Memnonia quadrangle - Revision history

Suitupshowup at 20:38, 22 January 2025

2025-01-22T20:38:45Z

Suitupshowup at 15:20, 13 December 2024

2024-12-13T15:20:29Z

Suitupshowup: added image

2024-12-13T15:19:02Z

added image

Suitupshowup: /* Lava flows */

2023-12-23T22:23:17Z

Lava flows

Suitupshowup: /* Valles */

2023-12-23T22:21:39Z

Valles

Michel Lamontagne at 12:59, 19 August 2021

2021-08-19T12:59:35Z

Michel Lamontagne: /* See also */

2021-08-19T12:57:53Z

Suitupandshowup: /* Layers */ added ref

2021-08-02T22:45:00Z

Layers: added ref

Michel Lamontagne at 19:35, 14 December 2020

2020-12-14T19:35:52Z

Show changes

Suitupandshowup at 20:14, 25 March 2020

2020-03-25T20:14:30Z

← Older revision		Revision as of 20:38, 22 January 2025
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	The Memnonia quadrangle contains some nice ancient river valleys including a large river system called Mangala Vallis. There are also wind-eroded deposits and lava flows from the large volcanic region called Tharsis.		The Memnonia quadrangle contains some nice ancient river valleys including a large river system called Mangala Vallis. There are also wind-eroded deposits and lava flows from the large volcanic region called Tharsis.
		+
		+	In this article, some of the best pictures from a number of spacecraft will show what the landscape looks like in this quadrangle. The origins and significance of all features will be explained as they are currently understood.
		+

	The Memnonia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) and is also referred to as MC-16 (Mars Chart-16).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>		The Memnonia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) and is also referred to as MC-16 (Mars Chart-16).<ref>Davies, M.E.; Batson, R.M.; Wu, S.S.C. "Geodesy and Cartography" in Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W.; Matthews, M.S., Eds. ''Mars.'' University of Arizona Press: Tucson, 1992.</ref>

← Older revision		Revision as of 15:20, 13 December 2024
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	[[File:Collage memnonia.jpg\|Features of Features of Memnonia quadrangle, as seen by HiRISE under under HiWish program\|600pxr\| Features of Memnonia quadrangle]]		[[File:Collage memnonia.jpg\|Features of Features of Memnonia quadrangle, as seen by HiRISE under under HiWish program\|600pxr\| Features of Memnonia quadrangle]]

−	Scenes of the Memnonia ~~quadrangle~~ quadrangle	+	Scenes of the Memnonia quadrangle

← Older revision		Revision as of 15:19, 13 December 2024
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	Geological map of the Memnonia quadrangle, USGS: https://pubs.usgs.gov/imap/1137/plate-1.pdf		Geological map of the Memnonia quadrangle, USGS: https://pubs.usgs.gov/imap/1137/plate-1.pdf
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		+	[[File:Collage memnonia.jpg\|Features of Features of Memnonia quadrangle, as seen by HiRISE under under HiWish program\|600pxr\| Features of Memnonia quadrangle]]
		+
		+	Scenes of the Memnonia quadrangle quadrangle
		+

	The Memnonia quadrangle contains some nice ancient river valleys including a large river system called Mangala Vallis. There are also wind-eroded deposits and lava flows from the large volcanic region called Tharsis.		The Memnonia quadrangle contains some nice ancient river valleys including a large river system called Mangala Vallis. There are also wind-eroded deposits and lava flows from the large volcanic region called Tharsis.

