Coprates quadrangle

The Coprates quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Coprates quadrangle is also referred to as MC-18 (Mars Chart-18).[1]

The Coprates quadrangle goes from 45° to 90° west longitude and 0° to 30° south latitude on Mars.

Contents

Valles Marineris Canyon System

Valles Marineris is an exciting place which sports the largest canyon system in the solar system; this great canyon would go almost all the way across the United States. The name for the whole system of canyons is Valles Marineris. Starting at the west with Noctis Labyrinthus in the Phoenicis Lacus quadrangle, the canyon system ends in the Margaritifer Sinus quadrangle with Capri Chasma and Eos Chasma (in the south). The word Chasma has been designated by the International Astronomical Union to refer to an elongate, steep-sided depression. Valles Marineris was discovered by and named for the Mariner 9 mission. Moving east from Noctis Labyrinthus, the canyon splits into two troughs, Tithonium Chasma and Ius Chasma (in the south). In the middle of the system are the very wide valleys of Ophir Chasma (north), Candor Chasma, and Melas Chasma (south). Going farther to the east, one comes to Coprates Chasma. At the end of Coprates Chasma, the valley gets wider to form Capri Chasma in the north and Eos Chasma in the south. The walls of the canyons often contain many layers. The floors of some of the canyons contain large deposits of layered materials. Some researchers believe that the layers were formed when water once filled the canyons.[2][3][4] The canyons are deep as well as long. In places they are 8-10 kilometers deep. Remember the Earth's Grand Canyon is only 1.6 kilometers deep.[5]

In a study published in the journal Geology in August 2009, a group of scientists led by John Adams of the University of Washington in Seattle, proposed that Valles Marineris may have formed from a giant collapse when salts were heated up thereby releasing water which rushed out carrying mud through underground plumbing. One point that supports this idea is that sulfate salts have been found in the area. These salts contain water which comes off when heated. Heat may have been generated by volcanic processes. After all, a number of huge volcanoes are nearby.[6]

Interior layered deposits and sulfate

Parts of the floor of Candor Chasma contains layered deposits that have been termed interior layered deposits (ILD's). These layers may have formed when the whole area was a giant lake. Some places on Mars contain hydrated sulfate deposits. Sulfate formation involves the presence of water. The European Space Agency's Mars Express found possible evidence of the sulfates epsomite and kieserite. Scientists want to visit these areas with robotic rovers.[7]

Layers

Images of rocks in the canyon walls almost always show layers. Some layers appear tougher than others. In the image below of Ganges Chasma Layers, as seen by HiRISE, one can see that the upper, light-toned deposits are eroding much faster than the lower darker layers. Some cliffs on Mars show a few darker layers standing out and often breaking into large pieces; these are thought to be hard volcanic rock instead of soft ash deposits. An example of hard layers is shown below in the picture of layers in the canyon wall in Coprates, as seen by Mars Global Surveyor. Because of its closeness to the Tharsis volcanic region, the rock layers may be made of layer after layer of lava flows, probably mixed with deposits of volcanic ash that fell out of the air following big eruptions. It is likely the rock strata in the walls preserve a long geological history of Mars.[8] Dark layers may be due to dark lava flows. The dark volcanic rock basalt is common on Mars. However, light-toned deposits may have resulted from rivers, lakes, volcanic ash, or wind blown deposits of sand or dust.[9] The Mars Rovers found light-toned rocks to contain sulfates. Probably having been formed in water, sulfate deposits are of great interest to scientists because they may contain traces of ancient life.[10] The Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument found opaline silica in certain strata along and within the Valles Marineris canyon system.[11] Because Iron sulfates were sometimes found near the opaline silica, it is thought that the two deposits were formed with an acid fluid.[12]

