Young Jupiter was smacked head-on by massive newborn planet

Young Jupiter was smacked head-on by massive newborn planet
A rendering shows the effect of a major impact on the core of a young Jupiter, as suggested by scientists at Rice and Sun Yat-sen universities. They say the collision about 4.5 billion years ago could explain surprising readings from NASA's Juno spacecraft. Credit: Shang-Fei Liu/Sun Yat-sen University

A colossal, head-on collision between Jupiter and a still-forming planet in the early solar system, about 4.5 billion years ago, could explain surprising readings from NASA's Juno spacecraft, according to a study this week in the journal Nature.

Astronomers from Rice University and China's Sun Yat-sen University say their head-on can explain Juno's previously puzzling gravitational readings, which suggest that Jupiter's core is less dense and more extended that expected.

"This is puzzling," said Rice astronomer and study co-author Andrea Isella. "It suggests that something happened that stirred up the core, and that's where the giant impact comes into play."

Isella said leading theories of planet formation suggest Jupiter began as a dense, rocky or icy planet that later gathered its thick atmosphere from the primordial disk of gas and dust that birthed our sun.

Isella said he was skeptical when study lead author Shang-Fei Liu first suggested the idea that the data could be explained by a giant impact that stirred Jupiter's core, mixing the dense contents of its core with less dense layers above. Liu, a former postdoctoral researcher in Isella's group, is now a member of the faculty at Sun Yat-sen in Zhuhai, China.

"It sounded very unlikely to me," Isella recalled, "like a one-in-a-trillion probability. But Shang-Fei convinced me, by shear calculation, that this was not so improbable."

The research team ran thousands of and found that a fast-growing Jupiter can have perturbed the orbits of nearby "planetary embryos," protoplanets that were in the early stages of planet formation.

Liu said the calculations included estimates of the probability of collisions under different scenarios and distribution of impact angles. In all cases, Liu and colleagues found there was at least a 40% chance that Jupiter would swallow a planetary embryo within its first few million years. In addition, Jupiter mass-produced "strong gravitational focusing" that made head-on collisions more common than grazing ones.

Isella said the collision scenario became even more compelling after Liu ran 3-D computer models that showed how a collision would affect Jupiter's core.

"Because it's dense, and it comes in with a lot of energy, the impactor would be like a bullet that goes through the atmosphere and hits the core head-on," Isella said. "Before impact, you have a very dense core, surrounded by atmosphere. The head-on impact spreads things out, diluting the core."

Impacts at a grazing angle could result in the impacting planet becoming gravitationally trapped and gradually sinking into Jupiter's core, and Liu said smaller planetary embryos about as massive as Earth would disintegrate in Jupiter's thick atmosphere.

"The only scenario that resulted in a core-density profile similar to what Juno measures today is a head-on impact with a planetary embryo about 10 times more massive than Earth," Liu said.

Young Jupiter was smacked head-on by massive newborn planet
An infrared color composite of Jupiter was created from images taken by NASA's New Horizons spacecraft in 2007. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center

Isella said the calculations suggest that even if this impact happened 4.5 billion years ago, "it could still take many, many billions of years for the heavy material to settle back down into a dense core under the circumstances suggested by the paper."

Isella, who is also a co-investigator on the Rice-based, NASA-funded CLEVER Planets project, said the study's implications reach beyond our solar system.

"There are astronomical observations of stars that might be explained by this kind of event," he said.

"This is still a new field, so the results are far from solid, but as some people have been looking for planets around distant stars, they sometimes see infrared emissions that disappear after a few years," Isella said. "One idea is that if you are looking at a star as two rocky collide head-on and shatter, you could create a cloud of dust that absorbs stellar light and reemits it. So, you kind of see a flash, in the sense that now you have this cloud of dust that emits light. And then after some time, the dust dissipates and that emission goes away."

The Juno mission was designed to help scientists better understand Jupiter's origin and evolution. The spacecraft, which launched in 2011, carries instruments to map Jupiter's gravitational and magnetic fields and probe the planet's deep, internal structure.

Additional co-authors of the study include Yasunori Hori of the Astrobiology Center of Japan, Simon Müller and Ravit Helled of the University of Zurich, Xiaochen Zheng of Tsinghua University in Beijing and Doug Lin of both the University of California, Santa Cruz, and Tsinghua University in Beijing.