@@ Line 195: / Line 195: @@
 [[File:ESP 034833 1595memnonialava.jpg|600pxr|Lava flow.  Lava flow stopped when it encountered the higher ground of a mound.  Picture was taken with HiRISE under HiWish program.]]
-                                       Lava flow.  Lava flow stopped when it encountered the higher ground of a mound.
+                Lava flow.  Lava flow stopped when it encountered the higher ground of a mound.
 ==Fifty Years of Mars Imaging: from Mariner 4 to HiRISE==

← Older revision		Revision as of 22:21, 23 December 2023
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	[[File:ESP 047467 1685channalridge.jpg\|600pxr\|Channel that has eroded through a wrinkle ridge, as seen by HiRISE under HiWish program. Arrow shows point where channel eroded through ridge.]]		[[File:ESP 047467 1685channalridge.jpg\|600pxr\|Channel that has eroded through a wrinkle ridge, as seen by HiRISE under HiWish program. Arrow shows point where channel eroded through ridge.]]

−	Channel that has eroded through a wrinkle ridge Arrow shows point where channel eroded through ridge.	+	Channel that has eroded through a wrinkle ridge Arrow shows point where channel eroded through ridge.

← Older revision		Revision as of 12:59, 19 August 2021
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	Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/ \|title=Stones, Wind, and Ice: A Guide to Martian Impact Craters \|publisher=Lpi.usra.edu \|date= \|</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer\|title=Mars\|url=https://books.google.com/books\|date=1992\|publisher=University of Arizona Press\|</ref> Sometimes craters will display layers; those layers show us what kinds of rocks were present in the past. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, rocks around the crater are samples of what lies deep under the surface. At times, bright rays surround craters because the impact has gone down to a bright layer of rocks, and then placed bright rocks on the darker surface. An image above from Mars Global Surveyor shows this.		Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits. As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/ \|title=Stones, Wind, and Ice: A Guide to Martian Impact Craters \|publisher=Lpi.usra.edu \|date= \|</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer\|title=Mars\|url=https://books.google.com/books\|date=1992\|publisher=University of Arizona Press\|</ref> Sometimes craters will display layers; those layers show us what kinds of rocks were present in the past. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, rocks around the crater are samples of what lies deep under the surface. At times, bright rays surround craters because the impact has gone down to a bright layer of rocks, and then placed bright rocks on the darker surface. An image above from Mars Global Surveyor shows this.
		+
		+	[[Columbus Crater]] shows signs of mineral deposits

	<gallery class="center" widths="380px" heights="360px">		<gallery class="center" widths="380px" heights="360px">

@@ Line 75: / Line 75: @@
 Many places on Mars show rocks arranged in layers.  Layers are also called strata. Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |</ref> Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments. Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.<ref>https://iopscience.iop.org/article/10.3847/PSJ/abe773/pdf</ref>
-Recent research with an orbiting near-infrared spectrometer (which reveals the types of minerals present based on the wavelengths of light they absorb) found evidence of layers of both clay and sulfates in Columbus crater.<ref> B. Boatwright and J. Head.  2021.   A Noachian Proglacial Paleolake on Mars: Fluvial Activity and Lake Formation within a Closed-source Drainage Basin Crater and Implications for Early Mars Climate.  The Planetary Science Journal, 2:52 (9pp).</ref>
+Recent research with an orbiting near-infrared spectrometer (which reveals the types of minerals present based on the wavelengths of light they absorb) found evidence of layers of both clay and sulfates in Columbus crater.<ref>B. Boatwright and J. Head.  2021.   A Noachian Proglacial Paleolake on Mars: Fluvial Activity and Lake Formation within a Closed-source Drainage Basin Crater and Implications for Early Mars Climate.  The Planetary Science Journal, 2:52 (9pp).</ref>
 <ref>Cabrol, N. and E. Grin (eds.).  2010.  Lakes on Mars.  Elsevier.NY.</ref>  This is exactly what would appear if a large lake had slowly evaporated.<ref>Wray, J. et al.  2009.  Columbus Crater and other possible plaelakes in Terra Sirenum, Mars.  Lunar and Planetary Science Conference.  40: 1896.</ref>   Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater.<ref>http://news.nationalgeographic.com/news/2009/11/091125-mars-crater-lake-michigan-water_2.html |title=Martian "Lake Michigan" Filled Crater, Minerals Hint |publisher=News.nationalgeographic.com |</ref>
 Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.<ref>http://themis.asu.edu/features/nilosyrtis |title=Target Zone: Nilosyrtis? &#124; Mars Odyssey Mission THEMIS |publisher=Themis.asu.edu |</ref>  Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.<ref>http://hirise.lpl.arizona.edu/PSP_004046_2080 |title=HiRISE &#124; Craters and Valleys in the Elysium Fossae (PSP_004046_2080) |publisher=Hirise.lpl.arizona.edu |date= |</ref>
@@ Line 234: / Line 234: @@
 *[[Mars Global Surveyor]]
 *[[Rivers on Mars]]

