The magnetic fields of Uranus and Neptune are not as well understood as those of Jupiter, Saturn, or Earth. Earth's magnetic field is generated by the circulation of a liquid iron-nickel alloy, while Jupiter and Saturn's fields are thought to come from hydrogen compressed into a metallic state.
In contrast, the magnetic fields of Uranus and Neptune are believed to arise from the movement of ionically conductive media, where the ions themselves carry the charge. Knowing the specific ions and their proportions could help explain why these ice giants' magnetospheres are misaligned with their rotation and offset from their centers.
Professor Artem R. Oganov of Skoltech explained the difference between ionic and electronic conductivity and where the new ion fits: "The hydrogen surrounding Jupiter's rocky core at those conditions is a liquid metal: It can flow, the way molten iron in the Earth's interior flows, and its electrical conductivity is due to the free electrons shared by all the hydrogen atoms pressed together. In Uranus, we think that hydrogen ions themselves - i.e., protons - are the free charge carriers. Not necessarily as standalone H+ ions, but perhaps in the form of hydronium H3O+, ammonium NH4+, and a series of other ions. Our study adds one more possibility, the H4O2+ ion, which is extremely interesting from the chemical viewpoint."
In chemistry, sp3 hybridization refers to the combination of electron orbitals, creating a template for molecules and ions. For example, a carbon atom with four unpaired electrons forms methane (CH4) when combined with hydrogen. An oxygen atom, with two electron pairs and two valence electrons, forms water (H2O). Adding a hydrogen ion to water creates hydronium (H3O+).
Professor Xiao Dong from China's Nankai University discussed the possibility of adding another proton to hydronium: "But the question was: Can you add yet another proton to the hydronium ion to fill in the missing piece? Such a configuration at normal conditions is energetically very unfavorable, but our calculations show there are two things that can make it happen. First, very high pressure compels matter to reduce its volume, and sharing a previously unused electron pair of oxygen with a hydrogen ion (proton) is a neat way of doing that: like a covalent bond with hydrogen, except both electrons in the pair come from oxygen. Second, you need lots of available protons, and that means an acidic environment, because that's what acids do - they donate protons."
Using computational tools, the team predicted that under extreme conditions - 1.5 million atmospheres of pressure and 3,000 degrees Celsius - aquodiium ions could form.
The researchers believe these ions could be significant in the behavior of water-based media under pressure and containing acid, as found on Uranus and Neptune. This environment could lead to the formation of aquodiium ions, contributing to the planets' magnetic fields and other properties.
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