Memphis facula

Memphis Facula is a palimpsest, or "ghost crater", on Ganymede, the largest of the Jovian satellites.

Some 340 km across, it is situated in the south western part of Galileo Regio, a huge almost circular dark region on Ganymede's north eastern flank. Although almost level today, it is a relic of a massive impact and once was a deep impact crater whose walls have slumped and its floor has risen isostatically, smoothing out the remaining topograpohy with slush.

The morphology of the larger palimpsests like Memphis Facula suggests that Ganymedes icy crust at the time of impact was about 10 km thick and was penetrated by the impact, allowing the slush and fluid beneath to fill and level out the crater.

A Voyager 2 image of Memphis Facula on Ganymede (white patch on lower right)

References

1. Harland, D. M.; Jupiter Odyssey, Springer Praxis (2000), p. 136