Eridania quadrangle

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Eridania quadrangle
USGS-Mars-MC-29-EridaniaRegion-mola.png
Map of Eridania quadrangle from Mars Orbiter Laser Altimeter (MOLA) data. The highest elevations are red and the lowest are blue.
Coordinates 47°30′S 210°00′W / 47.5°S 210°W / -47.5; -210Coordinates: 47°30′S 210°00′W / 47.5°S 210°W / -47.5; -210
Image of the Eridania Quadrangle (MC-29). The region mainly includes heavily cratered highlands. The west-central part includes Kepler Crater.

The Eridania quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Eridania quadrangle is also referred to as MC-29 (Mars Chart-29).[1]

The Eridania quadrangle lies between 30° and 65° south latitude and 180° and 240° west longitude on the planet Mars. Most of the classic region named Terra Cimmeria is found within this quadrangle. Part of the Electris deposits, a 100–200 meters thick, light-toned deposit covers the Eridania quadrangle.[2] Many slopes in Eridania contain gullies, which are believed to be caused by flowing water.

Martian Gullies[edit]

The Eridania quadrangle is the location of gullies that may be due to recent flowing water. Gullies occur on steep slopes, especially on the walls of craters. Gullies are believed to be relatively young because they have few, if any craters. Moreover, they lie on top of sand dunes which themselves are considered to be quite young. Usually, each gully has an alcove, channel, and apron. Some studies have found that gullies occur on slopes that face all directions,[3] others have found that the greater number of gullies are found on poleward facing slopes, especially from 30-44 S.[4][5]

Although many ideas have been put forward to explain them,[6] the most popular involve liquid water coming from an aquifer, from melting at the base of old glaciers, or from the melting of ice in the ground when the climate was warmer.[7][8] Because of the good possibility that liquid water was involved with their formation and that they could be very young, scientists are excited. Maybe the gullies are where we should go to find life.

There is evidence for all three theories. Most of the gully alcove heads occur at the same level, just as one would expect of an aquifer. Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin.[9] One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layer that allow water to flow. They may consist of porous sandstone. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies.[10] Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah.[11]

As for the next theory, much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust.[12][13][14] This ice-rich mantle, a few yards thick, smooths the land, but in places it has a bumpy texture, resembling the surface of a basketball. The mantle may be like a glacier and under certain conditions the ice that is mixed in the mantle could melt and flow down the slopes and make gullies.[15][16][17] Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE.[18] The ice-rich mantle may be the result of climate changes.[19] Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods, water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor will condense on the particles, then fall down to the ground due to the additional weight of the water coating. When Mars is at its greatest tilt or obliquity, up to 2 cm of ice could be removed from the summer ice cap and deposited at midlatitudes. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick.[20][21] When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulating the remaining ice.[22] Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow.[23][24] Higher elevations have far fewer gullies because ice would tend to sublimate more in the thin air of the higher altitude.[25]

The third theory might be possible since climate changes may be enough to simply allow ice in the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast.[26] Since the gullies occur on steep slopes only a small decrease of the shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough.[27][28] Calculations show that a third of a mm of runoff can be produced each day for 50 days of each Martian year, even under current conditions.[29]

Surface[edit]

Some surfaces in Eridania are covered with a mantling unit that is believed to be water ice-rich. In some places the surface displays a pitted or dissected texture; these textures are suggestive of material that once held ice that has since disappeared allowing the remaining soil to collapse into the subsurface.[30]

Dust devil tracks[edit]

Many areas on Mars, including Eridania, experience the passage of giant dust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface.

