▁are ▁the ▁mor aines — the ▁d irt ▁and ▁de br is ▁carried ▁by ▁the ▁gla cier . ▁ ▁The ▁center ▁is ▁h ollow ed ▁out ▁because ▁the ▁ice ▁is ▁mostly ▁gone . ▁▁ ▁These ▁supposed ▁al pine ▁gla ci ers ▁have ▁been ▁called ▁gla cier - like ▁forms ▁( GL F ) ▁or ▁gla cier - like ▁flows ▁( GL F ). ▁▁ ▁Gla cier - like ▁forms ▁are ▁a ▁later ▁and ▁maybe ▁more ▁accurate ▁term ▁because ▁we ▁cannot ▁be ▁sure ▁the ▁structure ▁is ▁currently ▁moving . ▁▁ ▁, ▁ ▁| ▁ ▁Possible ▁ping os ▁The ▁radial ▁and ▁concent ric ▁cra cks ▁visible ▁here ▁are ▁common ▁when ▁forces ▁pen et rate ▁a ▁brit t le ▁layer , ▁such ▁as ▁a ▁rock ▁thrown ▁through ▁a ▁glass ▁window . ▁These ▁particular ▁f ract ures ▁were ▁probably ▁created ▁by ▁something ▁emer ging ▁from ▁below ▁the ▁brit t le ▁Mart ian ▁surface . ▁Ice ▁may ▁have ▁accum ulated ▁under ▁the ▁surface ▁in ▁a ▁l ens ▁shape ; ▁thus ▁making ▁these ▁crack ed ▁m ounds . ▁ ▁Ice ▁being ▁less ▁dense ▁than ▁rock , ▁pushed ▁up wards ▁on ▁the ▁surface ▁and ▁generated ▁these ▁sp ider ▁web - like ▁patterns . ▁A ▁similar ▁process ▁creates ▁similar ▁s ized ▁m ounds ▁in ▁ar ctic ▁t und ra ▁on ▁Earth . ▁ ▁Such ▁features ▁are ▁called ▁" ping os , ", ▁an ▁In uit ▁word . ▁ ▁P ing os ▁would ▁contain ▁pure ▁water ▁ice ; ▁thus ▁they ▁could ▁be ▁sources ▁of ▁water ▁for ▁future ▁colon ists ▁of ▁Mars .