Evidence of stable liquid water oceans beneath the ice crust of moons within the Solar System is of great interest for astrobiology. In particular, subglacial oceans may present hydrothermal processes in their abysses, similarly to terrestrial hydrothermal vents. Therefore, terrestrial extremophilic deep life can be considered a model for putative icy moon extraterrestrial life. However, the comparison between putative extraterrestrial abysses and their terrestrial counterparts suffers from a potentially determinant difference. Indeed, some icy moons oceans may be so deep that the hydrostatic pressure would exceed the maximal pressure at which hydrothermal vent organisms have been isolated. While terrestrial microorganisms that are able to survive in such conditions are known, the effect of high pressure on fundamental biochemical processes is still unclear. In this study, the effects of high hydrostatic pressure on DNA synthesis catalyzed by DNA polymerases are investigated for the first time. The effect on both strand displacement and primer extension activities is measured, and pressure tolerance is compared between enzymes of various thermophilic organisms isolated at different depths.

On the basis of results from exhaustive first-principles simulations, we report a thorough description of the recently identified high pressure phase of the CO2 hydrate, and provide an estimation of the transition pressure from the sI low pressure phase to the C-0 high pressure (HP) phase around 0.6 GPa. The vibrational properties calculated here for the first time might be useful to detect this HP structure in extraterrestrial environments, such as the Jupiter ice moons. Interestingly, we also find that CO2 gas molecules are quasi-free to diffuse along the helical channels of the structure, thus allowing the interchange of volatiles across a solid icy barrier. Taking into account its density and comparing it with other substances, we can estimate the naturally occurring zone of this CO2@H2O HP phase within a giant ice moon such as Ganymede. Other potential planetary implications that all of the found properties of this hydrate might have are also discussed.