Common surface features of Mars

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The common surface features of Mars include slope streaks, dust devil tracks, sand dunes, Medusae Fossae Formation, fretted terrain, and Chaos terrain.

Contents

Slope streaks [edit]

When occurring near the top of a dune, dark sand may cascade down the dune leaving dark surface streaks -- streaks that might appear at first to be trees standing in front of the lighter regions.

A new phenomenon known as slope streaks has been uncovered by the HiRISE camera on the Mars Reconnaissance Orbiter. These features appear on crater walls and other slopes, and they are thin and many hundreds of metres long. The streaks have been observed to grow slowly over the course of a year or so, always beginning at a point source. Newly formed streaks are dark in colour but fade as they age until white. The cause is unknown, but theories range from dry dust avalanches (the favoured theory) to brine seepage.[1]
Examples of dark slope streaks from various parts of Mars are shown below. Click on image to get a better view.

Dust devil tracks [edit]

Many areas on Mars experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil travels by, it blows away the coating and exposes the underlying dark surface. These dust devils have been seen both from the ground and from orbit. They have even blown the dust off the solar panels of the two Rovers on Mars, thereby greatly extending their lives.[2] The twin Rovers were designed to last for 3 months; instead, they have lasted six years and are still going. The pattern of the tracks have been shown to change every few months.[3]

Sand dunes [edit]

Many locations on Mars have sand dunes. An erg (or sand sea), made up of aeolian dune fields referred to as the Circumpolar Dune Field[4] surrounds most of the north polar cap.[5] The dunes are covered by a seasonal carbon dioxide frost that forms in early autumn and remains until late spring.[5] Many martian dunes strongly resemble terrestrial dunes but images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter have shown that martian dunes in the north polar region are subject to modification via grainflow triggered by seasonal CO2 sublimation, a process not seen on Earth.[6] Many dunes are black because they are derived from the dark volcanic rock basalt. Extraterrestrial sand seas such as those found on Mars are referred to as "undae" from the Latin for waves.

  • Dark dunes (probably basalt) which form a dark spot in Noachis. Picture from Mars Global Surveyor.

  • Wide view of dunes in Noachis, as seen by HiRISE.

  • Close-up View of dunes in previous image, as seen by HiRISE. Note how sand barely covers some boulders.

  • Rabe Crater Floor, as seen by HiRISE. Click on image to see layers. Dark sand that made the dunes was probably blown in from elsewhere.

  • Barchan sand dunes in the Hellespontus region, as seen by HiRISE. The horns point in the downwind direction.

  • Proctor Crater Ripples and Dunes, as seen by HiRISE.

Medusae Fossae Formation [edit]

The Medusae Fossae Formation is a soft, easily eroded deposit that extends for nearly 1,000 km along the equator of Mars. Sometimes the formation appears as a smooth and gently undulating surface; however, in places it is wind-sculpted into ridges and grooves.[7] Radar imaging has suggested that the region may contain either extremely porous rock (for example volcanic ash) or deep layers of glacier-like ice deposits amounting to about the same quantity as is stored in Mars' south polar cap.[8][9]

The lower portion (member) of Medusae Fossae Formation contains many patterns and shapes that are thought to be the remains of streams. It is believed that streams formed valleys that were filled and became resistant to erosion by cementaion of minerals or by the gathering of a coarse covering layer. These inverted stream beds are sometimes called sinuous ridges or raised curvilinear features. They may be a kilometer or so in length. Their height ranges from a meter to greater than 10 meters, while the width of the narrow ones is less than 10 meters.[10]

The wind has eroded the surface of the formation into a series of linear ridges called yardangs. These ridges generally point in the direction of the prevailing winds that carved them and demonstrate the erosive power of martian winds. The easily eroded nature of the Medusae Fossae Formation suggests that it is composed of weakly cemented particles, and was most likely formed by the deposition of wind-blown dust or volcanic ash. Layers are seen in parts of the formation. A resistant caprock on the top of yardangs has been observed in Viking,[11] Mars Global Surveyor,[12] and HiRISE photos.[13] Very few impact craters are visible throughout the area so the surface is relatively young.[14]

  • Medusae Fossae Formation as seen with Mars Odyssey's THEMIS. Notice elongated formations called yardangs.

  • Medusae Fossae Formation as seen with HiRISE. Image is located in the Aeolis quadrangle.

  • Yardangs in Medusae Fossae Formation with caprock labeled, as seen by HiRISE. Location is Aeolis quadrangle.

  • Layers in lower member of Medusae Fossae Formation, as seen by HiRISE. Location is Aeolis quadrangle.

Fretted terrain [edit]

Fretted terrain is a type of surface feature common to certain areas of Mars and discovered in Mariner 9 images. It lies between two different surfaces. The surface of Mars can be divided into two parts: low, young, uncratered plains that cover most of the northern hemisphere, and high-standing, old, heavily cratered areas that cover the southern hemisphere and a small part of the northern hemisphere. Between these two zones is the fretted terrain, containing a complicated mix of cliffs, mesas, buttes, and straight-walled and sinuous canyons. Fretted terrain contains smooth, flat lowlands along with steep cliffs. The scarps or cliffs are usually 1 to 2 km high. Channels in the area have wide, flat floors and steep walls.[15] Fretted terrain is most common in northern Arabia, between latitudes 30°N and 50°N and longitudes 270°W and 360°W.[16] Parts of the fretted terrain are called Deuteronilus Mensae and Protonilus Mensae.