Explore further

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More information: The formation of Jupiter's diluted core by a giant impact, Nature (2019). DOI: 10.1038/s41586-019-1470-2 , https://www.nature.com/articles/s41586-019-1470-2
Journal information: Nature

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Aug 14, 2019
The premise of a high impact into Jupiter's atmosphere and into its core seems highly probable, given that the early solar system was a "wild west" of accreting mass and planetary formation. As planets acquired more mass and grew larger, the chances of impacts from stray bodies into each one becomes even better. A bigger target, one might say.

Aug 14, 2019
A bigger target, one might say.
"Strong gravitational focusing", no maybes about it ...

Aug 15, 2019
Distances between 2 bodies is a factor to be considered before any possibility of impact due to gravity. The asteroid Oumuamua was too far from Earth to be a danger as an incoming projectile, but meteorites are infalling objects that are relatively easy to find. So far, humans have been lucky.

Aug 15, 2019
Cranks can't count. Both Jupiter and an impactor are tiny compared to the Solar System's volume.

Aug 15, 2019
""The only scenario that resulted in a core-density profile similar to what Juno measures today is a head-on impact with a planetary embryo about 10 times more massive than Earth," Liu said." Abstract: "a similar event may have also occurred for Saturn".

First off, amazing! I can sympathize with Isella's "WTF" (to use science language); he makes a good show in the video by the way, worth watching in my opinion.

Second, the embryo's would be about equal massed at the time give or take a factor 1-4, and goes a long way to explain why Jupiter/Saturn (unusually massive) and no super-Earths (at least Jupiter ate one).

Third, the timing is most likely coinciding with the gas giant growth (but I haven't read the paper yet). This reminds me of the updated system timeline data - the leftover formation material reset rock ages before 4.48 Ga [Fig. 2, robust U-Pb ages: https://arxiv.org...8825.pdf ] - the system was much cleared out early on.

Aug 15, 2019
Cranks can't count. Both Jupiter and an impactor are tiny compared to the Solar System's volume.


And non-cranks can't read crank in full (in my case even harder, I block them now - they are just too boring). But if the idea is that an early collision means Jupiter is large relative to the system, it isn't. The exponential decay in the clearing out process (see the ref in my earlier comment) is natural and the disk viscosity at the time gave the high rate.

As the dust cleared out (helped by decreasing collision frequency) the system saw "a phase change" to modern orbits; Jupiter hasn't seen a huge collision since the clearing out. So indeed, Jupiter is relatively small compared to the system volume (~ 10^-25 times smaller, by my estimate).

Aug 15, 2019
I finally got hold of the paper, the timing is after growth but before clearing out:

"Giant impacts are likely to occur shortly after runaway gas accretion when Jupiter's gravitational perturbation increases to about thirty-fold in a fraction of a million years, thus destabilizing the orbits of nearby planetary embryos. This transition follows oligarchic growth and the emergence of multiple embryos with isolation mass in excess of a few Earth masses, M⊕ (ref. 22). Some of these massive embryos may collide with the gas giant during their orbit crossing. ... As a result, in a large fraction of these numerical tests an embryo could collide with Jupiter within a few million years, that is, within the lifetime of the Solar nebula. Of those catastrophic events, head-on collisions are more common than grazing ones owing to Jupiter's gravitational focusing effects."

Aug 15, 2019
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Aug 15, 2019
meteorites are infalling objects that are relatively easy to find.


really? good luck with that.

Aug 15, 2019
meteorites are infalling objects that are relatively easy to find.


really? good luck with that.
says Shootist

It is helpful to know a little something about Geology so that you don't pick up a dried cow turd thinking that it's a meteorite. They are in many places (the meteorites, I mean) and many times can be recognised by how coming through the Earths atmosphere has melted them (very little sharpness to them).

I am starting to wonder about Torbjorn's mental state, as he has blocked many commenters and their opinion on scientific matters. I doubt that he knew of my position on the nonexistence of 'time', since he could not have read of it. He has blocked me also. Not that I care, but it seems to be a sign of a form of Dementia to block opinions no matter the reason. Or is he just stiff-necked?

Personally, I prefer geodes where, if cut in half, the crystals inside are worth the effort.

Aug 15, 2019

Personally, I prefer geodes where, if cut in half, the crystals inside are worth the effort.


So go cut yourself in half and see if anything useful pops out. Even if it doesn't, you'll have done humanity a favour.

Aug 16, 2019
oh jeebus castro
what will crawl out of that?
will horrify Humanity!

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