The ice giants of our solar system are bizarre worlds of extremes. For example, if you were born on one of the poles of Uranus, at sunset you would be middle-aged and very old, 84 years old, before it was time for a second sunrise At the time of a second dawn on Neptune, a dark, cold world, lashed by supersonic winds that can reach 1
“Next to helium, hydrogen and oxygen are the most common elements in the universe. It is easy to deduce that water is one of the main components of many celestial bodies. Ganymede and Europa, satellites of Jupiter, and Enceladus, satellites of Saturn, present icy surfaces beneath which lie oceans of water. Neptune and Uranus probably also consist mainly of water, “say Federico Grasselli and Stefano Baroni – scientists from SISSA in Trieste and UCLA who, thanks to computer simulations on their water, paved the way for modeling the interior of the ice giants Uranus and Neptune on a microscopic scale, to unlock stories that go back billions of years.
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New theoretical method
A new theoretical method allows them to analyze thermal and electrical processes taking place under physical conditions that are often not experimentally reproducible, and with a much simpler and cheaper approach. In this study, the scientists analyzed the conduction of electricity and heat from water under extreme temperature and pressure conditions, such as those found in giant ice planets as well as in many exoplanets outside of them. Indeed, studying the phenomena that occur beneath their surface is key to understanding the evolution of these celestial bodies, determining their ages, and shedding light on the geometry and evolution of their magnetic fields.
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“Our knowledge of planetary interiors” – they add – “is based on the features of the planet’s surface and magnetic field, which are themselves influenced by the physical properties of their internal structure, such as the transport of energy, mass and charge through the interior interlayers. For this reason, we have developed a theoretical and computational method to calculate the thermal and electrical conductivity of water in the phases and conditions occurring in such celestial bodies, starting with state-of-the-art simulations of the microscopic dynamics of a few hundred atoms up to including the quantum nature of electrons without further ad hoc approximation. By simulating the atomic scale for fractions of a nanosecond, we can understand what has happened to enormous masses on time scales spanning billions of years. “
Superionic – “Not the ice or water we are used to on earth”
The scientists analyzed three different water phases: ice, liquid and superion under the extreme temperature and pressure conditions typical of the inner layers of these planets. Black, hot, superionic ice is a bizarre form of water that could make up most of the vast icy planets in the entire universe.
The discovery of superionic ice, reports Joshua Skokol for Quanta, who was not involved in the study that was theoretically predicted more than 30 years ago, “may solve the puzzle of what giant icy planets like Uranus and Neptune are made of. They are now believed to have gaseous, chemically mixed outer shells, a liquid layer of ionized water underneath, a solid layer of superionic ice that makes up most of their interior, and rocky centers. “
“It really is a new state of matter”
Superionic ice is not a completely new phase in water, says physicist Livia Bove from the National Center for Scientific Research in France and the Pierre and Marie Curie Universities.
Grasselli and Baroni explain: “In such exotic physical conditions we cannot think of ice cream as we are used to. Even water is different, more dense, with several molecules dissociated into positive and negative ions and thus carrying an electrical charge.
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Superionic water lies somewhere between the liquid and the solid phase: the oxygen atoms of the H2O molecule are organized in a crystal lattice, while hydrogen atoms diffuse freely like in a charged liquid. “Studying the thermal and electrical currents produced by water in these three different forms is important to shed light on many unsolved problems.
Existence of a frozen core
The two scientists also state that “internal electrical currents are the basis of the planet’s magnetic field. If we understand how the former flow, we can learn a lot more about the latter. “And not only that.” The thermal and electrical transport coefficients determine the history of the planet, how and when it was formed, and how it cooled. It is therefore important to analyze them with the appropriate tools as we developed them. In particular, the heat conduction properties resulting from our study suggest that the existence of a frozen core may explain the unusually low luminosity of Uranus due to an extremely low heat flux from its interior to the surface. “
In addition, the electrical conductivity found for the superionic phase is much greater than assumed in earlier models of magnetic field generation in Uranus and Neptune. Since superionic water is believed to dominate the dense and inert planetary layers below the convective fluid region where their magnetic field is generated, this new evidence could have a major impact on studying the geometry and evolution of the magnetic fields of the two planets.
The Daily Galaxy, Sam Cabot, via SISSA and Quanta
Photo credit: NASA Ice Worlds