In fretted terrain, the land seems to transition from narrow straight valleys to isolated mesas. Most of the mesas are surrounded by forms that have been called a variety of names (circum-mesa aprons, debris aprons, rock glaciers, and Lobate Debris Aprons).[17] At first they appeared to resemble rock glaciers on Earth, but scientists could not be sure. Eventually, proof of their true nature was discovered by radar studies with the Mars Reconnaissance Orbiter and showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.[18][19][20][21][22][23]

Besides rock covered glaciers around mesas, the region has many steep-walled valleys with lineations—ridges and grooves—on their floors. The material comprising these valley floors is called lineated valley fill. In some of the best images taken by the Viking Orbiters, some of the valley fill appeared to resemble alpine glaciers on Earth. Given this similarity, some scientists assumed that the lineations on these valley floors might have formed by flow of ice in (and perhaps through) these canyons and valleys. Today, it is generally agreed that glacial flow caused the lineations.

  • Fretted terrain of Ismenius Lacus showing flat floored valleys and cliffs. Photo taken with Mars Orbiter Camera (MOC)on the Mars Global Surveyor.

  • Enlargement of the photo on the left showing cliff. Photo taken with high resolution camera of Mars Global Surveyor (MGS).

  • Lobate Debris Apron in Phlegra Montes, as seen by HiRISE. The debris apron is probably mostly ice with a thin covering of rock debris, so it could be a source of water for future Martian colonists. Image from the Cebrenia quadrangle. Scale bar is 500 meters long.

  • Reull Vallis with lineated floor deposits, as seen by THEMIS. Image located in Hellas quadrangle. Click on image to see relationship to other features.

  • Fretted Terrain near Reull Vallis, as seen by HiRISE.

  • Close-up of Fretted Terrain near Reull Vallis, as seen by HiRISE. This area would be a challenge to walk across.

Chaos terrain [edit]

Chaos terrain is believed to be associated with the release of huge amounts of water. The chaotic features may have collapsed when water came out of the surface. Martian outflow channels commonly begin with a Chaos region. A chaotic region can be recognized by a tangle of mesas, buttes, and hills, all chopped through with valleys which in places look almost patterned. Some parts of this chaotic area have not collapsed completely—they are still formed into large mesas, so they may still contain water ice.[24] Chaotic terrain occurs in numerous locations on Mars, and always gives the strong impression that something abruptly disturbed the ground. Chaos regions formed long ago. By counting craters (more craters in any given area means an older surface) and by studying the valleys' relations with other geological features, scientists have concluded the channels formed 2.0 to 3.8 billion years ago.[25]

  • THEMIS image of wide view of following HiRISE images. Black box shows approximate location of HiRISE images. This image is just a part of the vast area known as Aureum Chaos. Click on image to see more details.

  • Aureum Chaos, as seen by HiRISE, under the HiWish program.

  • Close up view of previous image, as seen by HiRISE under HiWish program. Small round dots are boulders.

Scalloped topography [edit]

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[26][27] in the northern hemisphere and in the region of Peneus and Amphitrites Patera[28][29] 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.[30]

References [edit]

