Jupiter is composed almost entirely of hydrogen and helium. Their respective quantities correspond closely to theoretical quantities in the primordial solar nebula. But it also contains other, heavier elements, which astronomers call metals. Although minerals are a small part of Jupiter, their presence and distribution tells astronomers a lot.
According to a new study, the mineral content and its distribution on Jupiter means that the planet ate a lot of rocky young planets in its youth.
Since NASA’s Juno spacecraft arrived at Jupiter in July 2016 and began collecting detailed data, it has changed our understanding of Jupiter’s formation and evolution. One of the mission’s features is the Gravity Science tool. It sends radio signals back and forth between Juno and Earth’s deep space network. The process measures Jupiter’s gravitational field and tells researchers more about the formation of the planet.
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When Jupiter formed, it began accumulating rocky material. This was followed by a period of rapid gaseous accumulation from the solar nebula, and after millions of years, Jupiter became the giant it is today. But there is an important question regarding the initial period of rock accretion. Did you collect larger clumps of rock like minor planets? Or did it accumulate a pebble-sized substance? Depending on the answer, Jupiter formed on different time scales.
A new study has begun to answer this question. Titled “Jupiter’s Inhomogeneous Mantle,” it was published in the Journal of Astronomy and Astrophysics. The lead author is Yamila Miguel, associate professor of astrophysics at the Leiden Observatory and the Netherlands Institute for Space Research.
We are increasingly accustomed to the wonderful images of Jupiter thanks to the JunoCam of the Juno spacecraft. But what we see is only skin deep. All those charming images of clouds and storms are just the outer 50 kilometers (31 miles) of the planet’s atmosphere. The key to Jupiter’s formation and evolution is buried deep in the planet’s atmosphere, which is tens of thousands of kilometers deep.
It is widely accepted that Jupiter is the oldest planet in the solar system. But scientists want to know how long the formation took. The authors of the paper wanted to find minerals in the planet’s atmosphere using the Juno Gravitational Science Experiment. The presence and distribution of pebbles in the planet’s atmosphere plays a key role in understanding the formation of Jupiter, and the gravity science experiment measured the dispersion of pebbles throughout the atmosphere. Prior to Juno and its gravitational science experiment, there was no accurate data on Jupiter’s gravitational harmonics.
The researchers found that Jupiter’s atmosphere is not as homogeneous as previously thought. There are more minerals near the center of the planet than in the other layers. Altogether, the minerals add between 11 and 30 Earth masses.
With the data in hand, the team built models of Jupiter’s internal dynamics. “In this paper, we compile the most comprehensive and diverse set of internal models of Jupiter to date and use them to study the distribution of heavy elements in the planet’s atmosphere,” they wrote.
The team created two sets of models. The first group is three-layer models and the second is models with a reduced core.
“There are two mechanisms for a gas giant like Jupiter to obtain minerals during its formation: through the accretion of small pebbles or large minor planets,” said lead author Miguel. “We know that once a small planet gets big enough, it starts ejecting pebbles. The mineral richness within Jupiter that we see now would be impossible to achieve before that. So we can rule out the scenario using only pebbles as a solid during Jupiter formation. Small planets are larger than Being banned, so it must have played a role.”
The abundance of minerals in Jupiter’s interior decreases with distance from the center. This indicates a lack of convection in the deep atmosphere of the planet, which scientists thought was present. “Earlier, we thought Jupiter had a heat transfer, like boiling water, which makes it quite mixed,” Miguel said. “But our findings appear differently.”
“We strongly demonstrate that the abundances of the heavy element are not homogeneous in Jupiter’s shell,” the authors wrote in their paper. “Our results indicate that Jupiter continued to accumulate heavy elements in large quantities while its hydrogen and helium atmosphere was growing, contrary to predictions based on the sequestration mass of pebbles in its simplest incarnation, preferring instead Earth-based models or more complex hybrid models.”
The authors also concluded that Jupiter did not mix with convection after it formed, even when it was still young and hot.
The team’s findings also extend to the study of gaseous exoplanets and efforts to determine their metallicity. “Our result…provides a basic example of an exoplanet: the heterogeneous envelope indicates that the observed metallicity is a lower bound on the metallicity of the planet’s metallic mass.”
In Jupiter’s case, there was no way to determine its metallicity from a distance. Only when Juno arrived were scientists able to measure metallicity indirectly. “Therefore, the metallic elements inferred from distant atmospheric observations in exoplanets may not represent the planet’s mineral mass.”
When the James Webb Space Telescope begins scientific operations, one of its tasks is to measure the atmospheres of exoplanets and determine their composition. As this work shows, the data that Webb provides may not capture what’s going on in the deep layers of gas giant planets.