A surface treatment robot includes a chassis having forward and rear ends and a drive system carried by the chassis. The drive system includes right and left driven wheels and is configured to maneuver the robot over a cleaning surface. The robot includes a vacuum assembly, a collection volume, a supply volume, an applicator, and a wetting element, each carried by the chassis. The wetting element engages the cleaning surface to distribute a cleaning liquid applied to the surface by the applicator. The wetting element distributes the cleaning liquid along at least a portion of the cleaning surface when the robot is driven in a forward direction. The wetting element is arranged substantially forward of a transverse axis defined by the right and left driven wheels, and the wetting element slidably supports at least about ten percent of the mass of the robot above the cleaning surface.