▁period ▁of ▁time . ▁Much ▁of ▁its ▁surface ▁is ▁probably ▁covered ▁by ▁a ▁relatively ▁thick ▁reg ol ith ▁of ▁re work ed ▁impact ▁bre c cias . ▁ ▁The ▁cr ater ed ▁pla ins ▁material ▁is ▁relatively ▁flat ▁with ▁broad ▁rid ges ▁and ▁lo b ate ▁scar ps ▁that ▁in ▁places ▁res emble ▁those ▁of ▁some ▁of ▁the ▁lun ar ▁mar ia . ▁It ▁is ▁difficult ▁to ▁obtain ▁reliable ▁cr ater ▁counts ▁on ▁this ▁unit ▁because ▁many ▁secondary ▁cr aters ▁cannot ▁be ▁distinguished ▁from ▁primary ▁cr aters . ▁Cr ater ed ▁pla ins ▁materials ▁emb ay ▁cr aters ▁in ▁classes ▁c 1 ▁to ▁c 3 ; ▁they ▁may ▁represent ▁la va ▁flows ▁extr ud ed ▁after ▁an ▁initial ▁phase ▁of imp act ▁flux . ▁The ▁al bed o ▁of ▁the ▁cr ater ed ▁pla ins ▁is ▁intermediate ▁compared ▁to ▁that ▁of ▁other ▁mer cur ian ▁units , ▁but ▁higher ▁than ▁that ▁of ▁the ▁lun ar ▁mar ia , ▁and ▁may ▁reflect ▁lower ▁iron ▁and ▁tit an ium ▁content . ▁ ▁The ▁young est ▁rock ▁units ▁consist ▁of ▁rough ▁terra ▁and ▁smooth ▁pla ins ▁materials . ▁R ough ▁terra ▁occurs ▁as ▁over la pping ▁and ▁inter m ixed ▁e ject a ▁blank ets ▁around ▁dust ers ▁of ▁large ▁young ▁cr aters ▁in ▁the ▁eastern ▁part ▁of ▁the ▁quad rangle . ▁The ▁relief ▁here ▁appears ▁to ▁be ▁higher ▁than ▁elsewhere ▁in ▁the ▁map ▁area , ▁and ▁the ▁occurrence ▁of ▁dense ▁arrays ▁of ▁fresh ▁secondary ▁cr aters ▁produces ▁a ▁co ars ely ▁text ured , ▁hum