Ice Has Hidden Forms: Ice VII Forms Under Pressure

We think freezing always makes the same ice because we meet only one form at normal pressure. But water can build many crystal orders under pressure. High pressure squeezes molecules into different lattices and creates new phases. Ice VII is a notable dense phase in that family. This matters in planetary science because water inside some worlds can exist as unfamiliar ice. What we call ice can behave like a different material under new conditions. So water is less simple than it looks. Phase diversity shows how many structures nature can build from one molecule.