@@ Line 74: / Line 74: @@
 ==Layers==
-Many places on Mars show rocks arranged in layers.  Layers are also called strata. Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |</ref> Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments. Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.  Recent research with an orbiting near-infrared spectrometer (which reveals the types of minerals present based on the wavelengths of light they absorb) found evidence of layers of both clay and sulfates in Columbus crater.<ref>Cabrol, N. and E. Grin (eds.).  2010.  Lakes on Mars.  Elsevier.NY.</ref>  This is exactly what would appear if a large lake had slowly evaporated.<ref>Wray, J. et al.  2009.  Columbus Crater and other possible plaelakes in Terra Sirenum, Mars.  Lunar and Planetary Science Conference.  40: 1896.</ref>   Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater.<ref>http://news.nationalgeographic.com/news/2009/11/091125-mars-crater-lake-michigan-water_2.html |title=Martian "Lake Michigan" Filled Crater, Minerals Hint |publisher=News.nationalgeographic.com |</ref>
+Many places on Mars show rocks arranged in layers.  Layers are also called strata. Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.<ref>http://hirise.lpl.arizona.edu?PSP_008437_1750 |title=HiRISE &#124; High Resolution Imaging Science Experiment |publisher=Hirise.lpl.arizona.edu?psp_008437_1750 |</ref> Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments. Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.<ref>https://iopscience.iop.org/article/10.3847/PSJ/abe773/pdf</ref>
 Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.<ref>http://themis.asu.edu/features/nilosyrtis |title=Target Zone: Nilosyrtis? &#124; Mars Odyssey Mission THEMIS |publisher=Themis.asu.edu |</ref>  Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.<ref>http://hirise.lpl.arizona.edu/PSP_004046_2080 |title=HiRISE &#124; Craters and Valleys in the Elysium Fossae (PSP_004046_2080) |publisher=Hirise.lpl.arizona.edu |date= |</ref>

