Scientists have created a mysterious phase of water – called ‘superionic ice’ – by beaming X-rays through a diamond in the lab.
Extreme conditions are necessary to produce superionic ice, sometimes referred to as ‘hot ice’, which adds to the other well-known phases of water – solid ice, liquid water and vapour gas.
Superionic ice is a special crystalline form, half solid, half liquid – and it’s electrically conductive.
It’s formed at extremely high temperatures and pressures at the centre of planets like Neptune and Uranus in the outer solar system.
Knowing more about the different phases of H2O – of which there are several – could help find life on other planets, the scientists believe.
Scientists used diamonds and a beam of brilliant X-rays to recreate the conditions deep inside planets, and created a phase of water called ‘superionic ice’, at the Advanced Photon Source (APS). They squeezed their ice samples between two pieces of diamond – the hardest substance on Earth – to simulate the intense pressures, and then shot lasers through the diamonds to heat the sample up (apparatus at APS is pictured)
The Advanced Photon Source (APS) was the US government’s high energy X-ray light source facility located in Lemont, Illinois. It was the location where the experiments to create superionic ice went well.
It had been thought superionic ice would not appear until the water was compressed to more than 50 gigapascals of pressure – about the same as the conditions inside rocket fuel as it detonates for liftoff – but these experiments were only at 20 gigapascals.
‘It was a surprise – everyone thought this phase wouldn’t appear until you are at much higher pressures than where we first find it,’ said study co-author Vitali Prakapenka, a University of Chicago professor and beamline scientist at APS.
’But we were able to very accurately map the properties of this new ice, which constitutes a new phase of matter, thanks to several powerful tools.’
Depending on the temperature and pressure in the environment, the solid form of water (H2O), can actually come in more than a dozen structures.
‘Superionic’ – which shouldn’t be confused with ‘supersonic’ – refers to water that has both solid and liquid properties, which happens when water is placed under extreme pressure and heat.
Superionic Ice has oxygen atoms that are tightly packed and locked into place. However, protons can move freely through the lattice similar to electrons and atoms in a metal.
The experiment was conducted at the Advanced Photon Source (APS), the US government’s high-energy Xray light source facility located in Lemont, Illinois.
Its existence was predicted by several models and has already been observed in extreme laboratory conditions.
Researchers in the USA provided the first direct evidence in 2018 for superionic-ice, as it was first suggested in 1988.
However, superionic Ice was previously only glimpsed briefly after researchers sent a shockwave though a droplet water.
This team of scientists now has a reliable method to create, sustain, examine and maintain ice using APS.
APS is a powerful accelerator that accelerates electrons at speeds very close to light speed to produce brilliant beams X-rays.
Prakapenka and colleagues squeezed their ice samples between two pieces of diamond – the hardest substance on Earth – to simulate the intense pressures, and then shot lasers through the diamonds to heat the sample up.
Finally, they sent a beam Xrays through the sample. Based on how the Xrays scatter from the sample, they pieced together the arrangement.
Superionic Ice is a special, crystalline form that is half solid and half-liquid. Here is an artistic rendering
The team was able to map the structure and properties of the ice by looking at it.
Prakapenka stated, “Imagine a cube, a lattice of oxygen atoms at each corner connected by hydrogen.”Prakapenka stated, “Imagine a cube, a lattice of oxygen atoms at each corner connected by hydrogen.
‘When it transforms in to this new superionic Phase, the lattice shrinks, allowing hydrogen atoms and oxygen atoms both to move around, while the oxygen atoms remain in their original positions.
“It’s sort of like a solid oxygen layer sitting in an ocean filled with floating hydrogen atoms.”
This has consequences for how the ice behaves – it becomes less dense, but significantly darker because it interacts differently with light.
Prakapenka says that the full range of chemical and physical properties of superionic-ice has yet to be discovered.
Superionic Ice is formed at extremely high temperatures at the centre planets Neptune and Uranus, in the outer solar systems. This is a cutaway image of Uranus
It is important to map the exact conditions in which different phases occur for, among other reasons, understanding the formation of planets and finding life on other planets.
Scientists think similar conditions exist at the interiors of Neptune and Uranus, and other cold, rocky planets in other solar systems – known as ‘exoplanets’.
These ices have significant influence on the planet’s magnetic fields. This has a huge impact upon its ability to host life.
The Earth’s magnetic fields protect us against harmful incoming radiation and cosmic rayons, while the surfaces of Mars and Mercury are exposed.
Scientists can use the knowledge of magnetic field formation to aid in their search for alien life.
Nature Physics has published the new achievement.