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The Tharsis quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Tharis quadrangle is also referred to as MC-9 (Mars Chart-9).[1]

The Tharsis quadrangle covers the area from 90° to 135° west longitude and 0° to 30° north latitude on Mars. The Tharsis quadrangle contains most of a high plateau called Tharsis or the Tharsis Rise. The plateau is about as high as Earth's Mount Everest and about as big in area as all of Europe. Tharsis contains a group of large volcanoes. Olympus Mons is the tallest.[2]

Contents

Volcanoes

Tharsis is a land of great volcanoes. Olympus Mons is the tallest known volcano. Ascraeus Mons and Pavonis Mons are at least 200 miles across and are over six miles above the plateau that they sit on—and, the plateau is three to four miles above the zero altitude of Mars.[3] Pavonis Mons, the middle in a line of three volcanoes, sits at just about dead center on the equator. Mons is a term used for a large raised feature. Tholus is about the same, but smaller. A patera is flatter and like a volcano with a super large opening. Actually, a patera is formed when the top of a volcano collapses because its magma chamber is empty. Crater Lake Oregon was formed that way. Several volcanoes form a straight line in the Tharsis Uplift. Two major ones are in the Tharsus quadrangle: Ascraeus Mons and Pavonis Mons. It has been proposed that these are the result of a hot rising plume in the mantle that was acting below a moving section of the crust of Mars. Such features are common on Earth. For example the chain of Hawaiian Islands were formed by a stationary rising mantle plume covered over by a moving crustal plate.[4]

Tharsis Changed the Climate

Some scientists maintain that the great mass of Tharsis has had great influence on the climate of Mars. Volcanoes give off great amounts of gas when they erupt. The gases are usually water vapor and carbon dioxide. Estimates put the amount of gas released to the atmosphere as enough to make the atmosphere thicker than the Earth's. In addition the water vapor from the volcanoes could have made enough water to place all of Mars under 120 meters of water. Of course, we all know that carbon dioxide is a greenhouse gas. It raises the temperature of a planet by trapping heat in the form of infrared radiation. So the eruption of lava on Tharsis could have made Mars Earth-like in the past. Mars may have once had a much thicker and warmer atmosphere. Oceans and/or lakes may have been present.[5]

Fossa

The Tharsis quadrangle is also home to large troughs (long narrow depressions) called fossae in the geographical language used for Mars. Fossae in this area are Ulysses Fossae, Olympica Fossae, Ceraunius Fossae, and Tractus Fossae. These troughs form when the crust is stretched until it breaks. The stretching can be due to the large weight of a nearby volcano. Fossae/pit craters are common near volcanoes in the Tharsis and Elysium system of volcanoes.[6] A trough often has two breaks with a middle section moving down, leaving steep cliffs along the sides; such a trough is called a graben.[7] Studies have found that on Mars a fault may be as deep as 5 km, that is the break in the rock goes down to 5 km. Moreover, the crack or fault sometimes widens or dialates. This widening causes a void to form with a relatively high volume. When material slides into the void, a pit crater or a pit crater chain forms. Pit craters do not have rims or ejecta around them, like impact craters do. On Mars, individual pit craters can join to form chains or even to form troughs that are sometimes scalloped.[8] Other ideas have been suggested for the formation of fossae and pit craters. 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. Pit craters are not common on Earth. Sinkholes, where the ground falls into a hole (sometimes in the middle of a town) resemble pit craters on Mars. However, on the Earth these holes are caused by limestone being dissolved thereby causing a void.[8][9][10]

Knowledge of the locations and formation mechanisms of pit craters and fossae is important for the future colonization of Mars because they may be reservoirs of water.[11]

Glaciers

Some scientists believe that glaciers exist on many of the volcanoes in Tharsis, including Olympus Mons, Ascraeus Mons, and Pavonis Mons.[12] Ceraunius Tholus may have even had its glaciers melt to form some temporary lakes in the past.[13][14][15][16][17][18][19]

Dark Slope Streaks

Some pictures below show dark streaks: on the slopes on large blocks just to the left of Tharsis Tholus, on Ceraunius Fossae, and on Olympica Fossae. Such streaks are common on Mars. They occur on steep slopes of craters, troughs, and valleys. The streaks are dark at first. They get lighter with age. Sometimes they start in a tiny spot, then spread out and go for hundreds of meters. They have been seen to travel around obstacles, like boulders.[20] It is believed that they are avalanches of bright dust that expose a darker underlying layer. However, several ideas have been advanced to explain them. Some involve water or even the growth of organisms.[21][22][23] The streaks appear in areas covered with dust. Much of the Martian surface is covered with dust. Fine dust settles out of the atmosphere covering everything. We know a lot about this dust because the solar panels of the Mars Rovers get covered with dust, thus reducing the electrical energy. The power of the Rovers has been restored many times by the wind, in the form of dust devils, cleaning the panels and boosting the power.[24] 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 only a slight amount for the Earth. Also, every few years, the entire planet is engulfed in global dust storms. When NASA's Mariner 9 craft arrived there, nothing could be seen through the dust storm.[25][26] Other global dust storms have also been observed, since that time.

Gallery

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. ^ Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.
  3. ^ Norton, O. 2002. Mapping Mars. Picador, New York.
  4. ^ http://dsc.discovery.com/news/2008/12/16/mars-shell-tectonics.html
  5. ^ Hartmann, W. 2003. A Traveler's Guide to Mars. Workman Publishing. NY NY.
  6. ^ Skinner, J., L. Skinner, and J. Kargel. 2007. Re-assessment of Hydrovolcanism-based Resurfacing within the Galaxias Fossae Region of Mars. Lunar and Planetary Science XXXVIII (2007)
  7. ^ http://hirise.lpl.arizona.edu/PSP_008641_2105
  8. ^ a b Wyrick, D., D. Ferrill, D. Sims, and S. Colton. 2003. Distribution, Morphology and Structural Associations of Martian Pit Crater Chains. Lunar and Planetary Science XXXIV (2003)
  9. ^ http://www.swri.edu/4org/d20/DEMPS/planetgeo/planetmars.html
  10. ^ http://www.msss.com/mars_images/moc/2004/01/29/index.html
  11. ^ Ferrill, D., D. Wyrick, A. Morris, D. Sims, and N. Franklin. 2004. Dilational fault slip and pit chain foramtion on Mars 14:10:4-12
  12. ^ http://www.lpi.edu/meetings/polar2003/pdf/8105.pdf
  13. ^ http://www.planetary.brown.edu/pdfs/3408.pdf
  14. ^ http://www.mars.asu/christensen/advancedmarsclass/shean_glaciers_2005.pdf
  15. ^ Head, J. et al. 2005. Tropical to mid-latitude snow and ice accumulation, flow and glaciation on Mars. Nature: 434. 346-350
  16. ^ http://www.marstoday.com/news/viewpr.html?pid=18050
  17. ^ http://news.brown.edu/pressreleases/2008/04/martian-glaciers
  18. ^ 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
  19. ^ 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.pdf
  20. ^ http://www.space.com/image_of_day_080730.html
  21. ^ http://www.spcae.com/scienceastronomy/streaks_mars_021211.html
  22. ^ http://www.space.com/scienceastronomy/streaks_mars_streaks_030328.html
  23. ^ www.space.com/scienceastronomy/mars_
  24. ^ www.sciencedaily.com/releases/2009/02/090217101110.htm
  25. ^ ISBN 0-517-00192-6
  26. ^ ISBN 0-8165-1257-4

External links

  • [1] - for Mars animation of how Tharsis evolved.

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