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.

A possible, but speculative, origin is crustal uplift caused by a plume-like convection cell in a fluid mantle underlying a thin crust.

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.

A study from 2020 by Hirata, Suetsugu and Ohtsuki suggests that Ganymede probably was hit by a massive asteroid 4 billion years ago; an impact so violent that may have shifted the moon's axis.