Ice XXI is the latest to join the ranks. It has a tetragonal crystal structure with fairly large repeating units consisting of 152 water molecules, which makes it distinct from all other known phases of ice.<\/p>\n
Related: Weird Ice That Could Form on Alien Planets Observed For First Time<\/a><\/p>\n The repeating unit of ice XXI. (Lee et al., Nat. Mater., 2025)<\/p>\n Don’t expect to whip up a few fancy cubes of ice XXI in your freezer at home, though. Or any kind of freezer for that matter.<\/p>\n The researchers used a diamond anvil cell at the European XFEL facility<\/a> in Germany to squeeze water to pressures of up to 2 gigapascals (about 20,000 times the air pressure at sea level) within 10 milliseconds.<\/p>\n They then released the pressure relatively slowly \u2013 over a leisurely period of one second \u2013 before repeating the process. The whole time, the X-rays captured a million images per second to see how the crystal structure changes.<\/p>\n Ice XXI, it turns out, is one of several possible intermediary stages on water’s way to becoming an exotic phase known as ice VI.<\/p>\n “With the unique X-ray pulses of the European XFEL, we have uncovered multiple crystallization pathways in H2O, which was rapidly compressed and decompressed over 1,000 times using a dynamic diamond anvil cell,” says<\/a> Geun Woo Lee, physicist at the Korea Research Institute of Standards and Science.<\/p>\n Mid Article Promo Launch<\/p>\n The researchers say the discovery of ice XXI suggests that other, still-unknown phases of ice could exist on icy moons and planets<\/a>.<\/p>\n![\"Scientists](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2025\/10\/ececd17a81bb10a160d52971461a85e8.jpeg\"\/)
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