Herbes Chasma and hydrated deposits

Herbes Chasma, a large enclosed valley, may have once held water. Hydrated minerals have been found there. It is thought that large-scale underground springs of groundwater at different times burst to the sufrace to form deposits called Light Toned Deposits (LTD's). Some suggest present or fossilized life forms may be found there because the deposits are relatively young.[13]

Nirgal Vallis and sapping

Nirgal Vallis is one of the longest valley network on Mars. It is so large that it is found on more than one quadrangle. Scientists do not know how all the ancient river valleys were formed. There is evidence that instead of rain or snow, the water that formed the valleys originated under ground. One mechanism that has been advanced is sapping.[14] In sapping, the ground just gives away as water comes out. Sapping is common in some desert areas in America's Southwest. Sapping forms alcoves and stubby tributaries. These features are visible in the picture below of Nigal Vallis taken with Mars Odyssey's THEMIS.

Inverted Relief

Some areas of Mars show inverted relief, where features that were once depressions, like streams, are now instead above the surface. These may have been formed when materials, like large rocks, were deposited in low-lying areas, then left behind after erosion (perhaps wind which can not move large rocks) removed much of the surface layers. Other ways of making inverted relief might be lava flowing down a stream bed or materials being cemented by minerals dissolved in water. On Earth, materials cemented by silica are highly resistant to all kinds of erosional forces. Inverted relief in the shape of streams are further evidence of water flowing on the Martian surface in past times. There are many examples of inverted channels near Juventae Chasma; some are shown in the image of Juventae Chasma below.[15][16][17]

Vallis

Vallis (plural valles) is the Latin word for valley. It is used in planetary geology for the naming of landform features on other planets.

Vallis was used for old river valleys that were discovered on Mars, when probes were first sent to Mars. The Viking Orbiters caused a revolution in our ideas about water on Mars; huge river valleys were found in many areas. Space craft cameras showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers.[5][18][19]

Other Features in the Coprates quadrangle

See also

External links

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. ^ McCauley, J. 1978. Geologic map of the Coprates quadrangle of Mars. U.S. Geol. Misc. Inv. Map I-897
  3. ^ Nedell, S., et al. 1987. Origin and evolution of the layered deposits in the Valles Marineris, Mars. Icarus. 70: 409-441.
  4. ^ Weitz, C. and T. Parker. 2000. New evidence that the Valles Marineris interior deposits formed in standing bodies of water. LPSC XXXI. Abstract 1693
  5. ^ a b Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 9780816512577. http://books.google.com/books?id=NoDvAAAAMAAJ. Retrieved 7 March 2011. 
  6. ^ http://www.space.com/scienceastronomy/090825-st-mars-brine.html
  7. ^ http://themis.asu.edu/features/candorchasma
  8. ^ http://themis.asu.edu/features/coprateschasma
  9. ^ http://hirise.lpl.arizona.edu/PSP_005385_1640
  10. ^ http://hirise,lpl.arizona.edu/PSP_007430_1725
  11. ^ Murchie, S. et al. 2009. A synthesis of Martian aqueous mineralogy after 1 Mars year of observations from the Mars Reconnaissance Orbiter. Journal of Geophysical Research: 114.
  12. ^ Milliken, R. et. al. 2008. Opaline silica in young depsoits on Mars. Geology: 847-850
  13. ^ http://www.universetoday.com/2008/12/11/Groundwater May Have Played Important Role in Shaping Mars
  14. ^ http://themis.la.asu.edu/zoom-20030916a.html
  15. ^ http://hirise.lpl.arizona.edu/PSP_006770_1760
  16. ^ Malin, M., et al. 2010. An overview of the 1985-2006 Mars Orbiter Camera science investigation. http://marsjournal.org
  17. ^ www.sciencedirect.com/science/journal/00191035
  18. ^ Raeburn, P. 1998. Uncovering the Secrets of the Red Planet Mars. National Geographic Society. Washington D.C.
  19. ^ Moore, P. et al. 1990. The Atlas of the Solar System. Mitchell Beazley Publishers NY, NY.