I'm trying to design an artificial microbe that could survive in the crust of icy moons and dwarf planets in the outer solar system, such as Pluto and Triton. I'm thinking of making them hydrogen-consuming methanogens, and basing them off azotosomes, artifical cells created out of nitrogen, hydrogen and carbon, with a liquid methane solvent. Technically speaking, all the necessary ingredients are there, locked within nitrogen ice, water ice and carbon dioxide ice, but of course the difficulty is in accessing them. They're frozen solid for one thing, but even then, separating hydrogen from H20 is notoriously energy intensive, and you'd probably end up with a net energy loss. How can I get around this?
The only thing that's come to mind is the possibility of radiolysis, but other than eking trace radioactive elements out of the ice from ancient meteor impacts, I can't figure out how to generate that kind of radioactivity, and that's probably far too inefficient. This is intended to be an artificial species seeded by advanced precursors, btw, so it doesn't matter if any solutions are unlikely to have evolved naturally.
Can anyone help me with this?