This article is based on an article from the Japanese edition of Engadget and was created using the translation tool Deepl.
On July 27, 2020, a research team consisting of Kobe University, National Institute of Technology, Oshima College in Yamaguchi Prefecture, and the National Astronomical Observatory of Japan (NAOJ) announced the discovery of a giant crater with a diameter of 15,600 km on the surface of Jupiter's moon Ganymede.
With a diameter of 5,726 km, Ganymede is the largest satellite in the solar system, larger than Mercury (with a diameter of 4,900 km), and its exact size was determined by observations by the Voyager 1 and 2 spacecraft in 1979 and 1980. Close observations of Jupiter by the Galileo spacecraft from 1995 to 2003 showed the existence of a magnetic field, and later studies showed that there were oceans underground.
These studies have revealed that the Ganymede surface is composed of darker areas of older geological features and lighter areas of newer geological features, and the presence of characteristic furrow-shaped features called "Furrow" in the darker areas has been confirmed.
The research team from Kobe University and Oshima College hoped that the Furrow would provide clues about the birth and evolution of Jupiter's satellites and the history of the entire solar system. They studied images taken by Voyager 1 and Voyager 2 and the Galileo spacecraft, and found that the Farrow is a multiple ring crater that extends across Ganymede's surface.
Multiple ring craters are concentric ring craters that form when a gigantic object, such as an asteroid, hits the surface. In the past, Callisto, Jupiter's fourth moon, discovered a huge multiple ring crater, named Valhalla Basin, with a diameter of about 3,800 kilometers. However, Ganymede's multiple ring craters are an order of magnitude larger than those of Callisto's Valhalla Basin.
The team also conducted impact simulations using a "computational server" operated by the National Astronomical Observatory of Japan (NAOJ) to investigate how the craters were created. As a result, the team concluded that the size and structure of the crater could be explained if an asteroid with a radius of about 150 kilometers collided with it at a speed of 20 kilometers per second. They also said that this collision is thought to have occurred more than 4 billion years ago.
Incidentally, it is believed that an asteroid with a "diameter" of 10-12 km created the Vredefort Dome, the largest crater on Earth with a diameter of about 190 km.
Ganymede's interior is thought to contain layers of rock, iron and ice, which the team speculates may have been formed by the heat generated by a major celestial impact.
In the 2030s, the European Space Agency plans to explore Ganymede with the Jupiter Icy moons Explorer (JUICE) mission. In this exploration, the plan is to investigate the topography of Ganymede in detail using a laser altimeter, which NAOJ is participating in the development of. We expect that this survey will reveal the detailed structure of the multiple ring craters discovered in this study.
This article is based on an article from the Japanese edition of Engadget and was created using the translation tool Deepl. The Japanese edition of Engadget does not guarantee the accuracy or reliability of this article.