HiWish program - Revision history

Suitupshowup: /* Cracks/fractures */

2026-04-10T16:29:56Z

Cracks/fractures

Suitupshowup: /* Hollows */ added image

2026-04-10T16:19:59Z

Hollows: added image

Suitupshowup: /* Hollows */

2026-04-10T16:10:46Z

Hollows

Suitupshowup: /* Hollows */ added image

2026-04-10T16:05:46Z

Hollows: added image

Suitupshowup: /* Cracks/fractures */

2026-04-10T14:57:42Z

Cracks/fractures

Suitupshowup: /* Cracks/fractures */

2026-04-10T14:56:37Z

Cracks/fractures

Suitupshowup: /* High center pologons */ created a new section about cracks

2026-04-10T14:52:33Z

High center pologons: created a new section about cracks

Suitupshowup: /* High center pologon craters */

2026-04-10T12:25:20Z

High center pologon craters

Suitupshowup: /* Low center polygon craters */

2026-04-10T12:24:20Z

Low center polygon craters

Suitupshowup: /* High center pologon craters */

2026-04-09T15:49:56Z

High center pologon craters

← Older revision		Revision as of 16:29, 10 April 2026
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	==Cracks/fractures==		==Cracks/fractures==

−	Various features like hollows and ribbed terrain begin ~~wih~~ cracks. As time goes by the cracks enlarge becasue the extra surface area exposing more ground ice to go into the air by sublimation. Sublimation is when a solid goes directly to a gas without melting.	+	Various features like hollows and ribbed terrain begin with cracks. As time goes by the cracks enlarge becasue the extra surface area exposing more ground ice to go into the air by sublimation. Sublimation is when a solid goes directly to a gas without melting.

← Older revision		Revision as of 16:19, 10 April 2026
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	File:ESP 066765 2245ribslabeled.jpg\|How hollows are formed from cracks. Cracks expose more ground ice to the air; hence, more sublimation can take place, making the cracks larger and larger.		File:ESP 066765 2245ribslabeled.jpg\|How hollows are formed from cracks. Cracks expose more ground ice to the air; hence, more sublimation can take place, making the cracks larger and larger.
		+
		+	File:ESP 066765 2245 ribs labeledcropped.jpg\|Enlarged diagram of how hollows form starting with cracks.
	</gallery>		</gallery>

@@ Line 27: / Line 27: @@
 File:Close view of hollows created when ice left the ground.jpg|Close, color view of hollows.  The HiView program was used in the rgb color scheme.
-File:ESP 066765 2245ribslabeled.jpg|How hollows are formed from cracks.  Cracks expose more groung ice to the air; hence, more sublimation can take place, making the cracks larger and larger.
+File:ESP 066765 2245ribslabeled.jpg|How hollows are formed from cracks.  Cracks expose more ground ice to the air; hence, more sublimation can take place, making the cracks larger and larger.
 </gallery>

← Older revision		Revision as of 16:05, 10 April 2026
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	File:Close view of hollows created when ice left the ground.jpg\|Close, color view of hollows. The HiView program was used in the rgb color scheme.		File:Close view of hollows created when ice left the ground.jpg\|Close, color view of hollows. The HiView program was used in the rgb color scheme.

		+	File:ESP 066765 2245ribslabeled.jpg\|How hollows are formed from cracks. Cracks expose more groung ice to the air; hence, more sublimation can take place, making the cracks larger and larger.
	</gallery>		</gallery>

@@ Line 627: / Line 627: @@
 ==Cracks/fractures==
-Various features like hollows and ribbed terrain begin wih cracks.  As time goes by the cracks enlarge becasue the extra surface area exposed more ground ice to go into the air by sublimation.  Sublimation is when a solid goes directly to a gas without melting.
+Various features like hollows and ribbed terrain begin wih cracks.  As time goes by the cracks enlarge becasue the extra surface area exposing more ground ice to go into the air by sublimation.  Sublimation is when a solid goes directly to a gas without melting.
@@ Line 633: / Line 633: @@
 2215fractures.jpg|Fractures These fractures are believed to eventually turn into canyons because the cracks will get much larger when ice in the ground disappears into the thin Martian atmosphere and the remaining dust blows away.
 File:56968 2140cracks.jpg|Close view of cracks on crater floor, as seen by HiRISE under [[HiWish program]]

← Older revision		Revision as of 14:52, 10 April 2026
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	As ice or sand seasonally accumulates in the cracks (aggradation), the expanding wedges exert lateral pressure on the surrounding soil. This pressure forces the sediment upward along the edges of the polygon, creating elevated rims while the center remains relatively depressed. On Mars, these are often considered "young" or "active" features, indicating that ground ice is currently stable or accumulating. <ref>https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref>		As ice or sand seasonally accumulates in the cracks (aggradation), the expanding wedges exert lateral pressure on the surrounding soil. This pressure forces the sediment upward along the edges of the polygon, creating elevated rims while the center remains relatively depressed. On Mars, these are often considered "young" or "active" features, indicating that ground ice is currently stable or accumulating. <ref>https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref>
		+
		+	==Cracks/fractures==
		+
		+	Various features like hollows and ribbed terrain begin wih cracks. As time goes by the cracks enlarge becasue the extra surface area exposed more ground ice to go into the air by sublimation. Sublimation is when a solid goes directly to a gas without melting.
		+
		+
		+	<gallery class="center" widths="380px" heights="360px">
		+
		+	44322 2215fractures.jpg\|Fractures These fractures are believed to eventually turn into canyons because the cracks will get much larger when ice in the ground disappears into the thin Martian atmosphere and the remaining dust blows away.
		+
		+	ESP 046366 2215fractures.jpg\|Wide view of fractured ground, as seen by HiRISE under HiWish program Cracks form on the Martian surface, and then they turn into large fractures.
		+
		+	46366 2215fractures.jpg\|Close view of fractures from the previous image
		+
		+	File:ESP 056968 2140cracks.jpg\|Cracks on crater floor
		+
		+	File:56968 2140cracks.jpg\|Close view of cracks on crater floor, as seen by HiRISE under [[HiWish program]]
		+
		+
		+	File:ESP 057311 2125crackscraters.jpg\|Close view of cracks of various sizes Ice disappears along crack surfaces and makes crack larger. Note that small craters do not have very big rims; they may be just pits.
		+
		+	File:57311 2155crackssmallarge.jpg\|Close view of cracks of various sizes Ice disappears along crack surfaces and makes crack larger.
		+
		+	File:57311 2155crackscrater.jpg\|Cracks around crater, as seen by HiRISE under [[HiWish program]]
		+
		+	</gallery>
		+
		+

