Margaritifer Sinus quadrangle

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Margaritifer Sinus quadrangle
USGS-Mars-MC-19-MargartiferSinusRegion-mola.png
Map of Margartifer Sinus quadrangle from Mars Orbiter Laser Altimeter (MOLA) data. The highest elevations are red and the lowest are blue.
Coordinates 15°00′S 22°30′W / 15°S 22.5°W / -15; -22.5Coordinates: 15°00′S 22°30′W / 15°S 22.5°W / -15; -22.5
Image of the Margaritifer Sinus Quadrangle (MC-19). Most of the region contains heavily cratered highlands, marked with large expanses of chaotic terrain. In the northwestern part, the major rift zone of Valles Marineris connects with a broad canyon filled with chaotic terrain.

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. This quadrangle shows many signs of past water with evidence of lakes, deltas, ancient rivers, inverted channels, and chaos regions that released water.[2] 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.[3] A low area between Parana Valles and Loire Vallis is believed to have once held a lake.[4][5] The 154 km diameter Holden Crater also once held a lake.[6] Near Holden Crater is a graben, called Erythraea Fossa, that once held a chain of three lakes.[7]

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).

Images[edit]

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


What Opportunity Rover Discovered about Rocks and Minerals at Meridiani Planum[edit]

The rock "Berry Bowl".
This image, taken by the microscopic imager, reveals shiny, spherical objects embedded within the trench wall
"Blueberries" (hematite spheres) on a rocky outcrop at Eagle Crater. Note the merged triplet in the upper left.

Opportunity Rover found that the soil at Meridiani Planum was very similar to the soil at Gusev crater and Ares Vallis; however in many places at Meridiani the soil was covered with round, hard, gray spherules that were named "blueberries."[8] These blueberries were found to be composed almost entirely of the mineral hematite. It was decided that the spectra signal spotted from orbit by Mars Odyssey was produced by these spherules. After further study it was decided that the blueberries were concretions formed in the ground by water.[9] Over time, these concretions weathered from what was overlying rock, and then became concentrated on the surface as a lag deposit. The concentration of spherules in bedrock could have produced the observed blueberry covering from the weathering of as little as one meter of rock.[10][11] Most of the soil consisted of olivine basalt sands that did not come from the local rocks. The sand may have been transported from somewhere else.[12]

Minerals in Dust[edit]

A Mössbauer spectrum was made of the dust that gathered on Opportunity’s capture magnet. The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought. A small amount of olivine was also detected which was interpreted as indicating a long arid period on the planet. On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet.[13] Because the Rock Abrasion Tool (RAT) found it easy to grind into the bedrocks, it is thought that the rocks are much softer than the rocks at Gusev crater.

Bedrock Minerals[edit]

Few rocks were visible on the surface where Opportunity landed, but bedrock that was exposed in craters was examined by the suit of instruments on the Rover.[14] Bedrock rocks were found to be sedimentary rocks with a high concentration of sulfur in the form of calcium and magnesium sulfates. Some of the sulfates that may be present in bedrocks are kieserite, sulfate anhydrate, bassanite, hexahydrite, epsomite, and gypsum. Salts, such as halite, bischofite, antarcticite, bloedite, vanthoffite, or gluberite may also be present.[15][16]

The rocks contained the sulfates had a light tone compared to isolated rocks and rocks examined by landers/rovers at other locations on Mars. The spectra of these light toned rocks, containing hydrated sulfates, were similar to spectra taken by the Thermal Emission Spectrometer on board the Mars Global Surveyor. The same spectrum is found over a large area, so it is believed that water once appeared over a wide region, not just in the area explored by Opportunity Rover.[17]

The Alpha Particle X-ray Spectrometer (APXS) found rather high levels of phosphorus in the rocks. Similar high levels were found by other rovers at Ares Vallis and Gusev Crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich.[18] The minerals in the rocks could have originated by acid weathering of basalt. Because the solubility of phosphorus is related to the solubility of uranium, thorium, and rare earth elements, they are all also expected to be enriched in rocks.[19]

When Opportunity Rover traveled to the rim of Endeavour crater, it soon found a white vein that was later identified as being pure gypsum.[20][21] It was formed when water carrying gypsum in solution deposited the mineral in a crack in the rock. A picture of this vein, called "Homestake" formation, is shown below.

"Homestake" formation 

Evidence for Water[edit]

Cross-bedding features in rock "Last Chance".

