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19 July 2017

Formation of ‘Alien’ Ice VII Observed for First Time Ever

Given just how abundant water is here on Earth, the idea than any form of ice could be considered rare may seem like an inaccurate assertion. However temperatures and pressures only exist on the Earth’s surface within a fairly limited range, and once you get out of our protective atmosphere and into the depths of space, physics can operate in some truly wondrous ways.

The vast majority of the ice formed under the atmospheric pressure of Earth forms with the familiar hexagonal crystal structure with which we are most accustomed, but under different conditions ice can in fact exist as one of at least 15 varying forms, each with its own unique molecular arrangement.

One such form is Ice VII, sometimes referred to as ‘hot ice’ due to its ability to withstand temperatures much higher than those which would reduce conventional ice to a puddle. This cubic crystal phase of ice forms under extremely high pressures and temperatures, such as during a collision between comets and small planets. Ice VII is thought to be present on the ocean floor of Saturn’s moon Titan, as well as upon other watery exoplanets, but attempts to recreate and observe its formation back on Earth have so far been fruitless; until now that is.

A team working out of Stamford University recently published a paper in the journal Physical Review Letters detailing their breakthrough in creating Ice VII under laboratory conditions on Earth, allowing for the formation of this rare structure to be observed properly for the very first time.

Team member Wendy Mao said of the study and its results, “There have been a tremendous number of studies on ice because everyone wants to understand its behaviour. What our new study demonstrates, and which hasn’t been done before, is the ability to see the ice structure form in real time.”

In order to create Ice VII in the lab the team fired an intense laser upon a sample of water, which was itself held in situ between two platelets; one made of diamond and coated with gold, and one comprised of quartz. The laser actually vaporises the diamond, which in turn generates a pressure shock 50,000 times greater than the Earth’s atmospheric pressure at sea level. It is this huge influx of pressure which results in the formation of the illusive Ice VII.

The formation, which occurs over a time span of just 6 nanoseconds, was recorded using femtosecond-long X-ray pulses generated by the X-ray Free Electron Laser at SLAC's Linac Coherent Light Source. The interaction between the X-rays and the transforming water allows the researchers to characterise the changing molecular structure.

“These experiments with water are the first of their kind, allowing us to witness a fundamental disorder-to-order transition in one of the most abundant molecules in the universe,” says team member Arianna Gleason. “Learning about the icy interiors [of icy satellites and planets] will help us understand how the worlds in our solar system formed and how at least one of them, so far as we know, came to have all the necessary characteristics for life.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.