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		| Paper: | 
		Liquid Water on Frozen Extrasolar Planets? | 
	 
	
		| Volume: | 
		398, Extreme Solar Systems | 
	 
	
		| Page: | 
		537 | 
	 
	
		| Authors: | 
		Ehrenreich, D.; Lecavelier des Etangs, A.; Beaulieu, J.; Grasset, O. | 
	 
	
	
		| Abstract: | 
		The detection of OGLE-2005-BLG-390Lb (Beaulieu et al. 2006) around an M star in the Galactic Bulge unveils the existence of cold (∼ 40 K) Earth-mass planets (Ehrenreich and Cassan 2007). Such planets could nevertheless host liquid water beneath a frozen surface, because of a strong radiogenic heating of the ice shell (Ehrenreich et al. 2006). Heating and cooling of the ice shell depend on the ice-to-rock ratio (I/R) and the age of the planet planet. OGLE 390Lb now seems too old (∼ 10 Gyr) to host a subsurface ocean, for any tested I/R value. However, the heat production rate was larger in the past so that liquid water did flow for several billions of years underneath the ice shell. | 
	 
	
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