Examination of Meridiani rocks found strong evidence for past water. The mineral called jarosite which only forms in water was found in all bedrocks. This discovery proved that water once existed in Meridiani Planum[22] In addition, some rocks showed small laminations (layers) with shapes that are only made by gently flowing water.[23] The first such laminations were found in a rock called "The Dells." Geologists would say that the cross-stratification showed festoon geometry from transport in subaqueous ripples.[16] A picture of cross-stratification, also called cross-bedding, is shown on the left.

Box-shaped holes in some rocks were caused by sulfates forming large crystals, and then when the crystals later dissolved, holes, called vugs, were left behind.[23] The concentration of the element bromine in rocks was highly variable probably because it is very soluble. Water may have concentrated it in places before it evaporated. Another mechanism for concentrating highly-soluble bromine compounds is frost deposition at night that would form very thin films of water that would concentrate bromine in certain spots.[8]

Rock from Impact[edit]

One rock, "Bounce Rock," found sitting on the sandy plains was found to be ejecta from an impact crater. Its chemistry was different than the bedrocks. Containing mostly pyroxene and plagioclase and no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars. Bounce rock received its name by being near an airbag bounce mark.[10]

Meteorites[edit]

Opportunity Rover found meteorites just sitting on the plains. The first one analyzed with Opportunity’s instruments was called "Heatshield Rock," as it was found near where Opportunity’s headshield landed. Examination with the Miniature Thermal Emission Spectrometer (Mini-TES), Mossbauer spectrometer, and APXS lead researchers to, classify it as an IAB meteorite. The APXS determined it was composed of 93% iron and 7% nickel. The cobble named "Fig Tree Barberton" is thought to be a stony or stony-iron meteorite (mesosiderite silicate),[24][25] while "Allan Hills," and "Zhong Shan" may be iron meteorites.

Geological History[edit]

Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation.[10] In the process sulfates were deposited. After sulfates cemented the sediments, hematite concretions grew by precipitation from groundwater. Some sulfates formed into large crystals which later dissolved to leave vugs. Several lines of evidence point toward an arid climate in the past billion years or so, but a climate supporting water, at least for a time, in the distant past.[26]

Vallis[edit]

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.[27][28][29]

Branched streams seen by Viking[edit]

The Viking Orbiters discovered much about water on Mars. Branched streams, studied by the Orbiters in the southern hemisphere, suggested that rain once fell.[27][28][29]

Aureum Chaos[edit]

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.[30] 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.[31] The first image below gives a wide view of the area. The next two images are from the HiRISE image.[32]

Mars Science Laboratory[edit]

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.[33] Miyamoto Crater was in the top 7 sites chosen. Holden Crater is believed to have once been a lake. Actually, it is now believed that it held two lakes.[34] The first was longer lived and was formed from drainage within the crater and precipitation. The last lake began when water damed up in Uzboi Vallis broke through a divide, then rapidly drained into Holden Crater. Because there are rocks meters in diameter on the crater floor, it is thought it was a powerful flood when water flowed into the crater.[6]

Eberswalde Crater contains a delta.[35] 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.[36] 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.[37] Iani Chaos, pictured below, was among the top 33 landing sites. Deposits of hematite and gypsum have been found there.[38] 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.[38] They would like to examine sediment layers.

Inverted relief[edit]

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 deposition 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.[39]

Deltas[edit]

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.[40]

Craters[edit]

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.[41] The peak is caused by a rebound of the crater floor following the impact.[27] 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 likely 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.[42]

Gallery[edit]

See also[edit]

External links[edit]

