That’s gonna sting.

Astro­bi­ol­o­gy Cen­ter, Japan

NASA’s Juno space­craft has giv­en us unre­al views of the gas giant Jupiter. But Juno isn’t just a mem­ber of the inter­plan­e­tary paparazzi, it’s a ful­ly capa­ble cos­mic lab with instru­ments designed to probe the mam­moth plan­et. After tak­ing pre­cise mea­sure­ments of Jupiter’s grav­i­ta­tion­al field, the space­craft has dis­cov­ered that the plan­et’s core isn’t as dense as expect­ed.

Now, sci­en­tists have pro­posed an almost-apoc­a­lyp­tic rea­son for this: A “plan­e­tary embryo” with 10 times more mass than Earth (and almost as much mass as Uranus) could have slammed into the largest plan­et in the solar sys­tem and dis­turbed its core. It’s not the object that whacked Jupiter last week and was cap­tured by an ama­teur astronomer on Earth. This event would have tak­en place in the dis­tant past, and we’re only just learn­ing how it may have shaped Jupiter.

The research, pub­lished Wednes­day in the jour­nal Nature, details a num­ber of sim­u­la­tions demon­strat­ing how a plan­e­tary embryo could have led to the uneven dis­tri­b­u­tion of heavy met­als we see through­out Jupiter’s gaseous enve­lope today. Jupiter is most­ly com­posed of hydro­gen and heli­um gas­es that move around a dense core. Sci­en­tists believed that heavy met­als should be con­fined close to a dense core, but the Juno mis­sion revealed that the met­als are actu­al­ly strewn fur­ther from the core, mak­ing it more dilute.

“Jupiter’s inte­ri­or mod­els based on Juno’s data sug­gest Jupiter has a fuzzy core that extends to almost half of its radius, which no one has ever imag­ined,” says Shangfei Liu, lead author on the study and astronomer at Sun Yat-sen Uni­ver­si­ty in Chi­na.

How could that occur? The research team’s sim­u­la­tions sug­gest the young Jupiter suf­fered a giant impact dur­ing its for­ma­tive years, which gave rise to this weird, unex­pect­ed dis­tri­b­u­tion.

Now play­ing: Watch this: NASA video gives a Juno’s-eye view of the approach to… 2:58

Though the col­li­sion sounds vio­lent, it’s almost as if the young Jupiter swal­lowed up the plan­e­tary embryo. “A plan­e­tary embryo is a still-form­ing pro­to­plan­et, most­ly made of rock and ice from the solar neb­u­la,” explains Liu. The sim­u­la­tions show that the core of the pro­to­plan­et would have had to col­lide with Jupiter’s core to throw up the heavy ele­ments and mix them through­out the entire enve­lope. The mod­els show that the impact would have result­ed in the inter­nal struc­ture dis­cov­ered by NASA’s Juno and in the heavy ele­ment dis­tri­b­u­tion.

Oth­er sim­u­la­tions demon­strate that if the small­er plan­et only skipped across Jupiter, the col­li­sion would­n’t have the pow­er to redis­trib­ute heavy met­als through­out the gaseous enve­lope (though it would still be bad news for the baby plan­et).

Slight­ly bruised and bro­ken; from our head on col­li­sion.

Astro­bi­ol­o­gy Cen­ter, Japan

These mod­els also offer an expla­na­tion for some of the phe­nom­e­na seen in a num­ber of eas­i­ly-dis­cov­er­able exo­plan­ets, the plan­ets that lie out­side our solar sys­tem. A num­ber of these plan­ets, known as “hot Jupiters,” are super dense, stacked with heavy ele­ments and orbit very close to their star. They’re also prone to giant impacts. The researchers sug­gest their mod­el might explain why there are so many heavy met­als in these hot Jupiters, since they get smashed by plan­e­tary embryos as they form.

Could a series of small events, rather than one huge impact, give rise to the Jupiter we see today? The researchers say this needs more inves­ti­ga­tion.

The work pro­vides fur­ther evi­dence of the tumul­tuous envi­ron­ment of the ear­ly solar sys­tem. Pre­vi­ous research sug­gests that mas­sive impacts shaped our moon and Earth itself. The new research even sug­gests Sat­urn may have expe­ri­enced a sim­i­lar impact event dur­ing its for­ma­tion and anoth­er NASA probe, Cassi­ni, famous­ly plunged into the plan­et’s inte­ri­or in 2017.

“There are stud­ies using Cassini’s data (espe­cial­ly dur­ing its grand finale) to mod­el Sat­urn’s inte­ri­or,” says Liu. “But Juno was designed to mea­sure Jupiter’s grav­i­ty field, so the data is much bet­ter and mod­els are more reli­able. But Sat­urn’s inte­ri­or is def­i­nite­ly worth to look at in the future.”

As for Juno? The Jov­ian explor­er has been orbit­ing Jupiter since 2016 and recent­ly had its mis­sion extend­ed to 2022, so we can expect more rev­e­la­tions ahead.

Space geeks tweak NASA images of Jupiter’s red spot 20 Pho­tos

Orig­i­nal­ly pub­lished Aug. 14, 10:15 a.m. PT.

Update, Aug. 15 at 3:57 p.m.: Adds com­ments from Shangfei Liu.

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