Key takeaways

  • Scientists have found what they believe to be the largest impact crater in the solar system on Ganymede, Jupiter’s largest moon.
  • Reanalysis of data from past NASA missions shows that furrows on Ganymede’s surface suggest a massive impact that affected the entire moon.
  • The proposed impact was likely caused by a large asteroid, possibly up to 90 miles (150 kilometers) across, creating rings and fractures that formed the observed furrows.
  • The potential impact scar on Ganymede has a radius of up to 4,800 miles (7,800 kilometers), dwarfing the current largest known crater, Valhalla, on another of Jupiter’s moons, Callisto.
  • The European Space Agency’s JUICE mission, launching in 2022 and arriving in 2029, will further study Ganymede, Callisto, and Europa to gain more insights into these findings.
An artist’s depiction of Jupiter, at left, and its massive moon Ganymede in the foreground. (Image credit: Tsunehiko Kato, 4D2U Project, NAOJ)

Scientists believe they have discovered the largest impact crater in the solar system, with scars covering much of Jupiter’s largest moon, Ganymede.

The scientists behind the current study wanted to revisit observations from a number of previous NASA missions that investigated the enormous moon, which is larger than Mercury, the smallest planet in our vicinity. They were particularly captivated by a group of landforms known as furrows, which exist on some of the moon’s oldest topography.

Previous studies had identified these furrows as evidence of a huge impact powerful enough to leave scars across the whole surface of Ganymede. However, after examining the structures, the experts behind the new research feel this is an underestimate, and that the furrows imply an impact powerful enough to influence the entire moon.

The researchers began by collecting data from NASA’s twin Voyager missions, which sailed past the Jupiter system in 1979, as well as NASA’s Galileo mission, which studied the enormous planet and its neighbors for eight years in the late 1990s and early 2000s.

The scientists then reanalyzed observations from the Dark Terrain, which includes Ganymede’s earliest surfaces. According to the new modeling, all furrows in the Dark Terrain ripple out from the same location, including those on the opposite side of the moon.

The researchers propose that the furrows are signs of an impact event that affected all of Ganymede, rather than only the one hemisphere previously reported as being modified in such an event, albeit positively identifying an impact site requires more than suspicious rings.

However, if an impact was to blame, a large asteroid — at least 30 miles (50 kilometers) across and possibly more like 90 miles (150 kilometers) across — could have been involved in the collision, leaving a bullseye series of rings and fractures across the moon that, after millennia of geological processes, have become the furrows and troughs scientists see today, according to a statement about the new research.

If that modeling is true, the scientists claim to have discovered the greatest impact scar in the solar system, with a radius of up to 4,800 miles (7,800 kilometers) – over twice the length of the Mississippi River. The current greatest known impact system, called Valhalla Crater and discovered on another Jupiter moon, Callisto, pales in comparison, with a radius of 1,200 miles (1,900 km).

The researchers behind the latest study hope that the new data will allow them to better evaluate Ganymede’s furrows and comprehend what caused them. The European Space Agency is developing a spacecraft dubbed the Jupiter Icy Moons Explorer (JUICE), which is scheduled to launch in 2022. The expedition will concentrate on Ganymede, Callisto, and Europa, arriving in the area in 2029 and remaining for at least three years.

The research is described in a study published in the journal Icarus.

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