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Ismenius Lacus quadrangle

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Ismenius Lacus quadrangle

Ismenius Lacus quadrangle
Map of Ismenius Lacus quadrangle from Mars Orbiter Laser Altimeter (MOLA) data. The highest elevations are red and the lowest are blue.
Coordinates
Image of the Ismenius Lacus Quadrangle (MC-5). The northern area contains relatively smooth plains; the central area, mesas and buttes; and, the southern area, numerous craters.

The Ismenius Lacus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars’ eastern hemisphere and covers 0° to 60° east longitude (300° to 360° west longitude) and 30° to 65° north latitude. The quadrangle uses a Lambert conformal conic projection at a nominal scale of 1:5,000,000 (1:5M). The Ismenius Lacus quadrangle is also referred to as MC-5 (Mars Chart-5).[1] The southern and northern borders of the Ismenius Lacus quadrangle are approximately 3,065 km (1,905 mi) and 1,500 km (930 mi) wide, respectively. The north to south distance is about 2,050 km (1,270 mi) (slightly less than the length of Greenland).[2] The quadrangle covers an approximate area of 4.9 million square km, or a little over 3% of Mars’ surface area.[3]

The Ismenius Lacus quadrangle contains Deuteronilus Mensae and Protonilus Mensae, two places that are of special interest to scientists. They contain evidence of present and past glacial activity. They also have a landscape unique to Mars, called Fretted terrain. The largest crater in the area is Lyot Crater which contains channels probably carved by liquid water.[4] [5]

Origin of Name

Ismenius Lacus is the name of a telescopic albedo feature located at 40° N and 30° E on Mars. The term is Latin for Ismenian Lake. Ismenia is the poetic name for Thebes, a city in Greece. The name was approved by the International Astronomical Union (IAU) in 1958.[6]

Physiography and Geology

In eastern Ismenius Lacus, lies Mamers Valles, a giant outflow channel.

Lyot Crater

The northern plains are generally flat and smooth with few craters. However, a few large craters do stand out. The giant impact crater, Lyot, is easy to see in the northern part of Ismenius Lacus.[7] Lyot Crater is the deepest point in Mars's northern hemisphere.[8] One image below of Lyot Crater Dunes shows a variety of interesting forms: dark dunes, light-toned deposits, and Dust Devil Tracks. Dust devils, which resemble miniature tornados create the tracks by removing a thin, but bright deposit of dust to reveal the darker underlying surface. Light-toned deposits are widely believed to contain minerals formed in water. Research, published in June 2010, described evidence for liquid water in Lyot crater in the past.[4] [5]

Other Craters

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.[9] The peak is caused by a rebound of the crater floor following the impact.[10] Sometimes craters will display layers in their walls. Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface. Hence, craters are useful for showing us what lies deep under the surface.

Fretted Terrain

The Ismenius Lacus quadrangle contains several interesting features such as Fretted terrain, parts of which are found in Deuteronilus Mensae and Protonilus Mensae. 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. Many buttes and mesas are present.[11] In fretted terrain the land seems to transition from narrow straight valleys to isolated mesas.[12] 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.[13] At first they appeared to resemble rock glaciers on Earth. But scientists could not be sure. Even after the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) took a variety of pictures of fretted terrain, experts could not tell for sure if material was moving or flowing as it would in an ice-rich deposit (glacier). Eventually, proof of their true nature was discovered by radar studies with the Mars Reconnaissance Orbiter showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.[14][15]

Glaciers

Glaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes, especially the Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice.[10][14][16] In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.[17] The ice was probably deposited as snowfall during an earlier climate when the poles were tilted more.[18] It would be difficult to take a hike on the fretted terrain where glaciers are common because the surface is folded, pitted, and often covered with linear striations.[19] The striations show the direction of movement. Much of this rough texture is due to sublimation of buried ice. The ice goes directly into a gas (this process is called sublimation) and leaves behind an empty space. Overlying material then collapses into the void.[20] Glaciers are not pure ice; they contain dirt and rocks. At times, they will dump their load of materials into ridges. Such ridges are called moraines. Some places on Mars have groups of ridges that are twisted around; this may have been due to more movement after the ridges were put into place. Sometimes chunks of ice fall from the glacier and get buried in the land surface. When they melt and more or less round hole remains.[21] On Earth we call these features kettles or kettle holes. Mendon Ponds Park in upstate NY has preserved several of these kettles. The picture from HiRISE below shows possible kettles in Moreux Crater.

Climate change caused ice-rich features

Many features on Mars, especially ones found in the Ismenius Lacus quadrangle, are believed to contain large amounts of ice. The most popular model for the origin of the ice is climate change from large changes in the tilt of the planet's rotational axis. At times the tilt has even been greater than 80 degrees[22][23] Large changes in the tilt explains many ice-rich features on Mars.

Studies have shown that when the tilt of Mars reaches 45 degrees from its current 25 degrees, ice is no longer stable at the poles.[24] Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure. This increased pressure allows more dust to be held in the atmosphere. Moisture in the atmosphere will fall as snow or as ice frozen onto dust grains. Calculations suggest this material will concentrate in the mid-latitudes.[25][26] General circulation models of the Martian atmosphere predict accumulations of ice-rich dust in the same areas where ice-rich features are found.[27] When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.[28][28][29] The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.[30] Note, that the smooth surface mantle layer probably represents only relative recent material.

