Science & Technology

Jupiter Was Smacked by a Baby Planet in Its Early History

Turns out Earth isn't the only planet that got smacked by a big object . Long ago, a small world slammed into mighty Jupiter, new measurements suggest. We can still see the echoes of this cosmic collision in our solar system's biggest planet.

Bumper Cars in Space

Our solar system was a shooting gallery 4.5 billion years ago, and new evidence from Jupiter suggests that it suffered a huge blow early in its history.

The giant of the solar system got a big shock, a new study says, when Jupiter slammed head-on into another planet that was still forming. The study recently appeared in Nature and was led by Shang-Fei Liu, a former postdoctoral researcher at Rice who is now a faculty member at Sun Yat-sen in Zhuhai, China. What's even stranger is we can still see evidence of that possible collision from spacecraft today. The Juno spacecraft — a fairly recent visitor from NASA — found that the core of Jupiter is larger and less dense than what mathematical calculations suggest.

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

While it sounds improbable, we have ample evidence suggesting something similar also happened elsewhere in the solar system — in fact, it happened to Earth. The leading theory for how our moon formed suggests that a Mars-sized object crashed into our planet early in the solar system's history. While the collision nearly annihilated Earth, our planet survived, and the fragments eventually coalesced into the moon we see today.

An artist’s impression of a collision between a young Jupiter and a massive still-forming protoplanet in the early solar system.

A History of Hard Hits

Clearly, the solar system used to be a more dangerous place before it settled into the more stable configuration of eight planets circling the sun that we know today. But it's not without its dangers: There still are asteroids, comets, and other small worlds orbiting in different directions than the planets, like a car hurtling the wrong way down a NASCAR track.

While civilization could be wiped out by some of these worlds, it's unlikely. That's because the biggest objects are already in stable orbits or have been destroyed or flung far away over the eons. (Another reason you shouldn't lose any sleep over civilization killers is that NASA hasn't found any after decades of searching. The agency and its partners are still scanning the skies today, just in case.)

Jupiter's and Earth's early chaotic histories were just one stage of the billiard ball environment that swept through the solar system. Roughly four billion years ago, what astronomers call the "late heavy bombardment" had swarms of small bodies pummeling the worlds in our solar system. Evidence on our world was swept away by wind, water, and volcanic erosion, but Earth's moon still carries the scars.

Most astronomers are confident that Jupiter's gravitational influence had a huge impact, sometimes literally, on how small worlds orbited in the solar system. In fact, the new study shows a 40 percent chance that Jupiter would tug a planet towards it in its first few million years — a signal of how strong its gravity is. Some astronomers even suggest that Jupiter steered planet-killing worlds away from Earth over billions of years, allowing life to form.

Get stories like this one in your inbox or your headphones: Sign up for our daily email and subscribe to the Curiosity Daily podcast.

Learn more about the residents of our solar system in "Solar System: An Exploration of the Bodies that Orbit the Sun" by Marcus Chown. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Elizabeth Howell August 16, 2019

Curiosity uses cookies to improve site performance, for analytics and for advertising. By continuing to use our site, you accept our use of cookies, our Privacy Policy and Terms of Use.