Arabia Terra

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THEMIS daytime infrared image mosaic showing Eden Patera (at center), one of the proposed volcanic caldera complexes in Arabia Terra, and its surroundings
Ice sheet in Oxus Patera, a caldera in Arabia Terra. The scalloped nicks along the spines of the caldera's ridges are likely cracks caused by the expansion and contraction of ice.

Arabia Terra is a large upland region in the north of Mars in that lies mostly in the Arabia quadrangle, but a small part is in the Mare Acidalium quadrangle. It is densely cratered and heavily eroded. This battered topography indicates great age, and Arabia Terra is presumed to be one of the oldest terrains on the planet. It covers as much as 4,500 km (2,800 mi) at its longest extent, centered roughly at Lua error in package.lua at line 80: module 'strict' not found. with its eastern and southern regions rising 4 km (13,000 ft) above the north-west. Alongside its many craters, canyons wind through the Arabia Terra, many emptying into the large northern lowlands of the planet, which borders Arabia Terra to the north.

  • MOLA map showing boundaries for Arabia Terra and other nearby regions.

Features

Arabia contains many interesting features. There are some good examples of pedestal craters in the area. A pedestal crater has its ejecta above the surrounding terrain, often forming a steep cliff. The ejecta forms a resistant layer that protects the underlying material from erosion.[1] Mounds and buttes on the floor of some craters display many layers. The layers may have formed by volcanic processes, by wind, or by underwater deposition.[2][3] Dark slope streaks have been observed in Tikhonravov Basin, a large eroded crater. The streaks appear on steep slopes and change over time. At first they are dark, then turn a lighter color, probably by the deposition of fine, light colored dust from the atmosphere.[4] These streaks are thought to form by dust moving downslope in a way similar to snow avalanches on Earth.[5]

Arabia Terra was named in 1979 after a corresponding albedo feature on a map by Giovanni Schiaparelli, who named it in turn after the Arabian peninsula.

Possible tectonism

Research on the region was undertaken in 1997 and the individuality of the province better defined.[6] An equatorial belt was noted with a crater age distinctly younger than the northern part of the province and of Noachis Terra to the south. This was interpreted as an "incipient back-arc system" provoked by the subduction of Mars lowlands under Arabia Terra during Noachian times. Regional fracture patterns were also explained in this manner, and the rotational instability of the planet as a cause was not supported. It contains extension tectonic features[7]

Possible volcanism

A 2013 study proposed that a number of craters within Arabia Terra, including Eden Patera,[8] Euphrates Patera,[9] Siloe Patera,[10] and possibly Semeykin crater,[11] Ismenia Patera,[12] Oxus Patera[13] and Oxus Cavus,[14] represent calderas formed by massive explosive volcanic eruptions[15] (supervolcanoes)[16] of Late Noachian to Early Hesperian age.[17] Termed "plains-style caldera complexes", these very low relief volcanic features appear to be older than the large Hesperian-age shield volcanoes of Tharsis or Elysium. Eden Patera, for example, is an irregular, 55 by 85 km depression up to 1.8 km deep, surrounded by ridged basaltic plains. It contains three linked interior depressions, demarcated by arcuate scarps, that have terraces suggestive of lava lake drainage and faults suggestive of collapse. The features indicative of impact origin that would be expected in an impact crater of comparable diameter and depth are absent.[17] The authors regard crustal thinning due to regional extension to be a more likely explanation for the origin of the volcanic activity than putative subduction.[17] Rapid ascent of magma through the thin crust and a consequent relative absence of degassing may explain the more explosive eruption style associated with these paterae relative to that of the shield volcanoes. The eruptions would have contributed to the layered deposits of Arabia Terra, which are among the fine-grained deposits widespread in the equatorial regions of Mars. Total eruptive volumes of at least 4,600–7,200 km3 per caldera complex (over its history) were inferred.[17]

Recent meteoroid impact

A meteorite impacted in Arabia Terra some time between 30 June 2002 and 5 October 2003. A single small crater of about 22.6 meters (about 74 feet) in diameter is surrounded by light and dark-toned ejecta - indicating that this impact excavated to a depth where light colored strata exists. The crater occurs near 20.6 degrees north latitude, 356.8 degrees west longitude, in Arabia Terra. Images of the area show how the impact site appeared to the Mars Odyssey Thermal Emission Imaging System infrared instrument before and after the impact.[18]

In popular culture

In the novel The Martian by Andy Weir, the protagonist encounters a dust storm in Arabia Terra while traveling from Acidalia Planitia to Schiaparelli crater.[19]

Layers

Many places on Mars show rocks arranged in layers. Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.[20] Layers may be formed by groundwater rising up depositing minerals and cementing sediments. The hardned layers are consequently more protected from erosion. This process may occur instead of layers forming under lakes. <templatestyles src="Module:Hatnote/styles.css"></templatestyles>

Main article: Groundwater on Mars § Layered terrain

A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.[21]

  • Layers in Tikonravev Crater in Arabia, as seen by Mars Global Surveyor (MGS). Layers may form from volcanoes, the wind, or by deposition under water. The craters on the left are pedestal craters. Some researchers believe this crater once held a massive lake.

  • Tikonravev Crater Floor.JPG

    Tikonravev Crater floor, as seen by Mars Global Surveyor. Click on image to see dark slope streaks and layers.

