Superionic ice: Scientists discover a new phase of water

In high school, we learned that there are only three states of matter. But in reality, there are more than that and it seems the list keeps growing as science advances with each passing year. Currently, we know that water exists in around 20 phases. Each of these phases refers to how the hydrogen and oxygen atoms stack up in different temperature and pressure conditions.

A recent experiment has revealed a newer phase of water that exists as supersonic ice with a strange black coloured appearance. The new phase exists under the same temperature and pressure conditions as present in the centre of the Earth and it is the 18th phase of ice that has been discovered. The team behind the experiment believe that the discovery of the new phase could help unravel the mysteries hiding in other planets with icy cores.

Professor Pierfranco Demontis had theorized the existence of such a supersonic ice way back in 1988. Then in 2018 researchers from Lawrence Livermore National Laboratory in California were able to experimentally provide evidence of it. Unfortunately, the team could only maintain the phase for 20 nanoseconds before it dissolved away.

In a new experiment, a team of researchers from Advanced Photon Source at Argonne National Laboratory were able to recreate a much stabler version for this mysterious phase allowing them to study more about its properties. The result of their studies is published in the Nature Physics journal.

In order to create a stable variant they the researchers applied enormous pressure to a water droplet using 0.2-carat diamonds and then blasted it with a laser. The hardness of diamond helped create pressures equivalent to 3.5 million times that of the Earth’s atmosphere while heating it to temperatures similar to that of the Sun’s surface.

This allowed the team to observe the phase in a microsecond range – much longer than the previous experiment. Using an electron accelerating device called a synchrotron, they applied X-ray diffraction to identify the lattice structure of the new phase.

The black supersonic ice is a weird phase, to say the least. At the atomic level, its oxygen atoms exist as they would in the normal ice solids. But the hydrogen atom in them appears to be in an ionized state, allowing them to float freely through the ice. It looks as if the oxygen atoms are floating in a sea of hydrogen.

The peculiar black color of the substance is also caused by this fluid-like nature of hydrogen. The free-flowing ions block the light that enters the ice in a predictable way creating the black color.

 It is known that free-floating hydrogen ions can create magnetic fields. Scientists are wondering if the planets like Uranus or Neptune has supersonic ice trapped inside them, thus playing a crucial role in creating the magnetosphere that exists in these planets.

Magnetospheres shield planets from harmful solar radiation and cosmic rays thus giving the chance for life to proposer there under the right conditions. Researchers believe that identifying the presence of supersonic ice could serve as a guide as we are searching for extraterrestrial life forms.

We still have a lot of studies in front of us to uncover other properties of the phase including its conductivity, viscosity and chemical stability. Using those we might be able to even predict where else we might find this mysterious phase of ice.

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