Two newly discovered forms of frozen salt water could help scientists unravel the mystery of the solar system’s ice-covered moons.
Subjected to higher pressures and lower temperatures than are found naturally on Earth, the atoms in hydrated sodium chloride, better known as salt water ice, have organized themselves into previously unknown structures that contain a much higher percentage of water molecules than salts. .
This may explain the strange chemical characteristics of the material on the surface of Jupiter’s moon Europa, which turned out to be more watery than scientists expect.
“Fundamental discoveries are rarely made in science these days,” says Earth scientist and astronaut Baptiste Journeau of the University of Washington. “Salt and water are well known in terrestrial conditions. But then we are completely ignorant. And now we have these planetary bodies, which probably contain familiar compounds “For us, but under very strange circumstances.”
When salt and water are combined, sodium chloride and hydrogen peroxide, the salt molecules dissolve into the water molecules, forming a solution. The presence of salt lowers the freezing point of the solution compared to unsalted water, but as the temperature continues to drop under typical Earth weather conditions, it will eventually freeze.
When they do this, the molecules form a rigid lattice structure known as a hydrate. On Earth (outside the lab), this structure has only one composition: one molecule of salt for every two molecules of water.
On moons such as Europa and Ganymede, which orbits Jupiter, and on Saturn’s moon Enceladus, scientists have also found evidence of salt and water, but the conditions in which they are found are somewhat different from Earth’s.
And the surfaces of these distant worlds are subject to intense cold in the near void of space, far from the sun. Beneath the ice sheets are oceans that in some cases can be 100 times thicker than the deepest waters on Earth, causing extreme pressures and temperatures.
The researchers decided to study the effect of salt on ice production. They compressed a small block of salt water in a diamond anvil cell in cold conditions, creating a pressure 25,000 times Earth’s atmospheric pressure, while lowering the temperature to -123 degrees Celsius (-190 degrees Fahrenheit).
“We were trying to measure how the salt affected the amount of snow we could get because the salt acts like an antifreeze,” Journo explains. grow”.
Under the conditions of their experiment, the researchers saw the emergence of two new layouts of the salt and water molecules. One showed two molecules of salt for every 17 molecules of water. The other contains 13 water molecules per salt molecule. Both are very different from a single salt, and this is water that is naturally observed on Earth and is consistent with the chemical signatures of water observed on icy moons.
The researchers say the key factor is pressure, which compresses molecules and forces them to find new ways to coexist. But even when the pressure was released, one of the newly identified hydrates, containing 17 water molecules, remained stable down to -50 degrees Celsius. This indicates that they can be found here on Earth, perhaps under the ice of Antarctica.
Further research is needed to determine if this discovery can solve the mystery of the icy moon.
Study published in Proceedings of National Academy of Sciences.
Source: Science Alert
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