While the massive atmosphere of Jupiter consists mainly of hydrogen and helium, the key to understanding the gas giant’s formation and evolution lies in the distribution of the remaining (heavy) elements.
“When NASA’s Juno spacecraft arrived at Jupiter in 2016, we caught a glimpse of the remarkable beauty of the biggest planet in our Solar System,” said Dr. Yamila Miguel, an astronomer at the SRON Netherlands Institute for Space Research and Leiden Observatory, and colleagues.
“Besides the famous Great Red Spot, Jupiter turns out to be littered with hurricanes, almost giving it the appearance and mystique of a Van Gogh painting.”
“The planet’s envelope underneath the thin visible layer however, is not immediately apparent.”
“Still, Juno is able to paint us a picture by sensing the gravitational pull above different locations on Jupiter.”
“This gives us information about the composition of the interior, which is not like what we see in the surface.”
“Instead, it has a higher content of ‘metals’ — elements heavier than hydrogen and helium — towards the center of the planet.”
To reach this conclusion, the astronomers built theoretical models that adhere to the observational constraints measured by Juno.
They studied the distribution of metals because it gives them information about how Jupiter was formed.
They found the inner part of the Jovian atmosphere has more metals than the outer parts.
Their results shows that the total mass of heavy elements varies between 11 and 30 Earth masses and the inner compact core of Jupiter has a mass of 7 Earth masses.
“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,” Dr. Miguel said.
“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.”
The findings mean that the abundance decreases outward with a gradient, instead there being a homogeneous mixing across the envelope.
“Earlier we thought that Jupiter has convection, like boiling water, making it completely mixed. But our finding shows differently,” Dr. Miguel said.
The study was published in the journal Astronomy & Astrophysics.
Y. Miguel et al. 2022. Jupiter’s inhomogeneous envelope. A&A 662, A18; doi: 10.1051/0004-6361/202243207
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