  • Tikhonravov Basin Streaks.JPG

    Tikhonravov Basin streaks, as seen by HiRISE. Scale bar is 500 m (1,600 ft) long

  • Layers in Monument Valley, Arizona. These are accepted as being formed, at least in part, by water deposition. Since Mars contains similar layers, water is considered a major cause of layering on Mars.

  • Henry Crater mound, as seen by HiRISE. The scale bar is 500 m (1,600 ft) long

  • Crater in the middle of Cassini, as seen by HiRISE. Layers may have been deposited under water since it is believed that Cassini once held a giant lake.

  • Buttes, as seen by HiRISE under HiWish program. Buttes have layered rocks with a hard resistant cap rock on the top which protects the underlying rocks from erosion.

  • Possible dikes and layered structures, as seen by HiRISE under HiWish program.

  • Possible fault along a butte, as seen by HiRISE under HiWish program.

Channels

Many places on Mars show channels of different sizes. Many of these channels probably carried water, at least for a time. The climate of Mars may have been such in the past that water ran on its surface. It has been known for some time that Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as our moon stabilizes Earth; at times the tilt has even been greater than 80 degrees[22][23]

  • Channels in Arabia, as seen by CTX This channel winds along for a good distance and has branches. It ends in a depression that may have been a lake at one time.

  • Channel in Arabia, as seen by HiRISE under HiWish program.

  • Channel within larger channel, as seen by HiRISE under HiWish program The existence of the smaller channel suggests water went through the region at least two times in the past.

  • Close-up of channel within larger channel, as seen by HiRISE under HiWish program The existence of the smaller channel suggests water went through the region at least two times in the past. The black box represents the size of a football field. Some parts of the surface would be difficult to walk on with the many small hills and depressions.

  • Sklodowska (Martian crater), as seen by CTX camera (on Mars Reconnaissance Orbiter). Small channels are visible along the eroded, southern rim.

  • Channels in Sklodowska Crater, as seen by CTX camera (on Mars Reconnaissance Orbiter). Note: this is an enlargement of the previous image.

  • Channels in Sklodowska Crater, as seen by HiRISE under the HiWish program.

Upper Plains Unit

Parts of northern Arabia Terra contains the upper plains unit. The Upper Plains Unit is the remnants of a 50-100 meter thick mantling in the mid-latitudes. It was first investigated in the Deuteronilus Mensae (Ismenius Lacus quadrangle) region, but it occurs in other places as well.[24]

Some regions of the upper plains unit display large fractures and troughs with raised rims; such regions are called ribbed upper plains. Fractures are believed to have started with small cracks from stresses. Stress is suggested to initiate the fracture process since ribbed upper plains are common when debris aprons come together or near the edge of debris aprons—such sites would generate compressional stresses. Cracks exposed more surfaces, and consequently more ice in the material sublimates into the planet’s thin atmosphere. Eventually, small cracks become large canyons or troughs.

  • View of stress cracks and larger cracks that have been enlarged by sublimation (ice changing directly into gas) This may be the start of ribbed terrain.

  • Evolution of ribbed terrain from stress cracks—cracks to the left eventually will enlarge and become ribbed terrain toward the right side of picture, as seen by HiRISE under HiWish program

Gallery

  • An oblique view of Arabia Terra produced by Mars Global Surveyor

  • Wikictxp13clifflda.jpg

    Wide view of mesa with CTX showing Cliff face and location of Lobate Debris Apron (LDA) Location is Ismenius Lacus quadrangle.

  • Wikifretesp 028313 2220cliff.jpg

    Enlargement of previous CTX image of mesa This image shows the cliff face and detail in the LDA. Image taken with HiRISE under HiWish program. Location is Ismenius Lacus quadrangle.

  • Pasteur Crater Floor.JPG

    Pasteur Crater floor, as seen by HiRISE. The scale bar is 1,000 m (3,300 ft) long

  • Large group of concentric cracks, as seen by HiRISE, under HiWish program. These may have formed when ice under this place disappeared from the ground.

See also

Notes

  1. ↑ http://hirise.lpl.arizona.edu/PSP_008508_1870
  2. ↑ http://hirise.lpl.arizona.edu/PSP_009008_1915
  3. ↑ http://hirise.lpl.arizona.edu/PSP_004434_1885
  4. ↑ http://hirise.lpl.arizona.edu/PSP_007531_1935
  5. ↑ http://hirise.lpl.arizona.edu/PSP_006569_1915
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Brugman, K., B. Hynek, S. Robbins. 2015. CRATER-BASED TESTS UNLOCK THE MYSTERY OF THE ORIGIN AND EVOLUTION OF ARABIA TERRA, MARS. Lunar and Planetary Science Conference 2359.pdf
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ 17.0 17.1 17.2 17.3 Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ http://www.nasa.gov/mission_pages/mars/images/pia09025.html#.UpGYneIe2E8
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Grotzinger, J. and R. Milliken (eds.). 2012. Sedimentary Geology of Mars. SEPM.
  22. ↑ name= Touma J. and J. Wisdom. 1993. The Chaotic Obliquity of Mars. Science 259, 1294-1297.
  23. ↑ Laskar, J., A. Correia, M. Gastineau, F. Joutel, B. Levrard, and P. Robutel. 2004. Long term evolution and chaotic diffusion of the insolation quantities of Mars. Icarus 170, 343-364.
  24. ↑ Carr, M. 2001.

External links


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