to ▁grow ▁massive ▁enough ▁to ▁capture ▁hydro gen ▁and ▁hel ium , ▁the ▁light est ▁and ▁most ▁abund ant ▁elements . ▁Plan etes im als ▁beyond ▁the ▁fro st ▁line ▁accum ulated ▁up ▁to ▁ ▁within ▁about ▁ 3   mill ion ▁years . ▁Today , ▁the ▁four ▁giant ▁plan ets ▁compr ise ▁just ▁under ▁ 9 9 % ▁of ▁all ▁the ▁mass ▁orbit ing ▁the ▁Sun . ▁The or ists ▁believe ▁it ▁is ▁no ▁accident ▁that ▁Jup iter ▁lies ▁just ▁beyond ▁the ▁fro st ▁line . ▁Because ▁the ▁fro st ▁line ▁accum ulated ▁large ▁amounts ▁of ▁water ▁via ▁ev ap oration ▁from ▁inf alling ▁ icy ▁material , ▁it ▁created ▁a ▁region ▁of ▁lower ▁pressure ▁that ▁increased ▁the ▁speed ▁of ▁orbit ing ▁dust ▁particles ▁and ▁halt ed ▁their ▁motion ▁toward ▁the ▁Sun . ▁In ▁effect , ▁the ▁fro st ▁line ▁acted ▁as