Margaritifer Sinus quadrangle

The margaritifer Sinus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred to as MC-19 (Mars Chart-19).[1]

The Margaritifer Sinus quadrangle covers the area from 0° to 45° west longitude and 0° to 30° south latitude on Mars. Margaritifer Sinus contains some of the longest lake-chain systems on Mars, perhaps because of a wetter climate, more groundwater, or some of each factor. The Samara/Himera lake-chain system is about 1800 km long; the Parara/Loire valley network and lake-chain system is about 1100 km long.[2] A low area between Parana Valles and Loire Vallis is believed to have once held a lake.[3][4]

This region of Mars is famous because the Opportunity Rover landed there on January 25, 2004 at 1.94°S and 354.47°E (5.53° W).

This panorama of Eagle crater shows outcroppings which are thought to have water origins.

Contents

Vallis

Vallis (plural valles) is the Latin word for valley. It is used in planetary geology for the naming of valley 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][6][7]

Branched streams seen by Viking

The Viking Orbiters discovered much about water on Mars. Branched streams, studied by the Orbiters in the southern hemisphere, suggested that rain once fell.[5][6][7]

Aureum Chaos

Aureum Chaos is a major canyon system and collapsed area. It is probably a major source of water for large outflow channels.

Large outflow channels on Mars are believed to be caused by catastrophic discharges of ground water. Many of the channels begin in chaotic terrain, where the ground has apparently collapsed. In the collapsed section, blocks of undisturbed material be seen. The OMEGA experiment on Mars Express discovered clay minerals (phyllosilicates) in a variety of places in Aureum Chaos. Clay minerals need water to form, so the area may once have contained large amounts of water.[8] Scientists are interested in determining what parts of Mars contained water because evidence of past or present life may be found there.

On April 1, 2010, NASA released the first images under the HiWish program, with the public suggesting places for HiRISE to photograph. One of the eight locations was Aureum Chaos.[9] The first image below gives a wide view of the area. The next two images are from the HiRISE image.[10]

Mars Science Laboratory

Several sites in the Margaritifer Sinus quadrangle have been proposed as areas to send NASA's next major Mars rover, the Mars Science Laboratory. Both Holden Crater and Eberswalde Crater made the cut to be among the top four.[11] Miyamoto Crater was in the top 7 sites chosen. Holden Crater is believed to have once been a lake.

Eberswalde Crater contains a delta.[12] There is a great deal of evidence that Miyamoto Crater once contained rivers and lakes. Many minerals, such as clays, chlorides, sulfates, and iron oxides, have been discovered there.[13] These minerals are often formed in water. A picture below shows an inverted channel in Miyamoto Crater. Inverted channels formed from accumulated sediments that were cemented by minerals. These channels eroded into the surface, then the whole area was covered over with sediments. When the sediments were later eroded away, the place where the river channel existed remained because the hardened material that was deposited in the channel was resistant to erosion.[14] Iani Chaos, pictured below, was among the top 33 landing sites. Deposits of hematite and gypsum have been found there.[15] Those minerals are usually formed in connection with water.

The aim of the Mars Science Laboratory is to search for signs of ancient life. It is hoped that a later mission could then return samples from sites that the Mars Science Laboratory identified as probably containing remains of life. To safely bring the craft down, a 12 mile wide, smooth, flat circle is needed. Geologists hope to examine places where water once ponded.[15] They would like to examine sediment layers.

Inverted relief

Some places on Mars show inverted relief. In these locations, a stream bed may be a raised feature, instead of a valley. The inverted former stream channels may be caused by the depositon of large rocks or due to cementation. In either case erosion would erode the surrounding land and leave the old channel as a raised ridge because the ridege will be more resistant to erosion. An image below, taken with HiRISE of Miyamoto Crater shows a ridge that is an old channel that has become inverted.[16]

Deltas

Researchers have found a number of examples of deltas that formed in Martian lakes. Finding deltas is a major sign that Mars once had a lot of water. Deltas often require deep water over a long period of time to form. Also, the water level needs to be stable to keep sediment from washing away. Deltas have been found over a wide geographical range. Below, are pictures of a few.[17]

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.[18] The peak is caused by a rebound of the crater floor following the impact.[5] Sometimes craters will display layers. Craters can show us what lies deep under the surface.

In December 2011, Opportunity Rover discovered a vein of gypsum sticking out of the soil along the rim of Endeavour crater.. Tests confirmed that it contained calcium, sulfur, and water. The mineral gypsum is the best match for the data. It likly formed from mineral rich water moving through a crack in the rock. The vein, called "Homestake," is in Mars' Meridiani plain. It could have been produced in conditions more neutral than the harshly acidic conditions indicated by the other sulfate deposits; hence this environment may have been more hospitable for a large variety of living organisms. Homestake is in a zone where the sulfate-rich sedimentary bedrock of the plains meets older, volcanic bedrock exposed at the rim of Endeavour crater.[19]

Gallery

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. ^ Fassett, C. and J. Head III. 2008. Valley network-fed, open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198. 39-56. doi: 10.1016/j.icarus.2008.06.016
  3. ^ Goldspiel, J. and S. Squyres. 2000. Groundwater sapping and valley formation on Mars. Icarus. 89: 176-192. doi: 10.1006/icar.2000.6465
  4. ^ Michael H. Carr (2006). The surface of Mars. Cambridge University Press. ISBN 9780521872010. http://books.google.com/books?id=uLHlJ6sjohwC. Retrieved 21 March 2011. 
  5. ^ a b c Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 9780816512577. http://books.google.com/books?id=NoDvAAAAMAAJ. Retrieved 7 March 2011. 
  6. ^ a b Raeburn, P. 1998. Uncovering the Secrets of the Red Planet Mars. National Geographic Society. Washington, D.C.
  7. ^ a b Moore, P. et al. 1990. The Atlas of the Solar System. Mitchell Beazley Publishers, New York.
  8. ^ (HiRISE image; Observation ID: PSP_0040261765)
  9. ^ Captioned Images Inspired by HiWish Suggestions (HiRISE)
  10. ^ Mesas in Aureum Chaos (HiRISE image; Observation ID: ESP_016869_1775)
  11. ^ Next Mars Rover's Landing Site Narrowed to 4 Choices. JR Minkel, 15 June 2010 (SPACE.com)
  12. ^ NASA Narrows List of Next Mars Landing Sites. Irene Klotz, 21 November 2008. (Discovery News)
  13. ^ 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. doi:10.1029/2009JE003342
  14. ^ HiRISE - High Resolution Imaging Science Experiment
  15. ^ a b The Floods of Iani Chaos (Mars Odyssey THEMIS)
  16. ^ Sinuous Ridges Near Aeolis Mensae (HiRISE image; Observation ID: PSP_002279_1735)
  17. ^ 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
  18. ^ Stones, Wind, and Ice: A Guide to Martian Impact Craters. Compiled by Nadine G. Barlow, Virgil L. Sharpton
  19. ^ http://www.nasa.gov/home/hqnews/2011/dec/HQ_11-403_Mars_Rover_Gypsum.html