Number 262 (Story #3), March 14, 1996 by Phillip F. Schewe and Ben Stein A NEW FORM OF ICE has been predicted to form at high pressures. Ice has more solid forms than any other simple substance, with 10 known crystalline structures. Using molecular dynamics simulations, a German-French-Italian team has now predicted that "Ice XI" forms between 3 and 4 Megabars of pressure at room temperature. The oxygen atoms arrange themselves into a distorted hexagonal close-packed (hcp) lattice, a densely-packed structure in which atoms essentially occupy the corners of equilateral triangles. Interestingly, Ice XI is an insulator up to and beyond 7 Mbars, the kinds of pressures at which ice exists in Jupiter. Numerous physicists have proposed that ice may become metallic at high pressures, but the simulations suggest that Jovian ice may not necessarily be metallic. The pressures that would be required to make Ice XI can be experimentally achieved in diamond anvil cells, the authors point out. (M. Benoit et al, upcoming paper in Phys. Rev. Lett.)