The solar system’s largest moon, Ganymede, alongside Jupiter in a picture taken by NASA’s Cassini spacecraft
NASA/JPL/University of Arizona
A significant event that occurred billions of years ago might have drastically altered Ganymede, the largest moon of Jupiter.
Naoyuki Hirata and his team at Kobe University, Japan, delved into Ganymede’s intricate furrow system, a series of concentric troughs believed to be remnants of a massive impact structure in the outer solar system.
The researchers found that the centre of the furrow system closely aligns with Ganymede’s tidal axis, indicating that the impact responsible for the formation of the furrows caused a significant redistribution of mass that reoriented the moon.
Simulations conducted by the team suggested that the impacting object likely had a diameter of approximately 150 kilometres, much larger than the asteroid that led to the extinction of dinosaurs on Earth.
Andrew Dombard from the University of Illinois Chicago described that if a similar asteroid were to hit Earth, it would result in a catastrophic global event.
The impact would have pierced through Ganymede’s icy crust into its liquid oceans, creating a transient crater and dispersing vast amounts of material across the moon’s surface.
Following the impact, a thick layer of ejecta would have formed around the site, increasing the gravity in that region. Over time, this gravitational anomaly would have caused Ganymede to reorient itself, aligning the impact site with its tidal axis, as shown by the simulations.
Furrows on Ganymede are thought to be remnants of an ancient impact structure
NASA/JPL/Brown University
Hirata’s team drew parallels between this phenomenon and a similar event on Pluto, where a large impact resulted in the formation of a basin known as Sputnik Planitia, causing a reorientation of the dwarf planet.
However, determining the exact size of the impacting object on Ganymede is challenging due to the lack of comprehensive data on the moon’s gravity and topography, according to Hirata.
Dombard raised concerns about the model’s accuracy in accounting for Ganymede’s complex icy structure, stating that while the process depicted in the study is plausible, the specific numerical values may not be entirely reliable.
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