Scientists Find Remains of Cannibalized Baby Planets In Jupiter's Cloud-Covered Belly

Jupiter's innards are full of the remains of baby planets that the gas giant gobbled up as it expanded to become the behemoth we see today, scientists have found. The findings come from the first clear view of the chemistry beneath the planet's cloudy outer atmosphere. Space.com reports: In the new study, researchers were finally able to peer past Jupiter's obscuring cloud cover using gravitational data collected by NASA's Juno space probe. This data enabled the team to map out the rocky material at the core of the giant planet, which revealed a surprisingly high abundance of heavy elements. The chemical make-up suggests Jupiter devoured baby planets, or planetesimals, to fuel its expansive growth. [...] [T]he 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 accreted 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 enabled the team to map out slight variations in the planet's gravity, which helped them to see where the rocky material is located within the planet. The researcher's models revealed that there is an equivalent of between 11 and 30 Earth masses of heavy elements within Jupiter (3% to 9% of Jupiter's mass), which is much more than expected. The new models point to a planetesimal-gobbling origin for Jupiter because the pebble-accretion theory cannot explain such a high concentration of heavy elements. If Jupiter had initially formed from pebbles, the eventual onset 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 stopped additional pebbles from being pulled inside the planet. This curtailed rocky accretion phase would likely have given Jupiter a greatly reduced heavy metal abundance, or metallicity, than what the researchers calculated. However, planetesimals could have glommed onto Jupiter's core even after the gas accretion phase had begun; that's 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 within Jupiter, the researchers said. The study also revealed another interesting finding: Jupiter's insides do not mix well into its upper atmosphere, which goes against what scientists had previously expected. The new model of Jupiter's insides shows that the heavy elements the planet has absorbed have remained largely close to its core and the lower atmosphere. Researchers had assumed that convection mixed up Jupiter's atmosphere, so that hotter gas near the planet's core would rise to the outer atmosphere before cooling and falling back down; if this were the case, the heavy elements would be more evenly mixed 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 going on inside the gas giant's atmosphere. The researchers' findings could also change the origin stories for other planets in the solar system. The study was published in the journal Astronomy and Astrophysics.

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