Ablation Hollow

  • Nicolas MangoldEmail author
  • Henrik Hargitai
Living reference work entry
DOI: https://doi.org/10.1007/978-1-4614-9213-9_1-1

Keywords

Impact Crater Cottage Cheese Closed Depression Rough Texture Covered Terrain 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Definition

A closed depression inferred to be carved by melting or sublimation of ice from an ice-bearing unit.

Category

Synonyms

Description

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).

Morphometry

From millimeter to tens of kilometers in width, from millimeter to hundreds of meters in depth. Pits studied by Fisher et al. (2002) in the northern ice cap of Mars are tens of meters wide and 1–2 m deep (Fisher et al. 2002).

Subtypes

  1. (1)
    Ablation hollows (pitted terrain) on snow/frost/ice covered terrain.
    1. (1.1)

      “Cottage cheese terrain” resembling cottage cheese at MOC resolution, on the north polar residual cap, Mars (Figs. 1, 2, 3, and 4)

       
    2. (1.2)

      “Swiss cheese terrain” (Mars): hollows in the south polar cap of Mars due to sublimation of carbonic ice (“South Polar Residual Cap Features”)

       
     
  2. (2)

    Impact craters’ melt sheets can display ablation hollows from volatile loss of melted silicates (“Hollows (Mercury)”).

     

Interpretation

Closed depressions often related to any volatile loss. Clear interpretation when terrains known to be ice rich (glaciers, polar caps, icy satellites).

Formation Models

  1. (1)

    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.

     
  2. (2)

    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”).

     
Fig. 1

Low-latitude (7°N) pitted terrain similar to ablation hollows in Mojave crater floor, Mars (Mangold 2011). Pits are 10 m wide. Scale bar 500 m. HiRISE PSP_009076_1880 (NASA/JPL/Univ. of Arizona)

Fig. 2

Decameter-scale pits in the north polar layered terrain of Mars near 86.9°N, 207.5°W. Scale bar 200 m. MOC CAL-00433 (NASA/JPL/MSSS)

Fig. 3

Mars north polar layered terrain rugged buttes near 86.7°N 238.7°W. Scale bar 200 m. MOC M00-02476 (NASA/JPL/MSSS)

Fig. 4

Ablation hollows formed by sublimation and wind lifting, in the process of erasing a crater (“Ghost Crater”) near 88.0°N, 135.0°E (Mangold 2011). Scale bar 50 m. HiRISE PSP_001406_2680 (NASA/JPL/Univ. of Arizona)

Age

From several 100 Ma on mid-latitude glaciers to active hollows on south polar cap on Mars.

Surface/Structural Units

Various ice-rich terrains, from icy crust to glaciers and polar caps, as well as impact crater melt sheets.

Composition

Usually from water ice, can exist from CO2 ice as on Mars southern cap.

Studied Locations

Mars polar terrains, glaciers.

Prominent Examples

  1. (1)

    Northern residual cap of Mars (Malin, Edgett 2001), north polar layered deposits composed of dust and ice (Milkovich and Head 2006)

     
  2. (2)

    Mottled terrain of Comet 19P/Borrelly (Britt et al. 2004)

     

Distribution

Prominent in ice-rich terrains submitted to strong temperature variations.

Significance

Presence of volatile in the subsurface.

Astrobiological Significance

If melting is involved, it could be interesting for recent active layer and possibility of present life on Mars.

Terrestrial Analog

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

First described on Mars as hectometer wide pits in ice-rich mid-latitude terrains (Squyres 1989) and at higher resolution as decameter-scale pits or rugged buttes (Malin and Edgett 2001).

Origin of Term

The texture is “popularly called cottage cheese terrain” (Fisher et al. 2002).

See Also

References

  1. Britt DT, Boice DC, Buratti BJ, Campins H, Nelson RM (2004) The morphology and surface processes of Comet 19/P Borrelly. Icarus 167:45–53. doi:10.1016/j.icarus.2003.09.004CrossRefGoogle Scholar
  2. Fisher DA, Winebrenner DP, Stern H (2002) Lineations on the “white” accumulation areas of the residual northern ice cap of Mars: their relation to the “accublation” and ice flow hypothesis. Icarus 159(1):39–52CrossRefGoogle Scholar
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  4. Mangold N (2011) Ice sublimation as a geomorphic process: a planetary perspective. Geomorphology 126:1–17CrossRefGoogle Scholar
  5. Milkovich SM, Head JW III (2006) Surface textures of Mars’ north polar layered deposits: a framework for interpretation and future exploration. Mars 2:21–45. doi:10.1555/mars.2006.0003CrossRefGoogle Scholar
  6. 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
  7. Squyres SW (1989) Urey prize lecture: water on Mars. Icarus 79:229–288CrossRefGoogle Scholar
  8. Thomas PC, Malin MC, Edgett KS, Carr MH, Hartmann WK, Ingersoll AP, James PB, Soderblom LA, Veverka J, Sullivan R (2000) North-south geological differences between the residual polar caps on Mars. Nature 404:161–164CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Laboratoire de Planétologie et Géodynamique de NantesUniversité de Nantes/CNRS UMR6112NantesFrance
  2. 2.Planetary Science Research GroupInstitute of Geography and Earth Sciences, Eötvös Loránd UniversityBudapestHungary