The Extended Habitable Epoch of the Universe for Liquids Other than Water

Abstract

At high redshifts, the temperature of the cosmic microwave background (CMB) was higher than its value today. We explore the possibility that life may have arisen early because the higher CMB temperature would have supplied the requisite energy for the existence of different solvents on the surfaces of objects. At redshifts of $z \lesssim 70$, after the first stars are predicted to have formed, a number of molecules (but not water) might have existed in liquid form over intervals of $\sim 10$ Myr to $\sim 100$ Myr. We delineate the challenges and prospects for life in the high-redshift Universe, and assess the various candidates for alternative biochemistries in this context -- of the options considered herein, we conclude that ethane is probably the most promising contender.