The Utopia basin is estimated to have formed around 4.3-4.1 billion years ago.[6][7] The impactor was likely around 400–700 kilometres (250–430 mi) in diameter.[8][9][10] The basin was subsequently mostly filled in, resulting in a mascon (a strong positive gravity anomaly) detectable by orbiting satellites.[11][12]
Many rocks at Utopia Planitia appear perched, as if wind removed much of the soil at their bases.[13][14] A hard surface crust is formed by solutions of minerals moving up through soil and evaporating at the surface.[15] Some areas of the surface exhibit scalloped topography, a surface that looks like it was carved out by an ice cream scoop. This surface is thought to have formed by the degradation of an ice-rich permafrost.[16] Many features that look like pingos on the Earth are found in Utopia Planitia (~35–50° N; ~80–115° E).[17]
On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior.[18][19][20]
Utopia Planitia Scalloped terrain led to the discovery of a large amount of underground ice enough water to fill Lake Superior[18][19][20]
Martian terrain
Map of terrain
Scalloped topography is common in the mid-latitudes of Mars, between 45° and 60° north and south. It is particularly prominent in the region of Utopia Planitia[21][22] in the northern hemisphere and in the region of Peneus and Amphitrites Patera[23][24] in the southern hemisphere. Such topography consists of shallow, rimless depressions with scalloped edges, commonly referred to as scalloped depressions or simply scallops. Scalloped depressions can be isolated or clustered and sometimes seem to coalesce. A typical scalloped depression displays a gentle equator-facing slope and a steeper pole-facing scarp. This topographic asymmetry is probably due to differences in insolation. Scalloped depressions are believed to form from the removal of subsurface material, possibly interstitial ice, by sublimation. This process may still be happening at present.[25]
Scalloped ground, as seen by HiRISE under HiWish program. A study published in Icarus found that the landforms of scalloped topography can be made by the subsurface loss of water ice by sublimation under current Martian climate conditions. Their model predicts similar shapes when the ground has large amounts of pure ice, up to many tens of meters in depth.[26]
Close up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.
Scalloped ground, as seen by HiRISE under HiWish program.
Close-up of scalloped ground, as seen by HiRISE under HiWish program. Surface is divided into polygons; these forms are common where ground freezes and thaws. Note: this is an enlargement of a previous image.
Pedestal crater, as seen by HiRISE under HiWish program The ejecta is not symmetrical around crater because the asteroid came at a low angle out of the North East. The ejecta protected the underlying material from erosion; hence the crater looks elevated. The location is Casius quadrangle.
Close-up of East side (right side) of previous image of pedestal crater showing polygons on lobe. Since the margin of the crater has lobes and polygons, it is believed there is ice under the protective top. Picture taken with HiRISE under HiWish program. Note: this is an enlargement of the previous image.
Polygonal, patterned ground is quite common in some regions of Mars.[27][28][29][30][31][32] It is commonly believed to be caused by the sublimation of ice from the ground. Sublimation is the direct change of solid ice to a gas. This is similar to what happens to dry ice on the Earth. Places on Mars that display polygonal ground may indicate where future colonists can find water ice. Patterned ground forms in a mantle layer, called latitude dependent mantle, that fell from the sky when the climate was different.[33][34][35][36]
High center polygons, shown with arrows, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
Scalloped terrain labeled with both low center polygons and high center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
Low center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
High and low center polygons, as seen by HiRISE under HiWish program. Location is Casius quadrangle. Image enlarged with HiView.
Other features in Utopia Planitia
MOLA map showing boundaries for Utopia Planitia and other regions
Holes and hollows on crater floor in Utopia Planitia, as seen by HiRISE under HiWIsh program. These shapes may have resulted from ice leaving the ground.
Glacier on a crater floor, as seen by HiRISE under HiWish program. The cracks in the glacier may be crevasses. There is also a gully system on the crater wall.
Layered mesa, as seen by HiRISE under HiWish program
Context for next image of layers along Hrad Vallis, as seen by CTX. Photo labeled with layers, streamlined forms, and arrow indicating direction water flowed.
Layers exposed along Hrad Vallis, as seen by HiRISE under HiWish program
^ abMcGill, G. E. (1989-03-10). "Buried topography of Utopia, Mars: Persistence of a giant impact depression". Journal of Geophysical Research. 94: 2753–2759. Bibcode:1989JGR....94.2753M. doi:10.1029/JB094iB03p02753.
^Mutch, T. et al. 1976. "The Surface of Mars: The View from the Viking 2 Lander". Science: 194. 1277–1283.
^Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. New York.
^Arvidson, R. A. Binder, and K. Jones. 1976. "The Surface of Mars". Scientific American: 238. 76–89.
^Sejourne, A. et al. 2012. Evidence of an eolian ice-rich and stratified permafrost in Utopia Planitia, Mars. Icarus. 60:248–254.
^Soare, E., et al. 2019.
Possible (closed system) pingo and ice-wedge/thermokarst complexes at the mid latitudes of Utopia Planitia, Mars. Icarus. doi:10.1016/j.icarus.2019.03.010
^Dundas, C., S. Bryrne, A. McEwen. 2015. Modeling the development of martian sublimation thermokarst landforms. Icarus: 262, 154-169.
^Kostama, V.-P., M. Kreslavsky, Head, J. 2006. Recent high-latitude icy mantle
in the northern plains of Mars: Characteristics and ages of emplacement.
Geophys. Res. Lett. 33 (L11201). doi:10.1029/2006GL025946.
^Malin, M., Edgett, K. 2001. Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruise through primary mission. J. Geophys. Res. 106 (E10),
23429–23540.
^Milliken, R., et al. 2003. Viscous flow features on the surface
of Mars: Observations from high-resolution Mars Orbiter Camera (MOC)
images. J. Geophys. Res. 108 (E6). doi:10.1029/2002JE002005.
^Mangold, N. 2005. High latitude patterned grounds on Mars: Classification,
distribution and climatic control. Icarus 174, 336–359.
^Kreslavsky, M., Head, J. 2000. Kilometer-scale roughness on Mars: Results from
MOLA data analysis. J. Geophys. Res. 105 (E11), 26695–26712.
^Seibert, N., J. Kargel. 2001. Small-scale martian polygonal terrain: Implications
for liquid surface water. Geophys. Res. Lett. 28 (5), 899–902.
S
^Hecht, M. 2002. Metastability of water on Mars. Icarus 156, 373–386
^Mustard, J., et al. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature 412 (6845), 411–414.
^Kreslavsky, M.A., Head, J.W., 2002. High-latitude Recent Surface Mantle on Mars:
New Results from MOLA and MOC. European Geophysical Society XXVII, Nice.
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![Scalloped ground, as seen by HiRISE under HiWish program. A study published in Icarus found that the landforms of scalloped topography can be made by the subsurface loss of water ice by sublimation under current Martian climate conditions. Their model predicts similar shapes when the ground has large amounts of pure ice, up to many tens of meters in depth.[26]](File:ESP_037461_2255scallopstop.jpg)
