Named after the Greek river god; father of Callirrhoe, Ganymede's mother.
Achelous is a fresh crater on Ganymede adjacent to the similarly sized Gula. It has an outer lobate ejecta deposit extending about a crater radius from the rim. A characteristic feature of both craters, almost identical in size, is the "pedestal" - an outward-facing, gently sloped scarp that terminates the continuous ejecta blanket. Similar features may be seen in ejecta blankets of Martian craters, suggesting impacts into a volatile rich target material. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Ganymede they are named after gods and heroes of ancient Fertile Crescent people.
Image Source. Marker locations are approximate and may not always appear to align with image on map.