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. ^ Grotzinger, J. and R. Milliken (eds.) 2012. Sedimentary Geology of Mars. SEPM
  3. ^ 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
  4. ^ Goldspiel, J. and S. Squyres. 2000. Groundwater sapping and valley formation on Mars. Icarus. 89: 176-192. doi:10.1006/icar.2000.6465
  5. ^ Michael H. Carr (2006). The surface of Mars. Cambridge University Press. ISBN 978-0-521-87201-0. Retrieved 21 March 2011. 
  6. ^ a b Cabrol, N. and E. Grin (eds.). 2010. Lakes on Mars. Elsevier. NY.
  7. ^ Buhler, P. et al. 2011. Evidence for palelakes in Erythracea Fossa, Mars: Implications for an ancient hydrological cycle. Icarus. 213: 104-115.
  8. ^ a b Yen, A., et al. 2005. An integrated view of the chemistry and mineralogy of martian soils. Nature. 435.: 49-54.
  9. ^ Bell, J (ed.) The Martian Surface. 2008. Cambridge University Press. ISBN 978-0-521-86698-9
  10. ^ a b c Squyres, S. et al. 2004. The Opportunity Rover’s Athena Science Investigation at Meridiani Planum, Mars. Science: 1698-1703.
  11. ^ Soderblom, L., et al. 2004. Soils of Eagle Crater and Meridiani Planum at the Opportunity Rover Landing Site. Science: 306. 1723-1726.
  12. ^ Christensen, P., et al. Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover. Science: 306. 1733-1739.
  13. ^ Goetz, W., et al. 2005. Indication of drier periods on Mars from the chemistry and mineralogy of atmospheric dust. Nature: 436.62-65.
  14. ^ Bell, J., et al. 2004. Pancam Multispectral Imaging Results from the Opportunity Rover at Meridiani Planum. Science: 306.1703-1708.
  15. ^ Christensen, P., et al. 2004 Mineralogy at Meridiani Planum from the Mini-TES Experiment on the Opportunity Rover. Science: 306. 1733-1739.
  16. ^ a b Squyres, S. et al. 2004. In Situ Evidence for an Ancient Aqueous Environment at Meridian Planum, Mars. Science: 306. 1709-1714.
  17. ^ Hynek, B. 2004. Implications for hydrologic processes on Mars from extensive bedrock outcrops throughout Terra Meridiani. Nature: 431. 156-159.
  18. ^ Dreibus,G. and H. Wanke. 1987. Volatiles on Earth and Marsw: a comparison. Icarus. 71:225-240
  19. ^ Rieder, R., et al. 2004. Chemistry of Rocks and Soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer. Science. 306. 1746-1749
  20. ^ http://www.nasa.gov/mission_pages/mer/news/mer20111207.html
  21. ^ http://www.sciencedaily.com/releases/2012/01/120125093619.htm
  22. ^ Klingelhofer, G. et al. 2004. Jarosite and Hematite at Meridiani Planum from Opportunity’s Mossbauer Spectrometer. Science: 306. 1740-1745.
  23. ^ a b Herkenhoff, K., et al. 2004. Evidence from Opportunity’s Microscopic Imager for Water on Meridian Planum. Science: 306. 1727-1730
  24. ^ Squyres, S., et al. 2009. Exploration of Victoria Crater by the Mars Rover Opportunity. Science: 1058-1061.
  25. ^ Schroder,C., et al. 2008. J. Geophys. Res: 113.
  26. ^ Clark, B. et al. Chemistry and mineralogy of outcrops at Meridiani Planum. Earth Planet. Sci. Lett. 240: 73-94.
  27. ^ a b c Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7. Retrieved 7 March 2011. 
  28. ^ a b Raeburn, P. 1998. Uncovering the Secrets of the Red Planet Mars. National Geographic Society. Washington, D.C.
  29. ^ a b Moore, P. et al. 1990. The Atlas of the Solar System. Mitchell Beazley Publishers, New York.
  30. ^ (HiRISE image; Observation ID: PSP_0040261765)
  31. ^ Captioned Images Inspired by HiWish Suggestions (HiRISE)
  32. ^ Mesas in Aureum Chaos (HiRISE image; Observation ID: ESP_016869_1775)
  33. ^ Next Mars Rover's Landing Site Narrowed to 4 Choices. JR Minkel, 15 June 2010 (SPACE.com)
  34. ^ Grant,J., et al. 2008. HiRISE imaging of impact megabreccia and sub-meter aqueous strata in Holden Crater, Mars. Geology. 36: 195-198.
  35. ^ NASA Narrows List of Next Mars Landing Sites. Irene Klotz, 21 November 2008. (Discovery News)
  36. ^ 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
  37. ^ HiRISE - High Resolution Imaging Science Experiment
  38. ^ a b The Floods of Iani Chaos (Mars Odyssey THEMIS)
  39. ^ Sinuous Ridges Near Aeolis Mensae (HiRISE image; Observation ID: PSP_002279_1735)
  40. ^ 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
  41. ^ Stones, Wind, and Ice: A Guide to Martian Impact Craters. Compiled by Nadine G. Barlow, Virgil L. Sharpton
  42. ^ http://www.nasa.gov/home/hqnews/2011/dec/HQ_11-403_Mars_Rover_Gypsum.html
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Margaritifer