Jupiter Appears to Have Cannibalized Baby Planets as It Grew

Helium and hydrogen make up virtually all of Jupiter. The quantities of each roughly match their predicted counterparts in the early solar nebula.

However, it also includes other, heavier elements that astronomers refer to as metals. Although metals make up a very minor portion of Jupiter, their presence and distribution reveal a great deal to scientists.

A recent research suggests that Jupiter's metal distribution and composition indicate that the planet consumed several rocky planetesimals during its early evolution.

Our knowledge of Jupiter's genesis and evolution has changed significantly since NASA's Juno mission arrived at Jupiter in July 2016 and began collecting extensive data.

The Gravity Science instrument is one of the mission's characteristics. Between Juno and the Deep Space Network on Earth, radio signals are exchanged back and forth.

The method monitors Jupiter's gravitational field and provides more information about the planet's makeup.

Jupiter began to develop by absorbing rocky material. The solar nebula's gas began to accumulate quickly after that, and after many millions of years, Jupiter grew to its current size.

But there's a big question mark over the early stages of rocky accretion. Did it gather bigger rocks, such as planetesimals? Or did it accumulate rocks the size of pebbles? The time scales on which Jupiter originated varied depending on the response.

That question was the focus of a recent research. It appears in the journal Astronomy and Astrophysics with the title "Jupiter's inhomogeneous envelope inhomogeneous envelope". Yamila Miguel, an assistant professor of astrophysics at The Netherlands Institute for Space Research and the Leiden Observatory, is the primary author.

Thanks to the JunoCam on the Juno spacecraft, we're becoming used to seeing magnificent pictures of Jupiter. However, everything we perceive is merely superficial. Only the thin 50 kilometers (31 miles) outermost layer of the planet's atmosphere can be seen in all those mesmerizing pictures of the clouds and storms. 

The atmosphere of Jupiter, which extends hundreds of kilometers into space, contains the secret to the planet's birth and development.

Jupiter is generally acknowledged to be the Solar System's oldest planet. But researchers are interested in how long it took to form. The goal of the paper's authors was to use Juno's Gravity Science experiment to examine the metals in the planet's atmosphere.

Understanding Jupiter's creation heavily relies on the existence and distribution of pebbles in the planet's atmosphere, which was studied by the Gravity Science experiment.

There was no accurate information on Jupiter's gravity harmonics prior to Juno and its Gravity Science mission.

The scientists discovered that Jupiter's atmosphere isn't uniform as previously believed. Near the planet's core, metals are more abundant than in other layers. The total mass of the metals ranges from 11 to 30 Earth masses.

The researchers built models of Jupiter's interior dynamics using the data they had."In this paper, we assemble the most comprehensive and diverse collection of Jupiter interior models to date and use it to study the distribution of heavy elements in the planet's envelope," the authors write.

Two groups of models were produced by the group. The first collection consists of 3-layer models, and the second set includes dilute-core models.

"There are two mechanisms for a gas giant like Jupiter to acquire metals during its formation: through the accretion of small pebbles or larger planetesimals," stated lead author Miguel.

"We know that once a baby planet is big enough, it starts pushing out pebbles. The richness of metals inside Jupiter that we see now is impossible to achieve before that. So we can exclude the scenario with only pebbles as solids during Jupiter's formation. Planetesimals are too big to be blocked, so they must have played a role." 

With increasing distance from the core, metal richness in Jupiter's interior declines. That denotes the absence of convection, which scientists had assumed existed in the planet's deep atmosphere.

"Earlier, we thought that Jupiter has convection, like boiling water, making it completely mixed," noted Miguel. "But our finding shows differently."

"We robustly demonstrate that the heavy element abundance is not homogeneous in Jupiter's envelope," the authors write in their paper. "Our results imply that Jupiter continued to accrete heavy elements in large amounts while its hydrogen-helium envelope was growing, contrary to predictions based on the pebble-isolation mass in its simplest incarnation, favoring instead planetesimal-based or more complex hybrid models."

The authors come to the further conclusion that even when Jupiter was still young and heated, it did not mix through convection after it formed.

The study of gaseous exoplanets and efforts to ascertain their metallicity are also affected by the team's findings."Our result … provides a base example for exoplanets: a non-homogeneous envelope implies that the metallicity observed is a lower limit to the planet bulk metallicity."

In Jupiter's instance, it was impossible to tell from a distance whether it was metallic or not. The metallicity could only be indirectly measured once Juno landed. "Therefore, metallicities inferred from remote atmospheric observations in exoplanets might not represent the bulk metallicity of the planet."

Measuring exoplanet atmospheres and figuring out their composition will be one of the James Webb Space Telescope's first science activities. This study demonstrates that the data Webb offers could not accurately reflect what's happening in the deepest layers of massive gas planets.

This article was originally published by Universe Today. Read the original article.