Jupiter would have devoured the planetesimals during his youth


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[EN VIDÉO] Fly over Jupiter with the Juno spacecraft
Discover Jupiter as you’ve never seen it before thanks to the work of a citizen scientist. Using images collected by the Juno spacecraft, he was able to create a 3D model of the Jovian surface, of which he offers a breathtaking overview.

Fifth planet in our Solar System in order of distance from ours star, Jupiter instead it is the largest (almost 140,000 kilometers in diameter) and the most massive (more than 300 times the mass of the Earth). Similar in composition to Sunessentially consisting ofhydrogen and’heliumthe gas giant probably formed by accretion of materials in the nebula solar. But the presence of the so-called metallic elements, heavier than helium, seems to indicate that Jupiter not only accumulated gaseous materials during its first phases of existence, but also metallic elements, potentially coming from solid protoplanets, called planetesimals.

Many probes to study the giant of the Solar System

Despite visiting several probes since the early 1970s, Jupiter is still full of mysteries: the beautiful scrolls of gas known to him are only representative of the upper 50 kilometers ofatmosphere of the planet, thus hindering any vision one may have of its internal structure and composition.

In 1995, the probe Galileo stands up orbit around Jupiter and dropped a small atmospheric probe into it, providing us with valuable information on the composition of the upper layers of its atmosphere, before being crushed by the fort pressure who reigns there. It was therefore necessary to wait until 2016 for the probe Juno of the NASA it is placed in orbit around Jupiter with the aim of collecting data on the inner layers of the planet, in particular through the study of its gravitational field. It is still in operation today, and NASA plans to terminate the mission in 2025.

Formative processes still debated

Although the idea that Jupiter was formed by the accretion of gas in the cloud protosolar is commonly accepted, the period and the processes of accretion of the metallic elements are still a matter of debate. Most of the scientific community agrees that during its formation, the planet first accumulated rock material, then followed a rapid period of gaseous accretion, giving it its current size. But the accretion period of the rock material remains very vague: could the planet have accumulated large rock bodies – planetesimals – during its early stages of existence, or would it have limited itself to capturing debris?

A new study claims to be able to decide, thanks to the exploitation of gravitational data collected by Juno: according to the authors, the clues to the formation and evolution of Jupiter reside in the depths of its atmosphere. By mapping the presence of metallic elements in the planet’s core, obtained from measurements made by the Gravity Science instrument mounted on the spacecraft, the scientists were able to highlight the highly inhomogeneous nature of its atmosphere: most of the metallic elements are concentrated towards the center , for a total mass varying between 11 and 30 times the earth’s mass.

Therefore, Jupiter would have continued to accumulate large quantities of metallic elements during the extension of its gaseous envelope.

According to the authors of the study, when a protoplanet is sufficiently massive, it would begin to eject the surrounding debris, due to their too small mass; however, the richness of metallic elements observed in the gas giant it could not have been reached before Jupiter was too massive to repel all debris, thus implying the role of more massive rock bodies in the planet’s early growth stages.

Therefore, Jupiter would have continued to accumulate large quantities of metallic elements during the extension of its gaseous envelope, questioning the hypothesis of two distinct periods of accretion. Furthermore, the inhomogeneous nature of Jupiter’s atmosphere appears to demonstrate the absence of effective convection processes in its inner layers, which scientists previously thought were present.

In addition to a much more precise vision of the internal composition of Jupiter and its evolutionary processes, this study could also have repercussions on the study of exoplanets gas and them metallicity.

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