	==High center pologons==		==High center pologons==

@@ Line 625: / Line 625: @@
 As ice or sand seasonally accumulates in the cracks (aggradation), the expanding wedges exert lateral pressure on the surrounding soil.  This pressure forces the sediment upward along the edges of the polygon, creating elevated rims while the center remains relatively depressed.   On Mars, these are often considered "young" or "active" features, indicating that ground ice is currently stable or accumulating. <ref>https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref>
-==High center pologon craters==
+==High center pologons==
 The polygonal areas of Mars are geometric patterns found in the planet's mid-to-high latitudes. They give us clues  of past and present climate conditions. These features are similar to patterned ground in Earth's Arctic and Antarctic regions  The sometimes strange shapes  mostly form through a cycle of thermal contraction and subsequent cracking of ice-rich soil. <ref>Sako, T., Hasegawa, H., Ruj, T., Komatsu, G., & Sekine, Y. (2025). The periglacial landforms and estimated subsurface ice distribution in the northern mid-latitude of Mars. Journal of Geophysical Research: Planets, 130, e2023JE008232. https://doi.org/10.1029/2023JE008232</ref>

@@ Line 607: / Line 607: @@
         Defrosting dune--white areas still contain frost.  Frost is in low parts of polygons.
-==Low center polygon craters==
+==Low center polygons==
 The polygonal areas of Mars are geometric patterns found in the planet's mid-to-high latitudes. They give us clues  of past and present climate conditions. These features are similar to patterned ground in Earth's Arctic and Antarctic regions  The sometimes strange shapes  mostly form through a cycle of thermal contraction and subsequent cracking of ice-rich soil. <ref>Sako, T., Hasegawa, H., Ruj, T., Komatsu, G., & Sekine, Y. (2025). The periglacial landforms and estimated subsurface ice distribution in the northern mid-latitude of Mars. Journal of Geophysical Research: Planets, 130, e2023JE008232. https://doi.org/10.1029/2023JE008232</ref>

@@ Line 628: / Line 628: @@
 The polygonal areas of Mars are geometric patterns found in the planet's mid-to-high latitudes. They give us clues  of past and present climate conditions. These features are similar to patterned ground in Earth's Arctic and Antarctic regions  The sometimes strange shapes  mostly form through a cycle of thermal contraction and subsequent cracking of ice-rich soil. <ref>Sako, T., Hasegawa, H., Ruj, T., Komatsu, G., & Sekine, Y. (2025). The periglacial landforms and estimated subsurface ice distribution in the northern mid-latitude of Mars. Journal of Geophysical Research: Planets, 130, e2023JE008232. https://doi.org/10.1029/2023JE008232</ref>
-The initial formation of these polygons begins when sharp drops in temperature cause the permanently frozen ground (permafrost) to contract and fracture. Over time, these individual fractures connect into a vast network of hexagonal or pentagonal shapes. Once these cracks form, they can be filled by windblown sand, ice, or a combination of both, creating "wedges" that physically pry the ground apart. <ref>https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref> <ref>Roeloff, L., et al.   Thermal-contraction polygons on Earth and Mars.
+The initial formation of these polygons begins when sharp drops in temperature cause the permanently frozen ground (permafrost) to contract and fracture. Over time, these individual fractures connect into a vast network of hexagonal or pentagonal shapes. Once these cracks form, they can be filled by windblown sand, ice, or a combination of both, creating "wedges" that physically pry the ground apart. <ref>https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref> <ref>Roeloff, L., et al.   Thermal-contraction polygons on Earth and Mars.</ref>
 A high-centered polygon features a raised central dome and deeply depressed troughs or margins. <ref>Luzzi, E., Heldmann, J. L., Williams, K. E., Nodjoumi, G., Deutsch, A., & Sehlke, A. (2025). Geomorphological evidence of near-surface ice at candidate landing sites in northern Amazonis Planitia, Mars. Journal of Geophysical Research: Planets, 130, e2024JE008724. https://doi.org/10.1029/2024JE008724</ref>  These typically evolve from low-centered polygons through a process of degradation.   If climate conditions change and the ice wedges in the cracks begin to sublimate (turn from solid to gas) or melt, the support for the raised margins is lost.   The edges of the polygon collapse into the widening troughs, leaving the center of the polygon at a higher relative elevation than its crumbling boundaries.  The presence of high-centered polygons often suggests a drying or warming trend where subsurface ice is being depleted.<ref> https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/#:~:text=D%20student%2C%20Laboratoire%20de%20Plan%C3%A9tologie,Mars%20in%20the%20mid%2Dlatitudes.</ref>
@@ Line 642: / Line 642: @@
 2265highcenterpolygonsclose2.jpg|Close-up of high center polygons seen by HiRISE under HiWish program  Note: the black box is the size of a football field.
 </gallery>
 ==Scalloped Terrain==