20x bigger than dinosaur-killer asteroid strike shifted axis of Jupiter’s largest moon

Roughly four billion years ago, a cataclysmic event shaped the largest moon in our solar system. This was the time when an asteroid smashed with Jupiter’s moon Ganymede.

According to a new study from Japan’s Kobe University, this impact was so powerful that it shifted the moon’s axis.

This asteroid was 20 times larger than the one that wiped out the dinosaurs from our planet.

Simulations helped draw conclusion

Jupiter’s moon Ganymede is a remarkable celestial body, generating its own magnetic field and harboring liquid water. And it’s so large, that it even outsizes the planet Mercury.

Ganymede’s tidal locking means one side always faces Jupiter, while the other side remains perpetually hidden. Moreover, large parts of its surface have distinctive tectonic troughs known as furrows.

Reportedly, these are thought to be the oldest features of Ganymede — resemble the scars of a massive impact that slammed early in the moon’s history. Some of these concentric rings span up to 7,800 kilometers (4,847 miles) across the surface.

“The Jupiter moons Io, Europa, Ganymede, and Callisto all have interesting individual characteristics, but the one that caught my attention was these furrows on Ganymede,” said Hirata Naoyuki, the Kobe University planetologist.

He added: “We know that this feature was created by an asteroid impact about 4 billion years ago, but we were unsure how big this impact was and what effect it had on the moon.”

The earlier study, done by Hirata and his colleagues, examined images captured by the Voyager probes in 1979 and the Galileo orbiter between 1995 and 2003.

As per the press release , Hirata was the “first to realize that the location of an asteroid impact on Ganymede is almost precisely on the meridian farthest away from Jupiter.”

In this new study, the author compared the impact event on Ganymede to a similar event on Pluto.

The New Horizons mission previously discovered that a huge collision forced Pluto’s rotational axis to tilt. Based on these parallels, Hirata concluded that Ganymede’s impact had a similar effect, causing its axis to shift.

Hirata used his experience in modeling impact events to evaluate the magnitude and force of the asteroid that impacted Ganymede. Through computer simulations, he estimated the impactor’s size.

Asteroid with diameter of 300 km

The asteroid that impacted Ganymede had a diameter of around 300 kilometers, making it nearly 20 times bigger than the dinosaur one [around 6.2 miles (10 kilometers) in diameter].

Furthermore, it generated a large “transient crater” that was 870 to 994 miles (1,400 to 1,600 kilometers) broad.

The models indicate that only a huge collision could have changed Ganymede’s axis. The location of the impact on the far side of the moon aligned with the direction of this shift, providing strong evidence for the connection between the two events.

“I want to understand the origin and evolution of Ganymede and other Jupiter moons. The giant impact must have had a significant impact on the early evolution of Ganymede, but the thermal and structural effects of the impact on the interior of Ganymede have not yet been investigated at all. I believe that further research applying the internal evolution of ice moons could be carried out next,” explained Hirata.

The European Space Agency’s JUICE space probe will help to unravel the mysteries of Ganymede’s past.

The space probe is set to explore Ganymede in 2034, aiming to uncover the moon’s secrets through six months of intensive observation.

Interestingly, the potential presence of subsurface liquid water oceans on Ganymede makes it a prime candidate for harboring alien life.

The findings were reported in the journal Scientific Reports.