Inverted Topography (Natural Colors; credits for the additional process. and color.: Dr Paolo C. Fienga - Lunexit Team)

Caption NASA:"The system of sinuous ridges seen at the top of the image is the remnants of a channel system. In this case the channel has been filled by a material more resistant to erosion than the surroundings.
As the surround material was eroded away the resistant channel fill was left behind, forming a ridge where the channel had once been. This reversal of topography - from a channel to a ridge - is termed Inversion or Inverted Topography".