NAOJ/CfCA: That Must've Hurt -- Ganymede Covered by Giant Crater

[bystander]

That Must’ve Hurt: Ganymede Covered by Giant Crater
National Astronomical Observatory of Japan | Center for Computational Astrophysics | 2020 Aug 13

Jupiter (background, left) and its moon Ganymede (foreground, right) visualized using the Four-Dimensional Digital Universe viewer “Mitaka.” The furrows found on the older, Dark Terrain, areas of Ganymede’s surface could actually be parts of a single, giant, multiring impact crater. (Credit: Tsunehiko Kato, 4D2U Project, NAOJ)

---

Researchers from Kobe University and the National Institute of Technology, Oshima College have investigated the orientation and distribution of the ancient tectonic troughs on Jupiter’s moon Ganymede through a detailed reanalysis of image data from probe missions. They discovered that these troughs are distributed concentrically across almost the entire surface of Ganymede, indicating that these troughs may be part of one giant crater covering Ganymede. If so, this is the largest impact structure identified in the Solar System so far.

Many furrows, or trough formations, have been observed on the surface of Ganymede, one of the Jovian moons. This research group comprehensively reanalyzed image data of Ganymede obtained by NASA’s Voyager 1, Voyager 2, and Galileo spacecrafts. The results revealed that almost all of these furrows appear to be arranged in concentric rings centered around a single point, indicating that this global multiring structure may be the remains of a giant crater. The radial extent of the multiring structures measured along Ganymede’s surface is 7800 km. For comparison, the mean circumference of Ganymede is only 16,530 km. If correct, this is the largest crater yet identified in the Solar System. The previous record holder with a 1900 km radius is on Calisto, another Jovian moon.

Based on a computer simulation conducted using “PC Cluster” at the National Astronomical Observatory of Japan (NAOJ), the team speculates that Ganymede’s giant crater could have resulted from the impact of an asteroid with a radius of 150 km traveling 20 km/s. ...

A Global System of Furrows on Ganymede Indicative of Their Creation
in a Single Impact Event ~ Naoyuki Hirata, Ryo Suetsugu, Keiji Ohtsukia

• Icarus 352:113941 (Dec 2020) DOI: 10.1016/j.icarus.2020.113941

[neufer]

A true color image of Ganymede acquired by the Galileo spacecraft

---

Ganymede rolling a hoop on a vase (Attic red-figure krater, 500–490 B.C.E.)

---

<<Galileo Regio is a large, dark surface feature on Jupiter's moon Ganymede. It is a region of ancient dark material that has been broken apart by tectonism and is now surrounded by younger, brighter material (such as that of Uruk Sulcus) that has been upwelling from Ganymede's interior. It is thought to be some 4 billion years old and is heavily cratered and palimpsested, but also has a unique distribution of furrows and smooth terrain that has been the subject of conflicting speculation regarding cause or origin. The distribution of smooth terrain on Galileo Regio suggests that the ancient crust of Ganymede was relatively thin in the equatorial region and thickened poleward in this area. The age relationships, morphology, and geometry of the furrow systems do not favor an origin by impact or tidal stressing. A possible, but speculative, origin is crustal uplift caused by a plume-like convection cell in a fluid mantle underlying a thin crust. Stratigraphic and morphologic relationships among furrows and crater palimpsests suggest that palimpsest morphology is largely the result of impact into a rheologically weak crust rather than viscous relaxation.

The regio is bounded on the southwest by Uruk Sulcus, which lies between it and Marius Regio. Within Galileo Regio itself lies the palimpsest Memphis Facula, a relic of an impact crater that has been flattened in a manner characteristic of some of the Solar System bodies with icy crusts.>>