In the transition zone, nestled between maces, this image shows the valley floor where eroded rocky and or soil debris appears to have flowed viscously from the mace of walls across the valley to merge. A leading theory is that ice and snow became entrained with the soil debris as it shed from the mace. This combined ice-rich debris then flowed slowly downhill. Rock glaciers on Earth are an analogous landform that float viscously like a glacier lubricated by ice trapped in the poor-shaped spaces. This image shows light-toned viscous debris that overlays a darker-toned surface. Both surfaces sport irregular fracture patterns, an evidence that substantial erosion has since taken place. The upper viscous flow surface also contains abundant, small, regular, polygonal patterns. Such patterns are commonplace in permafrost on Earth, and are typically considered strong evidence for shallow, subsurface ice. Erosion and the formation of small scarps reveal a multitude of layers within the subsurface. Such structure is unusual for a single glacial flow, and may indicate episodic glacial advance and retreat. Additionally, the sparse population of rocks on the surface, and along the eroded scarps, suggest that the debris eroding from the maces can sys largely of soil.