Under the picturesque outer layer of the gas giant hides a shell that is invisible to us. And in that shell, things go a little differently than expected.

This is suggested by a new study, conducted by an international team of scientists led by Yamila Miguel, who works at the Netherlands Institute for Space Research (SRON). Observations from spacecraft Juno — the only one able to see right through Jupiter’s scenic outer layer — hint, the researchers say, that the gases in Jupiter’s atmosphere — against all odds — are not uniformly distributed. For example, the inner part of that atmosphere (which is closer to the core of the planet) appears to contain much more ‘metals’ (elements heavier than hydrogen and helium) than the outer layer.

Surprising

“That’s very surprising,” Miguel tells Scientias.nl† “Because the planet transports energy and heat from the innermost layers to the outermost layers, this was believed to be done planetwide through convection.” You are undoubtedly familiar with that process – convection; it regularly takes place on your induction plate, among other things. For example when you boil eggs. The water at the bottom of the pan heats up first and rises, while the colder water at the top moves downwards. This creates a circular movement. The moment you add something to that pan – for example a coloring agent – ​​you will see that these convection-induced movements ensure that it quickly spreads homogeneously over the pan. “Similarly, convection would have mixed the materials in the planet Jupiter’s shell,” Miguel explains. “But our results show something different and show that Jupiter is not – as previously thought – using this mode of energy transport everywhere.” For the gases in Jupiter’s shell are thus not uniformly distributed; the heavier elements are better represented in the inner layer than in the outer layer.

Juno

As stated, the researchers draw that conclusion based on observations from space probe Juno. The probe has been investigating Jupiter since 2016 and is designed to discover what lies beneath the gas giant’s visible, glittering outer layer. “Juno has an orbit specifically designed to – by measuring the gravitational field over different locations – give us a better understanding of how mass is distributed across the planet and thus give us a better idea of ​​the planet’s internal structure, explains Miguel.

Formation

Juno not only reveals that Jupiter is not uniform, but also allows researchers to determine how many metals Jupiter’s shell contains in total. Added together, the metals in the planet’s invisible shell make up 11 to 30 times the weight of the Earth, Miguel and colleagues write in the magazine. Astronomy & Astrophysics† And that too is valuable information, because it gives more insight into how Jupiter formed. For example, the wealth of metals within Jupiter suggests that it was formed not from small stones, but from kilometer-sized boulders. “Some scientists think that Jupiter (and gas giants in general) forms because small space rocks (on the order of centimeters) clump or collide,” Miguel says. “However, we know that once a baby planet is big enough, it will push the small rocks away and only grow by attracting gas. As a result, the gaseous shell contains very few heavy elements. However, there are also those who think that large objects (on the order of kilometers) formed the building blocks of Jupiter.” Those larger boulders (also called planetesimals) couldn’t have pushed the growing Jupiter away so easily. “And therefore, while Jupiter was collecting gas, they continued to fall on the planet, which in turn results in the shell being much richer in metals (elements other than hydrogen and helium, the main components of gas). What our results now show is that the amount and distribution of metals on the planet does not align with growth through small pebbles alone. Planetesimals must also have played a role in the formation of the planet.”

exoplanets

The findings not only give us more insight into how Jupiter works, Miguel thinks. “Our results show that the transport of energy is different than previously thought and that not only influences our view of Jupiter, but also hints that other gas giants do not have a homogeneous structure. And that in turn could have consequences for our understanding of all gas giants, including exoplanets. In view of the new knowledge and information that we will be acquiring through telescopes such as the James Webb Space Telescope, that insight could again be very important when we start to interpret the data collected by these telescopes.”

Even more secrets

Meanwhile, Jupiter also has a few things to hide. “Many unsolved mysteries remain,” Miguel says. “We still don’t know where Jupiter formed, how the planet migrated, what influence the planet had on the supply of water on Earth (by asteroids and comets, ed.) and we still don’t know how the core of Jupiter formed. puts the planet together.”

Juno may be able to help answer some of those questions, as NASA decided last year to extend the probe’s mission for a few more years. The probe should have rammed into Jupiter last summer, but since it is still functioning properly, the probe will continue to investigate Jupiter and its surroundings at least until September 2025. During that time, Juno will not only take a closer look at Jupiter, but will also skim past the tenuous rings of the gas giant and some of Jupiter’s moons.