@@ Line 101: / Line 101: @@
-Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits.  As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/ |title=Stones, Wind, and Ice: A Guide to Martian Impact Craters |publisher=Lpi.usra.edu |date= |</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer|title=Mars|url=https://books.google.com/books|date=1992|publisher=University of Arizona Press|</ref>  Sometimes craters will display layers; those layers show us what kinds of rocks were present in the past.  Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface.  Hence, rocks around the crater are samples of  what lies deep under the surface.  At times, bright rays surround craters because the impact has gone down to a bright layer of rocks, and then tossed out the bright rocks on the darker surface.  An image below from Mars Global Surveyor shows this.
+Impact craters generally have a rim with ejecta around them, in contrast volcanic craters usually do not have a rim or ejecta deposits.  As craters get larger (greater than 10 km in diameter) they usually have a central peak.<ref>http://www.lpi.usra.edu/publications/slidesets/stones/ |title=Stones, Wind, and Ice: A Guide to Martian Impact Craters |publisher=Lpi.usra.edu |date= |</ref> The peak is caused by a rebound of the crater floor following the impact.<ref>Hugh H. Kieffer|title=Mars|url=https://books.google.com/books|date=1992|publisher=University of Arizona Press|</ref>  Sometimes craters will display layers; those layers show us what kinds of rocks were present in the past.  Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface.  Hence, rocks around the crater are samples of  what lies deep under the surface.  At times, bright rays surround craters because the impact has gone down to a bright layer of rocks, and then placed bright rocks on the darker surface.  An image above from Mars Global Surveyor shows this.
 <gallery class="center"  widths="380px" heights="360px">
@@ Line 112: / Line 112: @@
 ESP 035163 1560memnoniafractures.jpg|Troughs on the floor of Bernard Crater showing many boulders
-ESP 034596 1565memnoniafractures.jpg|Troughs on the floor of Bernard Crater
+ESP 034596 1565memnoniafractures.jpg|More examples of troughs on the floor of Bernard Crater
-Image:27001layersclose.jpg|Close-up of layers in a pit on crater floor, as seen by HiRISE under HiWish program.
+Image:27001layersclose.jpg|Close-up of layers in a pit on crater floor  The box shows the size of a football field.
 Wikiburton.jpg|Middle section of Burton Crater, showing central mound, as seen by CTX camera (on Mars Reconnaissance Orbiter).
@@ Line 125: / Line 125: @@
 ==Ridges==
-Ridges on Mars may be due to different causes.  Long straight ridges are thought to be dikes.  Curved and branched ridges may be examples of inverted topography, and groups of straight ridges that cross each other may be the result of impacts.  These intersecting box-like ridges are called linear ridge networks.
+Ridges on Mars may be due to different causes.  Long straight ridges are thought to be dikes (from magma movements).  Curved and branched ridges may be examples of inverted topography, and groups of straight ridges that cross each other may be the result of impacts.  These intersecting box-like ridges are called linear ridge networks.
 Linear ridge networks are found in various places on Mars in and around craters.<ref>Head, J., J. Mustard.  2006.  Breccia dikes and crater-related faults in impact craters on Mars: Erosion and exposure on the floor of a crater 75 km in diameter at the dichotomy boundary, Meteorit. Planet Science: 41, 1675-1690.</ref>   Ridges often appear as mostly straight segments that intersect in a lattice-like manner.  They are hundreds of meters long, tens of meters high, and several meters wide.  Even though the exact origin is not known at present, one popular idea is that impacts created fractures in the surface, these fractures later acted as channels for fluids.  Fluids carried minerals which hardened into the ridges we see today.  With the passage of time, surrounding material was eroded away, thereby leaving hard ridges behind.
@@ Line 146: / Line 146: @@
 1725yardangs2.jpg|Close view of yardangs in previous image
 1725yardangsclose.jpg|Close view of yardangs from a previous image, as seen by HiRISE under HiWish program
-Image:27001yardangs.jpg|Close up of crater floor showing yardangs and dark slope streaks, as seen by HiRISE under HiWish program
