Epigeus is the largest known

impact crater An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...

on Jupiter's

Galilean satellite The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, and recognized by him as satellites of Jupiter ...

Ganymede, with a diameter of 343 km. It is 6.5% the mean equatorial diameter of Ganymede, . It is located in

Marius Regio Marius may refer to: People *Gaius Marius (157 BC-86 BC), Roman statesman, seven times consul. Arts and entertainment * ''Marius'' (play), a 1929 play by Marcel Pagnol * "Marius" (short story), a 1957 story by Poul Anderson * ''Marius'' (193 ...

at . At the center of Epigeus, there is a 25-km-radius region of sub-radial dark-floored troughs or fractures. These troughs range from approximately 150 to 250 m across, are generally linear, and merge in dendritic or

anastomosing An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be normal ...

patterns. The troughs exhibit two orthogonal preferred orientations, trending north–south and east–west. A bright, rough-textured, lobate deposit occupies the central 15 to 20 km of this region and locally surrounds troughs up to 25 km from the

palimpsest In textual studies, a palimpsest () is a manuscript page, either from a scroll or a book, from which the text has been scraped or washed off so that the page can be reused for another document. Parchment was made of lamb, calf, or kid skin an ...

center. This bright region consists of

massif In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...

s 200 to 300 m across separated by 200 to 300 m. The outer ring is a complex zone corresponding to a crater diameter. The zone between those two rings is relatively smooth and it is covered in small knobs. Several lobes of this unit appear to have flowed into

Valley A valley is an elongated low area often running between Hill, hills or Mountain, mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers ...

s within this outer ring zone. The smooth units in the center and between the inner and outer rings may be a solidified impact-melt sheet. Epigeus' basin is rich with ice deposits. Epigeus was named after the Phoenician god; this name was approved by the

International Astronomical Union The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreac ...

in 1997.

References

Impact craters on Ganymede (moon) {{Crater-stub