Space crash: New research suggests huge asteroid shifted Jupiter's moon Ganymede on its axis

The solar system's largest moon, Ganymede, which orbits the largest planet, Jupiter, was hit by an asteroid four billion years ago that shifted the gas giant's satellite on its axis, new research suggests.

The asteroid was about 20 times larger than the Chicxulub asteroid, which is thought to have ended the dinosaurs' reign on Earth, estimates Naoyuki Hirata, a planetologist at Kobe University in Hyogo, Japan, in the Sept. 3 issue of the journal "Scientific Reports."

Ganymede, which is 50% larger than our own moon, has an ocean beneath its icy surface – up to 60 miles deep – and is suspected of being able to support primitive life.

The moon is also interesting because of the "tectonic troughs" or furrows seen on its surface. These furrows form concentric circles around the site of a likely asteroid collision, Hirata says in an explanation of the research on the Kobe University website.

Scientists have long pondered how big the asteroid might have been. Hirata took a clue from the fact that the the resulting crater always faces away from Jupiter. He also knew that findings from the New Horizons space probe supported the idea the one-time planet Pluto had also shifted on its rotational axis in the past.

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The impact of a large asteroid – Hirata's computer simulations suggest the asteroid measured 186 miles in diameter – could cause the moon to shift to its current position, he suggests. The resulting crater would have been 870 miles to nearly 1,000 miles in diameter, before material began settling in it, he said.

“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," Hirata said. "I believe that further research applying the internal evolution of ice moons could be carried out next."

There may be other explanations for the impact site, but “this is a neat attempt to rewind the clock via computer simulations, searching for an explanation for the distribution of scars across Ganymede," Leigh Fletcher, a planetary scientist at the University of Leicester, told The Guardian.

The European Space Agency's Jupiter Icy Moons Explorer (Juice) is amid its voyage to Jupiter with a scheduled 2031 arrival to study Ganymede and Jupiter's other moons, Callisto and Europa.  

"Future explorations – in particular, the Juice, plans to obtain the gravity and topographic data – will reveal a remnant of topographic profiles or gravity anomalies associated with the furrow-forming impact and the reorientation of Ganymede, which would provide insights into this giant impact and Ganymede's early history," Hirata told Newsweek.

Contributing: Doyle Rice.

Follow Mike Snider on X and Threads: @mikesnider & mikegsnider.

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