An ancient asteroid is now believed to have hit Jupiter’s moon Ganymede, causing it to shift on its axis 4 billion years ago. The wild part? The asteroid happens to be 20 times larger than the one that wiped out dinosaurs.
A recent study explored the impacts that could have created the system of furrows on Jupiter’s moon. Ganymede is the largest moon in the solar system—even bigger than the planet Mercury. It’s also covered in large, deep furrows that apparently form a pattern around a single spot on the moon’s surface. According to astronomers, this might be due to a major asteroid impact.
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“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 Naoyuki Hirata, assistant professor of planetology at Kobe University in Japan. “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.”
Hirata believes the discovery of this ancient asteroid impact is “meaningful” as it sheds light on what could have shifted Ganymede’s orientation. Such an impact can create gravity anomalies that change how a planet rotates.
According to Hirata’s equations, the asteroid was likely about 186 miles wide—25% the size of Jupiter’s moon and 20 times larger than the one that led to the extinction of dinosaurs on Earth. Additionally, it created a crater around 870 to 994 miles in diameter.
“I want to understand the origin and evolution of Ganymede and other Jupiter moons,” said Hirata. “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.”
