Jupiter Was Hit by Another Planet 4.5 Billion Years Ago in Colossal Collision That Fundamentally Altered Solar System's Gas Giant, Scientists Say

Jupiter may have been struck by a newborn planet in a colossal head-on collision 4.5 billon years ago that fundamentally altered the solar system's largest gas giant, according to a study published in the journal Nature.

An international team of researchers came to this conclusion after running numerous 3D computer simulations—and they say the finding could help to explain some puzzling measurements collected by the Juno spacecraft, which is currently orbiting the planet.

Data from the Juno mission has allowed scientists to create an accurate picture of Jupiter's gravitational field, which has been used to infer information about the planet's composition and internal structure.

However, these observations indicate that Jupiter's core is less dense and much larger than what scientists expected. In fact, the Juno data suggests that the planet has a diluted core containing heavy elements—those other than hydrogen or helium—which extends to nearly half of Jupiter's radius. This challenges standard planetary formation theories.

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

One possible explanation, according to the researchers, is that early Jupiter's initial compact core was gradually eroded over time, although this hypothesis contains a number of significant uncertainties

So instead the scientists propose that a head-on collision between a large, still-forming planet and the young Jupiter in the early stages of the solar system could have shattered the planet's initial dense core, causing the heavy elements to mix with its less dense outer layers.

Initially, Isella was skeptical of this idea when it was put forward by lead author of the study Shange-Fei Liu from Sun Yat-sen University in China—a former postdoctoral researcher at Rice.

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

The team then ran thousands of computer simulations which showed that this scenario could feasibly have taken place. However the only collision which could have produced the type of core that we see in Jupiter today would have been a head on strike with a planetary embryo that was about 10 times more massive than Earth.

"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."

The researchers say that the latest findings could have significant implications for our understanding of other phenomena in our universe.

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

"One idea is that if you are looking at a star as two rocky planets collide head-on and shatter, you could create a cloud of dust that absorbs stellar light and reemits it," he said. "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."

Juno launched from Cape Canaveral, Florida, on August 5, 2011, arriving at Jupiter in July 2016. So far it has completed several scientific flybys around the planet, providing fascinating insights into the gas giant's origins, structure, atmosphere and magnetic field.

In this time, the spacecraft Juno has revolutionized our understanding of the gas giant, revealing the secrets of its mega cyclone clusters and the vast depths of its great storm, among other discoveries.

Jupiter collision
An artist’s impression of a collision between a young Jupiter and a massive still-forming proto-planet in the early solar system. llustration by K. Suda & Y. Akimoto/Mabuchi Design Office, courtesy of Astrobiology Center, Japan