[ad_1]
It took one of the most powerful lasers on the planet, but the scientists did it. They confirmed the existence of superionic ice – an icy water that can remain solid at thousands of degrees of heat.
This bizarre form of ice is possible thanks to tremendous pressure and the results of the experiment could illuminate the interior structure of giant glacial planets such as Uranus and Neptune.
On the Earth's surface, the boiling and freezing temperatures of water vary very little – usually when it is very hot, and when it is very cold and very cold. But these two changes of state are made according to the pressure (that is why the boiling point of the water is lower at high altitude).
In the void of space, water can not exist in its liquid form. It boils immediately and vaporizes even at -270 degrees Celsius – the average temperature of the Universe – before it clears into ice crystals.
But it has been theorized that in extremely high pressure environments, the opposite happens: the water solidifies even at extremely high temperatures. National laboratory scientists Lawrence Livermore have directly observed this for the first time recently, as explained in detail an article last year.
They created Ice VII, which is the crystalline form of ice above 30,000 times the atmospheric pressure of the Earth, or 3 gigapascals, and projected with the help of lasers. The resulting ice had a conductive flow of ions, rather than electrons, which is why it is called superionic ice.
Now they have confirmed with follow up experiences. They proposed that the new form be named Ice XVIII.
In the previous experiment, the team could only observe general properties, such as energy and temperature; the finer details of the internal structure remained elusive. So they designed an experiment using laser pulses and X-ray diffraction to reveal the crystal structure of the ice.
"We wanted to determine the atomic structure of superionic water," said LLNL physicist Federica Coppari.
"But given the extreme conditions under which this elusive state of matter is predicted to be stable, compressing water at such pressures and temperatures and simultaneously taking snapshots of the atomic structure was an extremely difficult task requiring a concept. innovative experiment. "
Here is this design. First, a thin layer of water is placed between two diamond anvils. Then, six giant lasers are used to generate a series of progressively increasing shock waves in order to compress water at pressures of up to 100 to 400 gigapascals, ie 1 to 4 million times. the atmospheric pressure of the Earth.
At the same time, they produce temperatures between 1,650 and 2,760 degrees Celsius (the Sun's surface is 5,505 degrees Celsius).
This experiment was designed to freeze water when it was compressed, but pressure and temperature conditions could only be maintained for a fraction of a second, and physicists were uncertain of the formation and temperature. ice crystal growth.
So they used lasers to blow a tiny piece of iron foil with an additional 16 pulses, creating a plasma wave generating an X-ray flash exactly at the right moment. These chips diffracted on the crystals inside, showing that the compressed water was really frozen and stable.
"The X-ray diffraction patterns we measured are an unequivocal signature in the formation of dense ice crystals during ultra-fast shockwave compression, demonstrating that the nucleation of solid ice into the atmosphere is the most important step in the process. Liquid water is fast enough to be observed at the nanosecond of experience, "said Coppari.
These X-rays showed a structure never before seen: cubic crystals with oxygen atoms at each corner and an oxygen atom at the center of each face.
"The discovery of direct evidence of the existence of a crystal lattice of oxygen brings the last missing piece to the puzzle regarding the existence of ice in superionic water," said physicist Marius Millot of LLNL.
"This gives additional strength to the evidence of the existence of superionic ice that we collected last year."
The result reveals a clue as to how ice giants such as Neptune and Uranus could have such strange magnetic fields, inclined at odd angles and with equators that do not circle the planet.
Previously, it was thought that these planets had a fluid ocean of ionic water and ammonia instead of a mantle.
But the team's research has shown that these planets could have a solid mantle, like the Earth, but made of hot superionic ice instead of hot rock. Superionic ice being very conductive, it could influence the magnetic fields of the planets.
"Since water ice in the inner conditions of Uranus and Neptune has a crystal lattice, we argue that superionic ice should not flow like a liquid such as the outer iron core of the It is probably better to imagine that superionic ice would flow in the same way.The earth's mantle, made up of solid rocks, flows and supports large-scale convection movements over very long geologic time scales. " Millot.
"This can dramatically affect our understanding of the internal structure and evolution of icy giant planets, as well as their many extrasolar cousins."
The search was published in Nature.
[ad_2]
Source link