▁ 2 0 0 1 ▁updates , ▁the ▁LE O ▁environment ▁in ▁the ▁ ▁alt itude ▁range ▁should ▁be ▁cas c ading . ▁However , ▁only ▁one ▁major ▁satellite ▁collision ▁incident ▁has ▁occurred : ▁the ▁ 2 0 0 9 ▁satellite ▁collision ▁between ▁I rid ium ▁ 3 3 ▁and ▁Cos mos ▁ 2 2 5 1 . ▁The ▁lack ▁of ▁obvious ▁short - term ▁cas c ading ▁has ▁led ▁to ▁spec ulation ▁that ▁the ▁original ▁estimates ▁over st ated ▁the ▁problem . ▁According ▁to ▁K ess ler ▁in ▁ 2 0 1 0 ▁however , ▁a ▁cas cade ▁may ▁not ▁be ▁obvious ▁until ▁it ▁is ▁well ▁advanced , ▁which ▁might ▁take ▁years . ▁ ▁On ▁Earth ▁▁ ▁Although ▁most ▁de br is ▁burn s ▁up ▁in ▁the ▁atmosphere , ▁larger ▁de br is ▁objects ▁can ▁reach ▁the ▁ground ▁int act . ▁According ▁to ▁NASA , ▁an ▁average ▁of ▁one ▁catalog ed ▁piece ▁of ▁de br is ▁has ▁fallen ▁back ▁to ▁Earth ▁each ▁day ▁for ▁the ▁past ▁ 5 0 ▁years . ▁Despite ▁their ▁size , ▁there ▁has ▁been ▁no ▁significant ▁property ▁damage ▁from ▁the ▁de br is . ▁ ▁Notable ▁examples ▁of ▁space ▁j unk ▁falling ▁to ▁Earth ▁and ▁impact ing ▁human ▁life ▁include : ▁▁▁ 1 9 6 9 : ▁five ▁sail ors ▁on ▁a ▁Japanese ▁ship ▁were ▁injured ▁by ▁space ▁de br is . ▁▁▁ 1 9 9 7 : ▁an ▁Oklahoma ▁woman , ▁L ott ie ▁Williams , ▁was ▁injured ▁when ▁she ▁was ▁hit ▁in ▁the ▁shoulder ▁by ▁a