A bizarre form of water may help explain Uranus’s messy magnetism: ScienceAlert

One of the most special things about Uranus and Neptune is their magnetic fields. Each of these planets has a hot mess of a magnetosphere, deviated and wildly tilted from its axis of rotation in a way not seen on any other planet.

It’s not entirely clear why, but thanks to a team of researchers from China and Russia, we may have a new piece of the puzzle: a very strange, ionized form of water called aquodiium, which could be found deep in the extremely high-pressure interior of these regions. prevent. strange, icy worlds.

Aquodiium consists of a normal water molecule with two extra protons, giving it a net positive charge that – in sufficient quantities – could produce a planetary magnetic field like that of Uranus and Neptune.

Planetary magnetic fields extend far into space around the planets that produce these fields. However, they are generated deep within the planet by moving charges, although the precise mechanism can vary.

On Earth, it’s the iron-nickel alloy that sloshes around the core, rotating, convecting and electrically conducting, converting all that kinetic energy into electron currents. in what is called a dynamo. For Jupiter and Saturn, scientists think it is metallic hydrogen that provides a channel for flowing electrons.

Earth, Jupiter and Saturn have relatively pure magnetic fields that resemble that of a huge bar magnet running along the planet’s rotation axis, with the field lines neatly connecting a north and south pole like a cage.

In contrast, the magnetic poles of Uranus and Neptune are tilted 59 and 47 degrees, respectively, from their axis of rotation, and the magnetic field lines are constantly changing and shifting. And they’re not really centered in the cores of the planets.

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A possible explanation is that the magnetic fields can be generated by an ionically conductive liquid, where the ions are the charge carriers and not the liquid that acts as a channel for electrons.

‘The hydrogen surrounding Jupiter’s rocky core [high-pressure] conditions is a liquid metal: it can flow, as molten iron flows in the interior of the Earth, and its electrical conductivity is due to the free electrons shared by all the hydrogen atoms pressed together,” explains theoretical chemist, mineralogist and physicist Artem Oganov. from the Skolkovo Institute of Science and Technology in Russia.

“In Uranus we think that hydrogen ions themselves – that is, protons – are the free charge carriers.”

So the question is which ions? Some, like ammonium, are obvious. But could the planets’ water molecules also play a more important role in the process?

Led by physicist Jingyu Hou of Nankai University in China, a team of researchers went back to basic principles combined with models of how molecules can evolve, delving into a concept called chemical hybridization.

This is when an atom’s orbital elements are mixed or combined to create an atom that can bond in new ways. There are several types of hybridization, but the relevant one here is sp3 hybridization, in which four orbitals form a tetrahedral arrangement around the central nucleus.

Each of the four points of the tetrahedron has either a lone electron that can bond with another atom, or an electron pair that cannot form bonds with other atoms.

Oxygen has two individual electrons and two electron pairs in the outer shell. If you attach a hydrogen atom to each of the available valence electrons, you get H2O-water.

Sometimes hydrogen without its electron – also known as a plain old proton – will bond with one of its electron pairs to form a molecule called a hydronium ion.

A diagram explaining the formation of aquodiium. (Skoltech)

‘The question was: can you add another proton to the hydronium ion to fill in the missing piece? Such a configuration is energetically very unfavorable under normal circumstances, but our calculations show that there are two things that can make this happen,” says physicist Xiao Dong of Nankai University.

‘First, very high pressure forces matter to shrink its volume, and sharing a previously unused electron pair of oxygen with a hydrogen ion (proton) is a nice way to do that: like a covalent bond with hydrogen, except that both electrons in the pair Second, you need a lot of available protons, and that means an acidic environment, because that’s what acids do: they donate protons.”

The researchers performed computational modeling, and under conditions similar to those believed to exist within Uranus and Neptune, this is what happened. At temperatures around 3,000 degrees Celsius (5,430 Fahrenheit) and a pressure of 1.5 million atmospheres, protons bond with hydronium to form H4O2 – aquodium.

Of course, it’s still theoretical. More detailed observations of the two outer planets will be needed to further investigate the possibility; but the findings give us a new way to understand the blue oddballs Uranus and Neptune.

And they also have implications for chemistry in general, representing, the researchers write, “an important addition to traditional physical and chemical theories such as the valence shell-electron pair repulsion model, proton transfer, and acid-base theory.”

The research was published in Physical assessment C.

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