Jupiter’s core turned out to be partially dissolved in metallic hydrogen

(ORDO NEWS) — Scientists have built a computer model of Jupiter’s interior, which finally converged quite well with the observed data.

Jupiter’s core is small, but the shell of metallic hydrogen turned out to be enriched in heavy elements, the concentration of which gradually increases towards the center of the planet.

In the outer part of the solar system there are planets that are very different from our Earth. The gas giants do not have the usual solid surface, and instead, under the clouds, there is a huge thickness of gases and “ices”, which experiences ultra-high pressures and temperatures.

According to the classical theory, gas giants , which in our system include Jupiter and Saturn, consist of three layers: a massive hydrogen-helium shell, a “mantle” of metallic hydrogen , and a relatively small core of exotic forms of rocks and ice (Uranus and Neptune now emit in a separate class – ice giants).

Until recently, this was impossible to verify. The easiest way to find out the structure of the interior of other planets is to make an accurate measurement of the gravitational field of the planet from a close orbit and, on its basis, build a model of the distribution of matter inside it.

In the 21st century, the gravitational field of the giants was finally explored with the help of high-precision tracking of the trajectory of orbiters – Juno at Jupiter and Cassini at Saturn. A preliminary analysis, released in 2017, showed that early ideas about the bowels of Jupiter diverge significantly from the observed data.

It turned out that its core is “dissolved” in metallic hydrogen: the concentration of “metals”, to which astronomers refer to all elements heavier than helium, gradually decreases with distance from the center and remains significant up to about half the radius of the planet.

In the new work, an international team led by scientists from the Netherlands Institute for Space Research (SRON) has carried out repeated computer simulations of Jupiter’s interior (a preprint of the original paper can be found here ).

This time, they sought to find a self-consistent model that could achieve a more accurate match with both the results of gravitational studies and other observational data.

It turned out that the bowels of Jupiter are heated a little more than previously thought. In this case, their complete mixing does not occur, despite the “liquid” state of the substance. Therefore, the temperature of the cloud layer is lower than expected, and heavy elements are not uniformly distributed inside the planet.

Jupiters core turned out to be partially dissolved in metallic hydrogen 2
The proposed model of the structure of the bowels of Jupiter. Signatures from top to bottom: a shell of molecular hydrogen and helium, a “helium rain” region in which helium is poorly soluble in hydrogen and is released into a separate phase, a layer of metallic hydrogen with an increased concentration of heavy elements, a “dissolved core” with increasing metallicity towards the center, solid a core consisting entirely of heavy elements

The new models completely rule out both a clear transition between the core and the mantle, and its opposite, uniformly mixed heavy elements. Their concentration gradually increases as one moves deeper, which confirms the “dissolved core” hypothesis.

If we assume, according to previous studies, that the total mass of heavy elements in Jupiter is 24-28 Earth (Jupiter itself is 318 times more massive than the Earth), the picture is as follows.

The mass of the inner core of Jupiter, consisting only of heavy elements, does not exceed seven, but most likely four Earth masses.

Two more – mainly water vapor, methane, ammonia and hydrogen sulfide – are in the upper shells of the planet, and the rest, 15-25 Earth masses, is distributed over the lower mantle from metallic hydrogen. There, in addition to “ices”, “rocks” are dissolved – what under normal conditions are silicates and iron alloys.

The new model, unlike the previous ones, also agrees with the observed abundance of heavy elements in Jupiter’s upper atmosphere.

In addition, she confirmed that the zonal wind belts, observed through a telescope as bands on Jupiter’s disk, extend far into the planet. They can be traced to a depth of three thousand kilometers, where the pressure is 100 thousand atmospheres.

The model also makes it possible to clarify the mechanism by which heavy elements hit Jupiter during its formation. Most of all, it is consistent with the bombardment by kilometer-sized planetesimals, and not with a continuous stream of small “rubble”.

Note that, in addition to measuring the gravitational field, there is another method for studying the interior, which is suitable for gas and ice giants in the same way as for rocky planets and stars – this is seismology. It gives much more accurate results than the gravitational one.

Only in the case of bodies that do not have a solid surface, it is necessary to measure not concussions, but continuous oscillations of the gaseous shells of a celestial body. Let’s hope that someday long-lived probes will appear in the atmosphere of Jupiter and other giants that will directly measure their breathing and pulse.


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