Jupiter’s Moon Ganymede Struck by Ancient Asteroid Larger Than Dinosaur-Killing Rock

Jupiter’s Moon Ganymede Struck by Ancient Asteroid Larger Than Dinosaur-Killing Rock 

Small mauve moon next to swirling planetary mass

The largest moon in the solar system, Jupiter’s Ganymede, was hammered by an ancient asteroid vastly larger than the one that wiped out the dinosaurs, according to new research. This colossal impact, which occurred around 4 billion years ago, may have had a dramatic effect on the moon, causing it to reorient itself such that the impact crater now faces away from Jupiter.

The Scale of the Impact

Scientists have determined that the asteroid that struck Ganymede was about 185 miles in diameter, making it about 20 times larger than the asteroid responsible for the extinction event on Earth. This impact created a crater up to 1,000 miles wide. The initial crater was partly filled with debris that fell back to the moon's surface after the collision.

Dr. Naoyuki Hirata, a planetary scientist at Kobe University in Japan, led the research, which was published in Scientific Reports. Hirata's study builds on earlier observations of Ganymede's surface, which is marked by distinctive furrows believed to be the remnants of this colossal impact.

Impact Effects on Ganymede

The research utilized computer simulations to explore the aftermath of the impact. These simulations suggest that the force of the collision caused Ganymede to spin such that the impact crater now faces almost directly away from Jupiter. This reorientation could be attributed to the redistribution of mass caused by the asteroid strike.

Ganymede, which is larger than Mercury, would have experienced a dramatic transformation from this impact. The collision not only removed the original surface but also likely affected the moon’s interior. Scientists believe Ganymede harbors a hidden saltwater ocean beneath its icy crust, and this impact could have had significant implications for its geological and potentially even its astrobiological history.

Future Investigations

Dr. Hirata acknowledges that while the asteroid impact theory is compelling, alternative explanations cannot be entirely ruled out. Further evidence might come from the European Space Agency’s JUpiter ICy moons Explorer (JUICE) mission. Launched last year, JUICE is tasked with exploring Jupiter and its moons, including Ganymede. The spacecraft is equipped to capture high-resolution images of the moon’s surface and analyze its gravity field and shape, which could offer new insights into the impact and its consequences.

Prof. Leigh Fletcher from the University of Leicester notes that the ancient terrains of Jupiter’s moons bear witness to billions of years of cosmic bombardment. “Making sense of all those overlapping events on satellite surfaces is challenging,” he said. “This is a neat attempt to rewind the clock via computer simulations.”

JUICE’s mission will be crucial in testing Hirata’s hypothesis by providing detailed observations of Ganymede’s surface and internal structure. The findings could shed light on the moon’s geological history and its evolution over billions of years.

Significance of the Research

This study enhances our understanding of the early solar system’s dynamics and the impacts that shaped celestial bodies. As we continue to explore these distant worlds, each new discovery helps piece together the history of our solar system and the forces that have sculpted its largest moons.


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