Peculiar texture of highlatitude groundicerich terrains

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Peculiar texture of high-latitudeground-ice-rich
terrains

• M. A. Kreslavsky and J. W. Head
• Brown University
• Kharkov Astronomical Institute

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• Kreslavsky and Head 2000Smoothing at high
  latitudes (MOLA data) Mantling (MOC
  images) ? ? High-latitude deposits
• Malin and Edgett 2001 MOC images ?
  High-latitude young mantle
• Mustard et al. 2001Dissection in 30-60?
  latitude zones (MOC images) ? ? Ice-rich
  deposits
• Kreslavsky and Head 2002Synthesis ? Ice-rich
  high-latitude mantle
• Tokar et al. 2002Merging with GRS/NS/HEND data

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MOC NA image
E02/01380
210 W 61 N
500 m
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High-Latitude Mantle Morphology

• very smooth (10s-100s m scale)
• characteristic texture (10 m scale)
• affected by topography (100s m - km scale)
• affected by latitude
• very homogeneous
• a few meters thick
• layered structure
• mechanically strong
• eroded at steep slopes
• dissected / eroded at lower latitudes (lt60)

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basketball
wrinkle
Typical mantle textures
1 km
regular
polygonal
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Latitudinal distribution of mantle textures
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MOC NA image
E04/00537
86 W 69 N
1 km
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MOC NA image
E04/00537
86 W 69 N
1 km
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MOC NA image
E04/00537
86 W 69 N
1 km
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MOC NA image
E04/00537
86 W 69 N
1 km
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MOC NA image
150 W 69 N
M02/01316
500 m
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MOC NA image
150 W 69 N
M02/01316
500 m
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High-Latitude Mantle Morphology

• very smooth (10s-100s m scale)
• characteristic texture (10 m scale)
• affected by topography (100s m - km scale)
• affected by latitude
• very homogeneous
• a few meters thick
• layered structure
• eroded at steep slopes
• dissected / eroded at lower latitudes (lt60)
• mechanically strong

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MOC NA image
E02/00398
79 W 74 N
500 m
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High-Latitude Mantle Icy

• HEND / NS / GRS data
• high ice content at depth (1 m scale)
• low ice content near the surface
• Has mechanical strength
• Extent agrees with subsurface ice stability
• Erosion - on steep slopes - at low latitudes
• Analogy with patterned ground in terrestrial
  permafrost regions

High-Latitude Mantle Indurated

• No erosion of the ice-free upper layer

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MOC NA image
E02/00123
218 W 79 N
500 m
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MOC NA image
210 W 60 N
E02/01380
1 km
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E02/01984
E02/00200
139 W 51 N
135 W 65 N
1 km
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Latitudinal distribution of pits and craters
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High-Latitude Mantle Crater Retention Age

• 0.3 - 10 Ma lower latitudes
• lt0.1 Ma higher latitudes
• Crater retention age uncertainty
• rescaling of cratering rate from lunar record
• extrapolation for younger ages
• poor statistics
• unknown atmospheric shielding
• Crater retention age difference
• deposition age difference
• persisting protecting ice sheet

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High-Latitude Mantle Mechanism of Formation

• Deposition of ice and dust
• desiccation and induration of upper layer
• Latest periods of high obliquity
• water vapor availability and mobility
• dust lifting
• extended subsurface ice stability zones
• Latest volcanic and/or water outflow episode

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Astronomical climate forcing
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Mantle deposition
NOT now NOT the last 0.4 Ma
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The most recent mantle deposition
30 0.4 Ma ? 34 0.6 Ma ? 40 4.1 Ma ? 45 gt
5 Ma ?
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Conclusions

• Detected by HEND high H concentration at high
  latitudes is due to specific deposit ice-rich
  mantle
• The mantle is geologically young(0.5-10 Ma ?)
• Complex history of deposition - alteration -
  removal