This Discovery Could Shake Up Fundamental Chemistry
Two new forms of frozen salt water have recently been discovered that could potentially help researchers solve a mystery regarding the ice-covered moons in our Solar System.
The atoms of hydrated sodium chloride, also known as salt water ice, rearrange themselves into previously unidentified structures that have a greater proportion of water molecules than salt when exposed to lower temperatures and higher pressures than those found in nature on Earth.
The unique chemical signature of the substance found on the surface of Jupiter’s moon Europa, which appears to be more watery than expected, may be explained by this phenomenon.
According to Baptiste Journaux, a scientist specializing in Earth and space, fundamental scientific discoveries are now rare, and the discovery of these compounds under such exotic conditions is an exciting time.
Salt and water, also known as sodium chloride and dihydrogen oxide, are abundant on Earth, and when combined, they create a solution where salt molecules dissolve throughout the water molecules. The salt in the solution lowers the freezing point compared to unsalted water, but at temperatures typical of Earth atmospheric conditions, it will eventually freeze.
However, when the solution freezes, the molecules create a rigid lattice structure known as a hydrate, which on Earth only has one configuration: one salt molecule for every two water molecules.
Unlike Earth, moons like Europa, Ganymede, and Enceladus orbiting Jupiter and Saturn, respectively, have different conditions that contain salt and water. Their surfaces exposed to space’s near vacuum, which can get extremely cold, have a thick coat of ice that covers oceans that could be over 100 times deeper than Earth’s waters, leading to extreme pressures and temperatures.
Journaux and his colleagues investigated the impact of salt on ice production by compressing a small amount of salt water in a diamond anvil cell under extremely cold conditions, reaching pressures up to 25,000 times Earth’s atmospheric pressure and lowering temperatures to -123 degrees Celsius (-190 degrees Fahrenheit).
Surprisingly, the researchers discovered two new arrangements of salt and water molecules under the experiment’s conditions. One hydrate consisted of two salt molecules for every 17 water molecules, while the other had 13 water molecules for one salt molecule. Both structures differ greatly from the one salt and two water molecule structure observed naturally on Earth but align with the watery chemical signatures detected on the ice moons.
According to Journaux, the structure of the newly identified hydrate is what planetary scientists have been anticipating for some time.
The main factor contributing to the emergence of these new hydrates is pressure, which causes the molecules to compress and find new ways to coexist. One of the newly identified hydrates, the one with 17 water molecules, remained stable at temperatures as low as -50 degrees Celsius, even after the pressure was released, suggesting it could be present on Earth, possibly under the Antarctic ice.
Further research will be necessary to determine whether the discovery of the new hydrates can solve the mystery of the icy moons. The researchers suggest that determining the infrared spectra of the hydrate will be necessary in future studies, but its hyperhydrated structure could potentially explain the long-standing mystery surrounding the unidentified hydrate phase at the surfaces of Europa and Ganymede.
The research has been published in Proceedings of the National Academy of Sciences.