+Image:27001yardangs.jpg|Close up of crater floor showing yardangs and dark slope streaks
 1750yardangs.jpg|Yardangs
@@ Line 156: / Line 156: @@
 == Dark slope streaks ==
-Many places on Mars show dark slope streaks on steep slopes, like crater walls.  The youngest streaks are the darkest<ref>Schorghofer, N, et al.  2007.  Three decades of slope streak activity on Mars.  Icarus.  191:132-140.</ref>  Often they begin as a small narrow spot then widen and extend downhill for hundreds of meters.   It is most generally accepted that the streaks represent avalanches of dust.<ref>Ferris, J. C.; Dohm, J.M.; Baker, V.R.; Maddock III, T. (2002). Dark Slope Streaks on Mars: Are Aqueous Processes Involved? ''Geophys. Res. Lett.,'' '''29'''(10), 1490, </ref>     When a thin layer of dust is removed, the underlying surface is dark.  Much of the Martian surface is covered with dust.  Dust storms are frequent, especially when the spring season begins in the southern hemisphere.  At that time, Mars is 40% closer to the sun.  The orbit of Mars is much more elliptical then the Earth's.  That is the difference between the farthest point from the sun and the closest point to the sun is very great for Mars, but very little for the Earth.  Also, every few years, the entire planet is engulfed in a global dust storm.  When NASA's [[Mariner 9]] craft arrived there, nothing could be seen through the dust storm.<ref>Kieffer.  1992.  ISBN|0-517-00192-6</ref> Other global dust storms have also been observed, since that time.  Dark streaks can be seen in the image below taken with HiRISE of the central mound in Nicholson Crater.  At least one streak in the image splits into two when encountering an obstacle.
+Many places on Mars show dark slope streaks on steep slopes, like crater walls.  The youngest streaks are the darkest<ref>Schorghofer, N, et al.  2007.  Three decades of slope streak activity on Mars.  Icarus.  191:132-140.</ref>  Often they begin as a small narrow spot then widen and extend downhill for hundreds of meters.   It is most generally accepted that the streaks represent avalanches of dust.<ref>Ferris, J. C.; Dohm, J.M.; Baker, V.R.; Maddock III, T. (2002). Dark Slope Streaks on Mars: Are Aqueous Processes Involved? ''Geophys. Res. Lett.,'' '''29'''(10), 1490, </ref>     When a thin layer of dust is removed, the dark underlying surface becomes visible.  Much of the Martian surface is covered with dust with much of it resulting from dust storms.  Dust storms are frequent, especially when the spring season begins in the southern hemisphere.  At that time, Mars is 40% closer to the sun.  The orbit of Mars is much more elliptical then the Earth's.  That is the difference between the farthest point from the sun and the closest point to the sun is very great for Mars, but very little for the Earth.  Also, every few years, the entire planet is engulfed in a global dust storm.  When NASA's [[Mariner 9]] craft arrived there, nothing could be seen through the dust storm.<ref>Kieffer.  1992.  ISBN|0-517-00192-6</ref> Other global dust storms have also been observed, since that time.  Dark streaks can be seen in the image below taken with HiRISE of the central mound in Nicholson Crater.  At least one streak in the image splits into two when encountering an obstacle.
-Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, the team of scientists   discovered patterns in the data.  The number of streaks was greatest closer to the impact site.  So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site.  The curved wings resembled curved knives, called scimitars.  This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark streaks.  At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars. Icarus, 2012; 217 (1): 194 {{doi|10.1016/j.icarus.2011.10.026}}</ref> <ref>http://redplanet.asu.edu/ |title=Red Planet Report &#124; What's up with Mars |publisher=Redplanet.asu.edu |date= |</ref>
+Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, the team of scientists   discovered patterns in the data.  The number of streaks was greatest closer to the impact site.  So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site.  The curved wings resembled curved knives, called scimitars.  This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark streaks.  At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes.<ref>Kaylan J. Burleigh, Henry J. Melosh, Livio L. Tornabene, Boris Ivanov, Alfred S. McEwen, Ingrid J. Daubar. Impact air blast triggers dust avalanches on Mars. Icarus, 2012; 217 (1): 194 10.1016/j.icarus.2011.10.026</ref> <ref>http://redplanet.asu.edu/ |title=Red Planet Report &#124; What's up with Mars |publisher=Redplanet.asu.edu |date= |</ref>
