Flooded Terrain in Terra Sabaea (MULTISPECTRUM; credits: Lunexit)

Two distinctly different terrain types are visible in this image of the Northern Lowlands of Mars: an older, heavily cratered landscape has been inundated by much younger flows.
The valley floors are filled with flows that have relatively smooth surfaces and very few superposed impact craters.

In contrast, the mesas and hills making up the older terrain have blocky surfaces, perhaps fragmented by ancient impacts.