Uranus and Neptune are cold, icy mysteries. That’s them sa radically different from the rest of the planets in the solar system, that scientists feel that a better understanding of these two giants is crucial to understanding how planets form. Now, a new modeling tool offers an opportunity for what scientists have wanted for decades: a glimpse inside.
They begin by looking at the thermal and electrical patterns on these planets that are impossible to reproduce in a lab.
On their respective surfaces, Uranus and Neptune would be the two most forgettable planets in the solar system. They lack neither the flair of Jupiter and Saturn nor the striking colors of Mars and Mercury. They are different shades of blue – both.
But look a little harder, and you will see two outliers. The designation as “ice giants” means that each of the planets is made of hot, dense liquids. These liquids consist of “icy” matter – in this case water, methane and ammonia, all surrounded by a rocky core.
This has led some scientists to suggest that the two ‘bare’ nuclei are gas giants such as Saturn and Jupiter, discovered for reasons that are not clear.
Federico Grasselli and Stefano Baroni, first and last author of the paper published in July in Nature communication detail the model, offers another compelling reason: “Neptune and Uranus are also probably composed mainly of water.” Although neither is suspected of sustaining life, only the existence of water in such strange conditions could reveal important facts about how planets form, especially exoplanets.
“In recent years, they have also received more attention as a test bench to study classes of exoplanets on water, which may be common in extra-solar planetary systems: the study of abundant planets and men in water is currently large. interest in the quest for extraterrestrial life, ”Grasselli says Inverse via e-mail.
And learning about the interior of a planet, the couple say, can be a crucial first step in learning everything.
“Our knowledge of planetary interiors is based on the functions of the planet’s surface and magnetic field, which are themselves influenced by the physical characteristics of their internal structure, such as the transport of energy, mass, and charge via the internal interlayers, ”Grasselli explains.
Dive into – Measurements accurate enough to mimic the interior level of a planet were a complex endeavor, with a quantum mechanical basic theory of heat and charge transport as the basis for the study.
Calculations, Grasselli says, were “performed on super-performing supercomputers” for months. The study required them to create new data analysis tools that were able to obtain reliable values for thermal and electrical conductivity.
“All in all a difficult challenge on several fronts,” says Grassellie, “but we have made it.”
The team studied water in three forms, liquid, gas, and superionic. One would expect “solid” to be the third on this list, but Grasselli and Baroni explain that ice on these planets is not the same as the ice we are thinking of. On Uranus and Neptune, the water is different – denser, and with an electric charge.
“All in all, a tough challenge on several fronts … but we made it.”
Superionic water is best viewed between liquid and solid phases.
“The oxygen atoms of the H2O molecule are organized in a crystalline lattice, while hydrogen atoms diffuse freely as in a charged liquid,” the couple explain.
All three forms of water on Uranus and Neptune form thermal and electric currents. These can be quite powerful: Neptune has the strongest winds in the solar system, going faster than 2,000 km / h (1,200 mph).
Thermal and electrical output also provide important data on planetary history. “The thermal and electric transport coefficients dictate the history of the planet, how and when it was formed, how it cooled,” the authors say.
Here, the researchers found that the superionic water has a much greater conductivity than previously proposed, especially in terms of creating magnetic fields. Superionic water exists mainly in the dense layers below the convective fluid region, where planets generate their magnetic fields.
Especially in the case of Uranus, which NASA called the ‘Sideways Planet’ because of its strange magnetic fields and how it turns to the side, this can be a crucial piece of the puzzle to figure out how it existed.
And it’s not just for these two. Grasselli tells Inverse that his team’s method could be used to “study the transport properties of salt water in the global oceans beneath the icy crust, say, of the moons of Jupiter and Saturn.” A few places in the solar system are as closely observed as the moons of these two giants, especially those with the potential for aquatic life such as Europe.
Abstract: The influence of the inner structure and thermal history of planets on their observational functions, such as lightness and magnetic field, depends critically on the poorly known heating and charge transfer properties of their internal layers. The thermal and electrical conductivities of different phases of water (liquid, solid and super-ionic) that occur in the interior of ice-giant planets, such as Uranus or Neptune, are evaluated from equilibrium ab initio molecular dynamics, leading to recent advances in the theory is practiced and data analysis of transport in extended systems. The implications of our findings on the evolutionary models of the ice giants are briefly discussed.