Dust devils occur when the sun warms up the air near a flat, dry surface. The warm air then rises quickly through the cooler air and begins spinning while moving ahead. This spinning, moving cell may pick up dust and sand then leave behind a clean surface.[31]

Dust devils have been seen from the ground and high overhead from orbit. They have even blown the dust off of the solar panels of the two Rovers on Mars, thereby greatly extending their lives.[32] The twin Rovers were designed to last for 3 months, instead they lasted more than six years, and one is still going after 8 years. The pattern of the tracks have been shown to change every few months.[33]

A study that combined data from the High Resolution Stereo Camera (HRSC) and the Mars Orbiter Camera (MOC) found that some large dust devils on Mars have a diameter of 700 meters and last at least 26 minutes.[34]

Palemagnetism[edit]

The Mars Global Surveyor (MGS) discovered magnetic stripes in the crust of Mars, especially in the Phaethontis and Eridania quadrangles (Terra Cimmeria and Terra Sirenum).[35][36] The magnetometer on MGS discovered 100 km wide stripes of magnetized crust running roughly parallel for up to 2000 km. These stripes alternate in polarity with the north magnetic pole of one pointing up from the surface and the north magnetic pole of the next pointing down.[37] When similar stripes were discovered on Earth in the 1960s, they were taken as evidence of plate tectonics. Researchers believe these magnetic stripes on Mars are evidence for a short, early period of plate tectonic activity.[38] When the rocks became solid they retained the magnetism that existed at the time. A magnetic field of a planet is believed to be caused by fluid motions under the surface.[39][40][41] However, there are some differences, between the magnetic stripes on Earth and those on Mars. The Martian stripes are wider, much more strongly magnetized, and do not appear to spread out from a middle crustal spreading zone. Because the area containing the magnetic stripes is about 4 billion years old, it is believed that the global magnetic field probably lasted for only the first few hundred million years of Mars' life, when the temperature of the molten iron in the planet's core might have been high enough to mix it into a magnetic dynamo. There are no magnetic fields near large impact basins like Hellas. The shock of the impact may have erased the remnant magnetization in the rock. So, magnetism produced by early fluid motion in the core would not have existed after the impacts.[42]

When molten rock containing magnetic material, such as hematite (Fe2O3), cools and solidifies in the presence of a magnetic field, it becomes magnetized and takes on the polarity of the background field. This magnetism is lost only if the rock is subsequently heated above a particular temperature (the Curie point which is 770°C for iron). The magnetism left in rocks is a record of the magnetic field when the rock solidified.[43]

Gallery[edit]

See also[edit]

External links[edit]

  • [1] Gives a general review of many of the theories involving the origin of gullies.
  • [2] Gives a good review of the history of the discovery of gullies.

References[edit]

