Heat flows through the ice lithosphere of Europa

Abstract

Someo f the geologicafle atureso n the surfaceo f Europa'si ce shells uggestth e existenceo f a brittlel ithosphereth ati n somer egionsis no moret han2 km thick.T he surfaceh eatf low neededt o put the brittle-ductiletr ansitionin ice at a deptho f 2 km is at -9 least• -100m W m -, muchh ighert hanp redictedb y tidal heatingm odelsf or a purely conductiviec e shell.A possiblee xplanationlie si n thep robablee xistenceo f a convective layerb eneathth eb rittlel ithospherew, hich,o wingt o tidald issipatioinn warmi ce,c ould contributteo higherh eatf lows.I f a convectives ubsurfaclea yera ndg rains ized ependent flow behavioor f ice area dmittedt,h eg rains izea t brittle-ductilter ansitiond epthc annotb e >1 mm, whichi s consistenwt ith ther equiredv aluef or the onseto f convectionin an ice shell thinner than 20 km.