 <gallery class="center"  widths="380px" heights="360px">
@@ Line 170: / Line 170: @@
 ==Fossa on Mars==
-Large troughs (long narrow depressions) are called fossae in the geographical language used for Mars.  This term is derived from Latin; therefore fossa is singular and fossae is plural.<ref>http://www.marsartgallery.com/marsnames.html |title=Mars Art Gallery Martian Feature Name Nomenclature |publisher=Marsartgallery.com |date= |</ref> Troughs form when the crust is stretched until it breaks.  The stretching can be due to the large weight of a nearby volcano.  A trough often has two breaks with a middle section lower, leaving steep cliffs along the sides; such a trough is called a graben.<ref>http://hirise.lpl.arizona.edu/PSP_008641_2105 |title=HiRISE &#124; Craters and Pit Crater Chains in Chryse Planitia (PSP_008641_2105) |publisher=Hirise.lpl.arizona.edu |date= |</ref> Lake George, in northern New York State, is a lake that sits in a graben.
+Large troughs (long narrow depressions) are called fossae in the geographical language used for Mars.  This term is derived from Latin; therefore fossa is singular and fossae is plural.<ref>http://www.marsartgallery.com/marsnames.html |title=Mars Art Gallery Martian Feature Name Nomenclature |publisher=Marsartgallery.com |date= |</ref> Troughs form when the crust is stretched until it breaks.  The stretching can be due to the great weight of a nearby volcano.  A trough often has two breaks with a middle section lower, leaving steep cliffs along the sides; such a trough is called a graben.<ref>http://hirise.lpl.arizona.edu/PSP_008641_2105 |title=HiRISE &#124; Craters and Pit Crater Chains in Chryse Planitia (PSP_008641_2105) |publisher=Hirise.lpl.arizona.edu |date= |</ref> Lake George, in northern New York State, is a lake that occupies a graben.
 Other ideas have been suggested for the formation of fossae.  There is evidence that they are associated with dikes of magma.  Magma might move along, under the surface, breaking the rock and more importantly melting ice.  The resulting action would cause a crack to form at the surface.  Dikes caused both by tectonic stretching (extension) and by dikes are found in Iceland.<ref>http://hirise.lpl.arizona.edu/PSP_005376_1575 |title=HiRISE &#124; Graben in Memnonia Fossae (PSP_005376_1575) |publisher=Hirise.lpl.arizona.edu |date= |</ref>  An example of a graben caused by a dike is shown below in the image Memnonia Fossae, as seen by HiRISE.
@@ Line 179: / Line 179: @@
 Image:Graben in Memnonia Fossae.JPG|Graben in Memnonia Fossae, as seen by HiRISE.  This graben is believed to be the result of magmatic dikes rather than regional tectonic stretching.  The scale bar is 1000 meters long.
-Image:26987fossaepits.jpg|Large pits in Sirenum Fossae, as seen by HiRISE under HiWish program
+Image:26987fossaepits.jpg|Large pits in Sirenum Fossae  Pits sometimes signal the start of a graben.
 ESP 049854 1535troughcrater.jpg|Trough cutting through an impact crater,
@@ Line 199: / Line 199: @@
 [[File:52438cameramaparrow.jpg|600pxr|Map showing area covered in the above photos with a black rectangle. Blue arrow indicates the spot eventually imaged by HiRISE. The relative positions of Columbus Crater, Williams Crater, Ejriksson Crater, Dejnev Crater, and Bernard Crater are shown.]]
-Map showing area covered in the above photos with a black rectangle. Blue arrow indicates the spot eventually imaged by HiRISE. The relative positions of Columbus Crater, Williams Crater, Ejriksson Crater, Dejnev Crater, and Bernard Crater are shown.
+Area in black rectangle is covered in the photos below. Blue arrow indicates the spot eventually imaged by HiRISE. The relative positions of Columbus Crater, Williams Crater, Ejriksson Crater, Dejnev Crater, and Bernard Crater are shown.
@@ Line 211: / Line 211: @@
 Composite demonstrating relative resolution of 7 different cameras that imaged Mars: HiRISE (Mars Reconnaissance Orbiter), THEMIS VIS (Mars Odyssey), MOC-WAC (Mars Global Surveyor), HRSC (Mars Express), CTX (Mars Reconnaissance Orbiter),  Viking, Mariner 4.  Location is Memnonia quadrangle. Blue arrow on some pictures points to same location with different cameras. Red box with CTX image shows location of the next frame from HiRISE.
 ==More features of Memnonia quadrangle==