▁past ▁the ▁planet ▁Mars ▁possessed ▁bodies ▁of ▁liquid ▁water ▁on ▁the ▁surface . ▁For ▁a ▁brief ▁period ▁in ▁Mars ' ▁history , ▁it ▁may ▁have ▁also ▁been ▁capable ▁of ▁forming ▁life . ▁At ▁present ▁though , ▁most ▁of ▁the ▁water ▁remaining ▁on ▁Mars ▁is ▁fro zen . ▁If ▁life ▁exists ▁at ▁all ▁on ▁Mars , ▁it ▁is ▁most ▁likely ▁to ▁be ▁located ▁under ground ▁where ▁liquid ▁water ▁can ▁still ▁exist . ▁ ▁Cond itions ▁on ▁the ▁other ▁terrest rial ▁plan ets , ▁Mercur y ▁and ▁Ven us , ▁appear ▁to ▁be ▁too ▁har sh ▁to ▁support ▁life ▁as ▁we ▁know ▁it . ▁But ▁it ▁has ▁been ▁conject ured ▁that ▁Europa , ▁the ▁fourth - larg est ▁moon ▁of ▁Jup iter , ▁may ▁possess ▁a ▁sub - sur face ▁ocean ▁of ▁liquid ▁water ▁and ▁could ▁potentially ▁host ▁life . ▁ ▁Astronom ers ▁have ▁started ▁to ▁discover ▁ex tras olar ▁Earth ▁anal ogs ▁– ▁plan ets ▁that ▁lie ▁in ▁the ▁habit able ▁zone ▁of ▁space ▁surrounding ▁a ▁star , ▁and ▁therefore ▁could ▁possibly ▁host ▁life ▁as ▁we ▁know ▁it . ▁ ▁See ▁also ▁▁ ▁Force ▁of ▁nature ▁ ▁Human ▁nature ▁ ▁Natural ▁history ▁ ▁Natural ism ▁ ▁Natural ▁landscape ▁ ▁Natural ▁law ▁ ▁Natural ▁resource ▁ ▁Natural ▁science ▁ ▁Natural ▁the ology ▁ ▁Nature ▁reserve ▁ ▁Nature ▁tim eline ▁ ▁Nature ▁versus ▁n urt ure ▁ ▁Nature ▁worship ▁ ▁Natur ism ▁ ▁R ew ild ing ▁ ▁Media : ▁ ▁Natural ▁History , ▁by ▁Pl iny ▁the ▁E lder ▁ ▁Nature , ▁by ▁Ralph ▁Wal