ICE VII
An exotic type of ice
When water freezes on Earth, it usually forms ordinary water ice known as ice I. But that’s not the only type of ice. Under extreme temperatures and pressures, hydrogen and oxygen can bond in more complex structures, creating over a dozen exotic phases of ice.
In the lab, ice VII can be formed at room temperature, providing that it is exposed to 30,000 times more pressure than we experience on the surface of the Earth. Instead of forming hexagons, ice VII grows as tiny rod-like needles merging into crystal cubes. Scientists tried to imagine environments that paired both high pressure and low temperature where ice VII might form in nature. While theorised to form Jupiter’s frozen ocean moon Europa, or distant watery exoplanets like Gliese 436 b and Gliese 1214 b, naturally-occurring ice VII was first discovered here on Earth within a diamond. Diamonds can incorporate bubbles of fluid as they grow, trapping substances within their crystal structure. As a diamond is so strong, it keeps those inclusions locked within a crystal cage of high pressure, even if it erupts onto the Earth’s surface and cools down.