Ice V, pronounced "ice five", is a monoclinic crystalline phase of water, formed by cooling water to 253 K at 500 MPa. It has a density of 1.24 g cm3 (at 350 MPa).
Ice V has a complicated structure, including 4-membered, 5-membered, 6-membered, and 8-membered rings and a total of 28 molecules in the unit cell.Ganymede's interior probably includes a liquid water ocean with tens to hundreds of kilometers of Ice V at its base.
^Drost-Hansen, W. (1969-11-14). "The Structure and Properties of Water. D. Eisenberg and W. Kauzmann. Oxford University Press, New York, 1969. xiv + 300 pp., illus. Cloth, $10; paper, $4.50". Science. 166 (3907): 861. doi:10.1126/science.166.3907.861. ISSN0036-8075.