Deltas

Researchers have found a number of examples of deltas that formed in Martian lakes. Deltas are major signs that Mars once had a lot of water because deltas usually require deep water over a long period of time to form. In addition, the water level needs to be stable to keep sediment from washing away. Deltas have been found over a wide geographical range. Below, is a pictures of a one in the Ismenius Lacus quadrangle.[31]

Pits and Cracks

Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits. It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas). After the ice leaves, the ground collapses in the shape of pits and cracks. The pits may come first. When enough pits form, they unite to form cracks.[32]

Other Images from Ismenius Lacus quadrangle

See also

References

  1. ^ 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.
  2. ^ Distances calculated using NASA World Wind measuring tool. http://worldwind.arc.nasa.gov/.
  3. ^ Approximated by integrating latitudinal strips with area of R^2 (L1-L2)(cos(A)dA) from 30° to 65° latitude; where R = 3889 km, A is latitude, and angles expressed in radians. See: http://stackoverflow.com/questions/1340223/calculating-area-enclosed-by-arbitrary-polygon-on-earths-surface.
  4. ^ a b J. Carter, F. Poulet, J.-P. Bibring, and S. Murchie. Detection of Hydrated Silicates in Crustal Outcrops in the Northern Plains of Mars. Science, 2010; 328 (5986): 1682-1686
  5. ^ a b http://www.jpl.nasa.gov/news.cfm?release=2010-209
  6. ^ USGS Gazetteer of Planetary Nomenclature. Mars. http://planetarynames.wr.usgs.gov/.
  7. ^ U.S. department of the Interior U.S. Geological Survey, Topographic Map of the Eastern Region of Mars M 15M 0/270 2AT, 1991
  8. ^ http://space.com/scienceastronomy/090514--mars-rivers.html
  9. ^ http://www.lpi.usra.edu/publications/slidesets/stones/
  10. ^ a b Hugh H. Kieffer (1992). Mars. University of Arizona Press.  
  11. ^ ISBN 0-8165-1247-4
  12. ^ Sharp, R. 1973. Mars Fretted and chaotic terrains. J. Geophys. Res: 78. 4073-4083
  13. ^ http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1053.pdf
  14. ^ a b 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.pdf
  15. ^ Plaut, J., A. Safaeinili,, J. Holt, R. Phillips, J. Head, J., R. Seu, N. Putzig, A. Frigeri. 2009. Radar evidence for ice in lobate debris aprons in the midnorthern latitudes of Mars. Geophys. Res. Lett. 36. doi:10.1029/2008GL036379.
  16. ^ http://www.esa.int/SPECIALS/Mars_Express/SEMBS5V681F_0.html
  17. ^ http://news.discovery.com/space/mars-ice-sheet-climate.html
  18. ^ Madeleine, J. et al. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.
  19. ^ http://www.uahirise.org/ESP_018857_2225
  20. ^ http://hirise.lpl.arizona.edu/PSP_009719_2230
  21. ^ http://hirise.lpl.arizona.edu/PSP_006278_2225
  22. ^ Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars. Science 259, 1294-1297.
  23. ^ Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364.
  24. ^ Levy, J., J. Head, D. Marchant, D. Kowalewski. 2008. Identification of sublimation-type thermal contraction crack polygons at the proposed NASA Phoenix landing site: Implications for substrate properties and climate-driven morphological evolution. Geophys. Res. Lett. 35. doi:10.1029/2007GL032813.
  25. ^ Levy, J., J. Head, D. Marchant. 2009a. Thermal contraction crack polygons on Mars: Classification, distribution, and climate implications from HiRISE observations. J. Geophys. Res. 114. doi:10.1029/2008JE003273.
  26. ^ Hauber, E., D. Reiss, M. Ulrich, F. Preusker, F. Trauthan, M. Zanetti, H. Hiesinger, R. Jaumann, L. Johansson, A. Johnsson, S. Van Gaselt, M. Olvmo. 2011. Landscape evolution in Martian mid-latitude regions: insights from analogous periglacial landforms in Svalbard. In: Balme, M., A. Bargery, C. Gallagher, S. Guta (eds). Martian Geomorphology. Geological Society, London. Special Publications: 356. 111-131
  27. ^ Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364.
  28. ^ a b Mellon, M., B. Jakosky. 1995. The distribution and behavior of Martian ground ice during past and present epochs. J. Geophys. Res. 100, 11781–11799.
  29. ^ Schorghofer, N., 2007. Dynamics of ice ages on Mars. Nature 449, 192–194.
  30. ^ Madeleine, J., F. Forget, J. Head, B. Levrard, F. Montmessin. 2007. Exploring the northern mid-latitude glaciation with a general circulation model. In: Seventh International Conference on Mars. Abstract 3096.
  31. ^ Irwin III, R. et al. 2005. An intense terminal epoch of widespread fluvial activity on early Mars: 2. Increased runoff and paleolake development. Journal of Geophysical Research: 10. E12S15
  32. ^ "HiRISE | Fretted Terrain Valley Traverse (PSP_009719_2230)". Hirise.lpl.arizona.edu. Retrieved December 19, 2010. 


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