Inspector Juno reveals Jupiter’s cannibalistic past

On the dock, a gas giant accused of having fed on a bunch of infant planets.

In recent years, Mars has become the darling of major aerospace players, starting with SpaceX, which aims to build a colony there. But in the shadow of this scarlet starlet, our solar system is full of other fascinating objects that also deserve the attention of astronomers. This is particularly the case of Jupiter.

This gas giant, by far the largest planet in our solar system. It has a whole host of unique features that are of great interest to researchers. But despite its size, it is very complicated to study, largely because of its distance from Earth (about 750,000 kilometers). This is all the more true for all the phenomena that take place below its superb surface.

What frustrate the specialists, because it is probably where the answers to the most intriguing questions are hidden. So many mysteries remain to be solved. This is particularly the case of mechanisms that allowed it to reach such a size; at present, the history of the formation of Jupiter is still studded with gray areas.

Inspector Juno has a keen eye

This is where Juno comes in. This NASA satellite has been monitoring the gas giant tirelessly since 2016; it measures its composition, the intensity of magnetic and gravitational fields in search of clues to the composition and history of the planet. And recently, she just hit the jackpot. The probe readings showed that the bowels of Jupiter contain a nice surprise.

Thanks to measurements of the gravitational field, the researchers were able to see beyond the surface to collect lots of data on the deep layers of Jupiter – as doctors do in the context of an MRI for example. They thus determined that so-called “heavy” elements were present in abundance in the bowels of the beast.


A feast of planetary embryos

By analyzing the chemical composition of the elements in question, NASA deduced that they were remains of a myriad of embryonic planets – We are talking about planetesimals that Jupiter has devoured unceremoniously. An infantile cannibalism which, according to the researchers, played a major role in the growth of the gas giant.

In a nutshell, these planetesimals are accumulations of rock, dust, and gas that continually pull together under the effect of gravity. This structure is the source of an increasingly intense gravitational force which leads to the absorption of more material, and so on.

If left undisturbed, these planetesimals eventually accumulate enough matter to form a large cohesive celestial body; we are talking about a planet. This is how all the planets of the solar system were born, including our Earth. But if they don’t have room to grow, then they compete; the heavier of the two will eventually assimilate the smaller. And that’s exactly what happened to these planetesimals.

They were born a little too close to a Jupiter in full growth spurt who didn’t have to be asked to swallow them raw. The gas giant would thus have devoured the equivalent of a few dozen planet Earthswhich could represent hundreds of infant planets.

An artist’s impression of a protoplanetary disk, a mass of material from which the embryos of planets can emerge. © Keck Observatory

To know Jupiter is to know the solar system

For the little anecdote, we can see a tenuous link with the god Saturn who, according to Roman folklore, would have devoured all his children following a prophecy which stipulated that one of them would end up replacing him.

But it is not this very abstract filiation that makes these works so interesting. This new information on the structure and the entrails of Jupiter will make it possible to specify the existing models, in particular those which are interested in the first hours of the universe.

Indeed, it is not only planetesimals that have borne the brunt of Jupiter’s passage. Because of the dantesque gravitational force it generates, it played a very important role in setting up the structure of our solar system (see Migration de Jupiter). Knowing the details of its growth therefore makes it possible to learn more about the history of our cosmic neighborhood as a whole… and all this thanks to a small probe which has been doing titanic work alone for six years already.

The text of the study is available ici.

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