Jupiter’s bowels are filled with the remains of baby planets that the gas giant swallowed as it expanded to become the giant we see today, scientists have found. The findings come from the first clear look at the chemistry beneath the planet’s cloudy outer atmosphere.
Despite being the largest planet in the solar system, Jupiter disclosed very little about its inner workings. The telescopes captured thousands of images of the swirling vortex clouds in the gas giant’s upper atmosphere, but these Van Gogh storms also act as a barrier blocking our view of what’s below.
“Jupiter was one of the first planets to form in our solar system,” in the first million years after the solar system formed, about 4.5 billion years ago, lead researcher Yamila Miguel, an astrophysicist at Leiden University in the Netherlands, told Live Science. almost nothing for sure about how he formed, she added.
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In the new study, researchers were finally able to peer beyond Jupiter’s murky cloud cover using gravitational data collected by NASA’s Juno space probe. This data allowed the team to map the rocky material at the giant planet’s core, which revealed a surprisingly high abundance of heavy elements. The chemical composition suggests that Jupiter devoured baby planets, or planetesimals, to fuel its expansive growth.
Growing up a gas giant
Jupiter may be predominantly a swirling ball of gas today, but it began its life by accumulating rocky material — just like every other planet in the solar system. like the planet gravity pulling in more and more rocks, the rocky core became so dense that it began pulling in large amounts of gas from long distances – predominantly hydrogen and helium left over from the Sun‘s – to form its huge gas-filled atmosphere.
There are two competing theories about how Jupiter managed to collect its early rock material. One theory is that Jupiter accumulated billions of smaller space rocks, which astronomers call pebbles (although these rocks are likely closer in size to boulders than actual pebbles).
The opposing theory, which is supported by the findings of the new study, is that Jupiter’s core was formed from the absorption of many planetesimals – large space rocks that span several kilometers, which, if undisturbed, could have acted as seeds. of which minor rocky planets I liked Earth or Mars could develop.
However, until now it has not been possible to say definitively which of these theories is correct. “As we cannot directly observe how Jupiter was formed, we have to piece together the information we have today,” said Miguel. “And that’s not an easy task.”
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probing the planet
To try to settle the debate, the researchers needed to build an image of Jupiter’s interior. “Here on Earth, we use seismographs to study the interior of the planet using earthquakes,” said Miguel. But Jupiter has no surface to place these devices on, and Jupiter’s core is unlikely to have much tectonic activity anyway, she added.
Instead, the researchers built computer models of Jupiter’s innards by combining data, which was predominantly collected by Juno, as well as some data from its predecessor Galileo. The probes measured the planet’s gravitational field at different points around its orbit. The data showed that rocky material aggregated by Jupiter has a high concentration of heavy elements, which form dense solids and therefore have a stronger gravitational effect than the gaseous atmosphere. This data allowed the team to map small variations in the planet’s gravity, which helped them see where rocky material is located within the planet.
“Juno provided very accurate gravity data that helped us constrain the distribution of material within Jupiter,” said Miguel. “It’s very unique data that we can only get from a spacecraft orbiting the planet.”
The researcher’s models revealed that there is an equivalent of between 11 and 30 Earth masses of heavy elements inside Jupiter (3% to 9% of Jupiter’s mass), which is much more than expected.
Pebbles vs Planetesimals
The new models point to a planetesimal origin of Jupiter because the pebble accretion theory cannot explain such a high concentration of heavy elements, Miguel said. If Jupiter had initially formed from pebbles, the eventual start of the gas accretion process, once the planet was large enough, would have immediately ended the rocky accretion stage. This is because the growing layer of gas would have created a pressure barrier that prevented additional pebbles from being pulled into the planet, explained Miguel. This phase of reduced rock accretion would likely have given Jupiter a much reduced abundance of heavy metals, or metallicity, than the researchers calculated.
However, planetesimals could have clustered in Jupiter’s core even after the gas accretion phase began; this is because the gravitational pull on the rocks would have been greater than the pressure exerted by the gas. This simultaneous accretion of rocky material and gas proposed by the planetesimal theory is the only explanation for the high levels of heavy elements inside Jupiter, the researchers said.
The study also revealed another interesting finding: Jupiter’s interior doesn’t mix well with its upper atmosphere, which goes against what scientists had previously expected. The new model of Jupiter’s interior shows that the heavy elements that the planet absorbed remained largely close to its core and lower atmosphere. The researchers had assumed that convection mixed Jupiter’s atmosphere, so that hotter gas near the planet’s core would rise into the outer atmosphere before cooling down and falling back down again; if this were the case, the heavy elements would be mixed more evenly throughout the atmosphere.
However, it is possible that certain regions of Jupiter may have a small convection effect, and more research is needed to determine exactly what is happening within the gas giant’s atmosphere, Miguel said.
The researchers’ findings could also change the origin stories of other planets in the solar system. “Jupiter was the most influential planet in the formation of the solar system,” said Miguel. Its gravitational pull helped shape the size and orbits of its cosmic neighbors, and so determining how it came about has important knock-on effects for other planets, he added. The findings also suggest a potential planetesimal origin for the other gas giants in the solar system: Saturn, Uranus and Neptune.
Other gaseous worlds in other star systems may also have formed by devouring planetesimals rather than pebbles, meaning they may also have a higher metallicity than their appearance suggests. It is therefore important that when we find these new worlds, which are being surveyed using NASA James Webb Telescopewe don’t judge them by their hazy skins, the researchers said.
The study was published online June 8 in the journal Astronomy and Astrophysics (opens in new tab).
Originally published on Live Science.