Of particular interest are the relatively flat plains interspersed between the large craters (called, appropriately, intercrater
Images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about 5 to 7 centimeters apart on the intercrater
plains between Lahontan Crater and the Columbia Hills.
Scattered across the planet, the layered formations are common in such places as the impact craters of western Arabia Terra, the intercrater
plains of northern Terra Meridiani, and the chasms of the giant canyon Valles Marineris.
Widespread patches of smooth terrain, dubbed "intercrater
plains" after being spotted by Mariner 10, bear the hallmarks of ancient lava flows.
Wilhelms and most other lunar scientists of the time interpreted these light-hued intercrater plains as being volcanic in origin.
The origin of these intercrater plains may very well be fluidized basin ejecta, as proposed for the Cayley Plains.
The southeast quadrant is unusual in that the areas between the craters are smooth--if these intercrater plains (as geologists call them) were darker they would be considered mare.
Because Wilhelms's basin is probably the oldest one on the Moon, its impact ejecta have long since been covered by debris from other basins and cannot be the source of all the surrounding smooth intercrater plains.