Astronomers believe they have identified the largest impact structure in the Solar System. By combining previous observations, scientists from Japan found that the Jovian moon Ganymede experienced a catastrophic impact event in the past.
The evidence for this is a series of ancients troughs on the surface of the moon. These geological formations are distributed concentrically across most of Ganymede. For the scientists, this is proof they were created by a single massive impact. The research is published in the journal Icarus.
The troughs are present on about 35 percent of the moon’s surface, which implies the impact crater has a radius of up to 7,800 kilometers (4,800 miles). The team estimates the body that created it would have been at least 50 kilometers (30 miles) wide, but more likely it was three times more.
Ganymede was recently studied by the Juno mission currently orbiting Jupiter, but detailed images of the moon’s surface are decades older. They were obtained by NASA’s Voyager 1, Voyager 2, and Galileo spacecraft. Researchers can’t be certain that the bullseye-like structure was created by an impact. However, it might be possible to find out by early next decade. At the end of the 2020s, we are going back to Jupiter to gain in-depth observations of the major Jovian moons.
“The European Space Agency’s JUICE (Jupiter Icy Moon Explorer) mission, scheduled to launch in 2022 and arrive in 2029, will examine Jupiter and its moons, including Ganymede, with instruments such as the GAnymede Laser Altimeter (GALA) which NAOJ is helping to develop and imaging spectrographs," lead researcher Naoyuki Hirata comments said in a statement.
"GALA is being developed mainly by the German Aerospace Center in collaboration with institutes in Switzerland, Spain, and Japan, including JAXA, Chiba Institute of Technology, Osaka University, and NAOJ. We hope that JUICE will confirm the results of this study and further advance our understanding of the formation and evolution of Jupiter’s moons.”
Ganymede is not only the largest moon of Jupiter but also the largest of all known moons. It is bigger than the planet Mercury, making it the 9th largest object in the Solar System.