How high-pressure ices on large ocean worlds can support habitability: The compatibility of amino acids into ice VI and VII

Water oceans in large icy moons and exoplanets are isolated from the rocky interior by thick layers of high-pressure ice, which hinder the direct release of nutrients and organics derived from water-rock interaction to the ocean. Possible uptake of these bio-essential compounds into high-pressure ice phases could regulate their availability in the ocean, but this process is poorly constrained. Here, we measured partition coefficients of glycine and alanine into ices VI and VII under elevated temperature-pressure conditions using a diamond-anvil cell. We observed moderate compatibility of glycine and alanine with partition coefficients: K _{p ,glycine}  = 0.14 and 0.40 in ices VI and VII, respectively; K _{p ,alanine}  = 0.21 and 0.35 in ices VI and VII, respectively. First-principles calculations suggested that amino acids could be incorporated into high-pressure ice’s lattice via cogrowth. Compatibility of amino acids into high-pressure ices would favor their transport in large extraterrestrial oceans, opening an avenue to habitability.