Around 4 billion years ago, an asteroid hit the Jupiter moon Ganymede, causing its axis to shift. This impact was around 20 times larger than the one that led to the extinction of dinosaurs on Earth. Ganymede is the largest moon in the Solar System, bigger than even the planet Mercury, and is known for its liquid water oceans beneath its icy surface. The moon is tidally locked, always showing the same side to the planet it orbits, and researchers have observed furrows on its surface believed to be the result of a major impact event.
Kobe University planetologist, Naoyuki Hirata, became interested in the furrows on Ganymede and set out to determine the size of the asteroid impact that caused them. By analyzing the impact’s location on the moon’s surface, he was able to calculate that the asteroid was likely around 300 kilometers in diameter and created a transient crater between 1,400 and 1,600 kilometers in diameter. These findings were published in the journal Scientific Reports, shedding light on the significant impact this event had on Ganymede’s early evolution.
Hirata’s simulations showed that only an impact of this size could have caused the mass distribution changes necessary for the moon’s rotational axis to shift. He hopes to further investigate the thermal and structural effects of the impact on Ganymede’s interior, as well as the implications for the other Jupiter moons. The ESA’s JUICE space probe is set to arrive at Ganymede in 2034, providing valuable data that could help answer some of these questions.
The research was funded by the Japan Society for the Promotion of Science and the Hyogo Science and Technology Association. This study opens up new avenues for understanding the origin and evolution of Ganymede and the other Jupiter moons. By studying the internal evolution of ice moons, researchers hope to gain a deeper understanding of the impact events that have shaped these celestial bodies throughout history.
Ganymede’s unique characteristics, such as its subsurface oceans, make it a fascinating subject of study for planetary scientists. The impact event that affected the moon’s axis remains a key point of interest, as it offers insights into the moon’s early history and evolution. Hirata’s research has provided valuable data on the size and impact of the asteroid that hit Ganymede, paving the way for further investigations and discoveries in the field.
Overall, this study highlights the importance of impact events in shaping planetary bodies and offers a glimpse into Ganymede’s past. The asteroid impact that shifted the moon’s axis was a significant event that has left a lasting imprint on Ganymede’s surface and internal structure. As researchers continue to explore this moon and other celestial bodies in the Solar System, new discoveries and insights are likely to emerge, deepening our understanding of the universe and its complex history.