KeywordsImpact Crater Cottage Cheese Closed Depression Rough Texture Covered Terrain
A closed depression inferred to be carved by melting or sublimation of ice from an ice-bearing unit.
A type of sublimation landform.
Closely spaced depressions with similar shapes, in the residual polar cap of Mars producing a gentle hummocky pitted surface (Fisher et al. 2002). This terrain displays a rough topography of pits, cracks, and some knobs (Thomas et al. 2000). Pits joined in roughly linear strings or depressions with preferential direction form lineations (Fisher et al. 2002).
- (1)Ablation hollows (pitted terrain) on snow/frost/ice covered terrain.
Impact craters’ melt sheets can display ablation hollows from volatile loss of melted silicates (“Hollows (Mercury)”).
Closed depressions often related to any volatile loss. Clear interpretation when terrains known to be ice rich (glaciers, polar caps, icy satellites).
Dry ablation by radiant heating: the hollows deepen as their base receives more reflected light than the ridges that surround them. In the presence of dust, the summer sublimation creates a residual lag of dust. During the ice sublimation process, dust particles retreat tangential to the ablating surface, resulting in a concentration of dust particles on the ridges of the ablation hollows. If the dust layer on the ridges is thin, it absorbs solar radiation and ablation is faster on the ridges than in the hollows, producing a less pronounced topography. If the layer of dust is thick, dust functions as an insulating layer and the ridges ablate slower than the hollows, producing a more pronounced topography (Milkovich and Head 2006). Dust may be later removed by strong polar winds without melting. This process resurfaces the Martian polar cap fast as inferred from the lack of impact craters.
Ablation by melting and evaporation or flow: more common on Earth, producing carved suncups and rough texture. This process generates various landforms on glaciers (moulins, supraglacial channels) (“Glaciofluvial Valley”).
From several 100 Ma on mid-latitude glaciers to active hollows on south polar cap on Mars.
Various ice-rich terrains, from icy crust to glaciers and polar caps, as well as impact crater melt sheets.
Usually from water ice, can exist from CO2 ice as on Mars southern cap.
Mars polar terrains, glaciers.
Prominent in ice-rich terrains submitted to strong temperature variations.
Presence of volatile in the subsurface.
If melting is involved, it could be interesting for recent active layer and possibility of present life on Mars.
Suncups, networks of polygonal, cuspate hollows with relief of 2–50 cm, observed on melting snow or ice (e.g., surface melting of glaciers). An individual pit is termed suncup, ablation hollow, and ablation polygon; the rough texture produced by adjacent pits is called honeycombed snow. Its extreme variant is penitent ice/snow, in which ridges and pits are enhanced into spikes and troughs (Rhodes et al. 1987).
History of Investigation
Origin of Term
The texture is “popularly called cottage cheese terrain” (Fisher et al. 2002).
- Rhodes JJ, Armstrong RL, Warren SG (1987) Mode of formation of “ablation hollows” controlled by dirt content of snow. J Glaciol 33(114):135–139Google Scholar