  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. ^ Grant, J. and P. Schultz. 1990. Gradational epochs on Mars: Evidence from west-northwest of Isidis Basin and Electric. Icarus: 84. 166-195.
  3. ^ Edgett, K. et al. 2003. Polar-and middle-latitude martian gullies: A view from MGS MOC after 2 Mars years in the mapping orbit. Lunar Planet. Sci. 34. Abstract 1038.
  4. ^ http://www.planetary.brown.edu/pdfs/3138.pdf
  5. ^ Dickson, J. et al. 2007. Martian gullies in the southern mid-latitudes of Mars Evidence for climate-controlled formation of young fluvial features based upon local and global topography. Icarus: 188. 315-323
  6. ^ http://www.psrd.hawaii.edu/Aug03/MartianGullies.html
  7. ^ Heldmann, J. and M. Mellon. Observations of martian gullies and constraints on potential formation mechanisms. 2004. Icarus. 168: 285-304.
  8. ^ Forget, F. et al. 2006. Planet Mars Story of Another World. Praxis Publishing. Chichester, UK.
  9. ^ Heldmann, J. and M. Mellon. 2004. Observations of martian gullies and constraints on potential formation mechanisms. Icarus. 168:285-304
  10. ^ http://www.space.com/scienceastronomy/mars_aquifer_041112.html
  11. ^ Harris, A and E. Tuttle. 1990. Geology of National Parks. Kendall/Hunt Publishing Company. Dubuque, Iowa
  12. ^ Malin, M. and K. Edgett. 2001. Mars Global Surveyor Mars Orbiter Camera: Interplanetary cruse through primary mission. J. Geophys. Res: 106> 23429-23570
  13. ^ Mustard, J. et al. 2001. Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice. Nature: 412. 411-414.
  14. ^ Carr, M. 2001. Mars Global Surveyor observations of fretted terrain. J. Geophys. Res: 106. 23571-23595.
  15. ^ http://www.msnbc.msn.com/id/15702457?
  16. ^ http://www.pnas.org/content/105/36/13258.full
  17. ^ Head, J. et al. 2008. Formation of gullies on Mars: Link to recent climate history and insolation microenvironments implicate surface water flow origin. PNAS: 105. 13258-13263.
  18. ^ Christensen, P. 2003. Formation of recent martian gullies through melting of extensive water-rich snow deposits. Nature: 422. 45-48.
  19. ^ http://news.nationalgeographic.com/news/2008/03/080319-mars-gullies_2.html
  20. ^ Jakosky B. and M. Carr. 1985. Possible precipitation of ice at low latitudes of Mars during periods of high obliquity. Nature: 315. 559-561.
  21. ^ Jakosky, B. et al. 1995. Chaotic obliquity and the nature of the Martian climate. J. Geophys. Res: 100. 1579-1584.
  22. ^ MLA NASA/Jet Propulsion Laboratory (2003, December 18). Mars May Be Emerging From An Ice Age. ScienceDaily. Retrieved February 19, 2009, from http://www.sciencedaily.com /releases/2003/12/031218075443.htmAds by GoogleAdvertise
  23. ^ http://www.planetary.brown.edu/pdfs/3138.pdf
  24. ^ Dickson, J. et al. 2007. Martian gullies in the southern mid-latitudes of Mars Evidence for climate-controlled formation of young fluvial features based upon local and global topography. Icarus: 188. 315-323.
  25. ^ Hecht, M. 2002. Metastability of liquid water on Mars. Icarus: 156. 373-386.
  26. ^ Peulvast, J. Physio-Geo. 18. 87-105.
  27. ^ Costard, F. et al. 2001. Debris Flows on Mars: Analogy with Terrestrial Periglacial Environment and Climatic Implications. Lunar and Planetary Science XXXII (2001). 1534.pdf
  28. ^ http://www.spaceref.com:16090/news/viewpr.html?pid=7124,
  29. ^ Clow, G. 1987. Generation of liquid water on Mars through the melting of a dusty snowpack. Icarus: 72. 93-127.
  30. ^ http://hirise.lpl.arizona.edu/PSP_006736_1325
  31. ^ http://hirise.lpl.arizona.edu/PSP_00481_2410
  32. ^ http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20070412a.html
  33. ^ http://mars.jpl.nasa.gov/spotlight/KenEdgett.html
  34. ^ Reiss, D. et al. 2011. Multitemporal observations of identical active dust devils on Mars with High Resolution Stereo Camera (HRSC) and Mars Orbiter Camera (MOC). Icarus. 215:358-369.
  35. ^ Barlow, N. 2008. Mars: An Introduction to its Interior, Surface and Atmosphere. Cambridge University Press
  36. ^ ISBN 978-0-387-48925-4
  37. ^ ISBN 978-0-521-82956-4
  38. ^ http://www.space.com/scienceastronomy/mars-plate-tectonics-recent-past-110103.html
  39. ^ Connerney, J. et al. 1999. Magnetic lineations in the ancient crust of Mars. Science: 284. 794-798.
  40. ^ Langlais, B. et al. 2004. Crustal magnetic field of Mars. Journal of Geophysical Research. 109: EO2008
  41. ^ Connerney, J. et al. 2005. Tectonic implications of Mars crustal magnetism. Proceedings of the National Academy of Sciences of the USA. 102: 14970-14975
  42. ^ Acuna, M. et al. 1999. Global distribution of crustal magnetization discovered by the Mars Global Surveyor MAG/ER Experiment. Science. 284: 790-793.
  43. ^ http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31028&fbodylongid=645
Mars Quad Map
About this image
MC-29
Eridania