  1. ^ "Newly-Formed Slope Streaks". NASA. Retrieved 2007-03-16. 
  2. ^ "Mars Exploration Rover Mission: Press Release Images: Spirit". Marsrovers.jpl.nasa.gov. Retrieved 2012-01-16. 
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  5. ^ a b Schatz, Volker; H. Tsoar, K. S. Edgett, E. J. R. Parteli, H. J. Herrmann (2006). "Evidence for indurated sand dunes in the Martian north polar region". Journal of Geophysical Research 111 (E04006). Bibcode:2006JGRE..11104006S. doi:10.1029/2005JE002514. 
  6. ^ Hansen, C. J.; M. Bourke, N. T. Bridges, S. Byrne, C. Colon, S. Diniega, C. Dundas, K. Herkenhoff, A. McEwen, M. Mellon, G. Portyankina, N. Thomas (4 February 2011). "Seasonal Erosion and Restoration of Mars’ Northern Polar Dunes". Science 331 (6017): 575–578. Bibcode:2011Sci...331..575H. doi:10.1126/science.1197636. 
  7. ^ Fraser Cain (2005-03-29). "Medusa Fossae Region on Mars". Universetoday.com. Retrieved 2012-01-16. 
  8. ^ Shiga, David (1 November 2007). "Vast amount of water ice may lie on Martian equator". New Scientist Space. Retrieved 20 January 2011. 
  9. ^ Watters, T. R.; Campbell, B.; Carter, L.; Leuschen, C. J.; Plaut, J. J.; Picardi, G.; Orosei, R.; Safaeinili, A. et al. (2007). "Radar Sounding of the Medusae Fossae Formation Mars: Equatorial Ice or Dry, Low-Density Deposits?". Science 318 (5853): 1125–8. Bibcode:2007Sci...318.1125W. doi:10.1126/science.1148112. PMID 17975034. 
  10. ^ Zimbelman, James R.; Griffin, Lora J. (2010). "HiRISE images of yardangs and sinuous ridges in the lower member of the Medusae Fossae Formation, Mars". Icarus 205 (1): 198–210. Bibcode:2010Icar..205..198Z. doi:10.1016/j.icarus.2009.04.003. 
  11. ^ Scott, David H.; Tanaka, Kenneth L. (1982). "Ignimbrites of Amazonis Planitia Region of Mars". Journal of Geophysical Research 87 (B2): 1179–1190. Bibcode:1982JGR....87.1179S. doi:10.1029/JB087iB02p01179. 
  12. ^ Malin, MC; Carr, MH; Danielson, GE; Davies, ME; Hartmann, WK; Ingersoll, AP; James, PB; Masursky, H et al. (March 1998). "Early views of the martian surface from the Mars Orbiter Camera of Mars Global Surveyor". Science 279 (5357): 1681–5. Bibcode:1998Sci...279.1681M. doi:10.1126/science.279.5357.1681. PMID 9497280. 
  13. ^ Mandt, Kathleen E.; De Silva, Shanaka L.; Zimbelman, James R.; Crown, David A. (2008). "The origin of the Medusae Fossae Formation, Mars: Insights from a synoptic approach". Journal of Geophysical Research 113 (E12). Bibcode:2008JGRE..11312011M. doi:10.1029/2008JE003076. 
  14. ^ http://themis.asu.edu/zoom-20020416a
  15. ^ Strom, R.G.; Croft, S.K.; Barlow, N.G. (1992). "The Martian Impact Cratering Record". In Kieffer, H.H.; Jakosky, B.M.; Snyder, C.W. et al. Mars. Tucson: University of Arizona Press. pp. 384–385. ISBN 978-0-8165-1257-7. 
  16. ^ "Catalog Page for PIA01502". Photojournal.jpl.nasa.gov. Retrieved 2012-01-16. 
  17. ^ http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1053.pdf
  18. ^ Head, J. et al. (2005). "Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars". Nature 434 (7031): 346–50. Bibcode:2005Natur.434..346H. doi:10.1038/nature03359. PMID 15772652. 
  19. ^ Plaut, J. et al. (2008). "Radar Evidence for Ice in Lobate Debris Aprons in the Mid-Northern Latitudes of Mars". Lunar and Planetary Science. XXXIX: 2290. 
  20. ^ Holt, J. et al. (2008). "Radar Sounding Evidence for Ice within Lobate Debris Aprons near Hellas Basin, Mid-Southern Latitudes of Mars". Lunar and Planetary Science. XXXIX: 2441. 
  21. ^ Plaut Jeffrey J. et al. (28 January 2009). "Radar evidence for ice in lobate debris aprons in the mid-northern latitudes of Mars". Geophysical Research Letters 36 (2): L02203. Bibcode:2009GeoRL..3602203P. doi:10.1029/2008GL036379. 
  22. ^ "Mars' climate in flux: Mid-latitude glaciers | Mars Today - Your Daily Source of Mars News". Mars Today. Retrieved 2012-01-16. 
  23. ^ http://news.brown.edu/pressreleases/2008/04/martian-glaciers
  24. ^ "Unraveling the Chaos of Aram | Mars Odyssey Mission THEMIS". Themis.asu.edu. Retrieved 2012-01-16. 
  25. ^ [2][dead link]
  26. ^ Lefort, A.; Russell, P. S.; Thomas, N.; McEwen, A. S.; Dundas, C. M.; Kirk, R. L. (2009). "Observations of periglacial landforms in Utopia Planitia with the High Resolution Imaging Science Experiment (HiRISE)". Journal of Geophysical Research 114 (E4). Bibcode:2009JGRE..11404005L. doi:10.1029/2008JE003264. 
  27. ^ Morgenstern, A; Hauber, E; Reiss, D; van Gasselt, S; Grosse, G; Schirrmeister, L (2007). "Deposition and degradation of a volatile-rich layer in Utopia Planitia, and implications for climate history on Mars" (PDF). Journal of Geophysical Research - Planets 112 (E6): E06010. Bibcode:2007JGRE..11206010M. doi:10.1029/2006JE002869. 
  28. ^ Lefort, A.; Russell, P.S.; Thomas, N. (2010). "Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE". Icarus 205 (1): 259. Bibcode:2010Icar..205..259L. doi:10.1016/j.icarus.2009.06.005. 
  29. ^ Zanetti, M.; Hiesinger, H.; Reiss, D.; Hauber, E.; Neukum, G. (2009). "Scalloped Depression Development on Malea Planum and the Southern Wall of the Hellas Basin, Mars". Lunar and Planetary Science 40. abstract 2178. Bibcode:2009LPI....40.2178Z. 
  30. ^ http://hiroc.lpl.arizona.edu/images/PSP?diafotizo.php?ID=PSP_002296_1215
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