Wislicenus (crater)

Wislicenus Crater

Quadrangle map of Sinus Sabaeus labeled with major features. Colored rectangles represent image footprints of Mars Global Surveyor.
Planet Mars
Coordinates 18°24′S 348°36′W / 18.4°S 348.6°W / -18.4; -348.6Coordinates: 18°24′S 348°36′W / 18.4°S 348.6°W / -18.4; -348.6
Diameter 139 km
Eponym Walter Wislicenus, a German astronomer (1859-1905)

Wislicenus Crater is an impact crater in the Sinus Sabaeus quadrangle of Mars at 18.4° south latitude and 348.6° west longitude. It is about 139 km in diameter and was named after Walter Wislicenus, a German astronomer (1859–1905).

Layers

Wislicenus Crater Floor, as seen by HiRISE. Erosion on floor has made layers visible.

Wislicenus Crater contains layers, also called strata. Many places on Mars show rocks arranged in layers. Sometimes the layers are of different colors. Light-toned rocks on Mars have been associated with hydraded minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Some layers are probably made up of fine particles because they seem to break up into find dust. Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders. Basalt has been identified on Mars in many places. Instruments on orbiting spacecraft have detected clay (also called phyllosilicates) in some layers. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.[1] Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.[2]

Rock can form layers in a variety of ways. Volcanoes, wind, or water can produce layers.[3]

Why are Craters important?

The density of impact craters is used to determine the surface ages of Mars and other solar system bodies.[4] The older the surface, the more craters present. Crater shapes can reveal the presence of ground ice.

The area around craters may be rich in minerals. On Mars, heat from the impact melts ice in the ground. Water from the melting ice dissolves minerals, and then deposits them in cracks or faults that were produced with the impact. This process, called hydrothermal alteration, is a major way in which ore deposits are produced. The area around Martian craters may be rich in useful ores for the future colonization of Mars.[5] Studies on the earth have documented that cracks are produced and that secondary minerals veins are deposited in the cracks.[6][7][8] Images from satellites orbiting Mars have detected cracks near impact craters.[9] Great amounts of heat are produced during impacts. The area around a large impact may take hundreds of thousands of years to cool.[10][11][12]

Many craters once contained lakes.[13][14][15] Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars.[16] Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.[17]

See also

References

  1. ↑ http://themis.asu.edu/features/nilosyrtis
  2. ↑ http://hirise.lpl.arizona.edu/PSP_004046_2080
  3. ↑ http://hirise.lpl.arizona.edu?PSP_008437_1750
  4. ↑ http://www.lpi.usra.edu/publications/slidesets/stones/
  5. ↑ http://www.indiana.edu/~sierra/papers/2003/Patterson.html.
  6. ↑ Osinski, G, J. Spray, and P. Lee. 2001. Impact-induced hydrothermal activity within the Haughton impact structure, arctic Canada: Generation of a transient, warm, wet oasis. Meteoritics & Planetary Science: 36. 731-745
  7. ↑ http://www.ingentaconnect.com/content/arizona/maps/2005/00000040/00000012/art00007
  8. ↑ Pirajno, F. 2000. Ore Deposits and Mantle Plumes. Kluwer Academic Publishers. Dordrecht, The Netherlands
  9. ↑ Head, J. and J. Mustard. 2006. Breccia Dikes and Crater-Related Faults in Impact Craters on Mars: Erosion and Exposure on the Floor of a 75-km Diameter Crater at the Dichotomy Boundary. Special Issue on Role of Volatiles and Atmospheres on Martian Impact Craters Meteoritics & Planetary Science
  10. ↑ name="news.discovery.com"
  11. ↑ Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2001. Effects of Large Impacts on Mars: Implications for River Formation. American Astronomical Society, DPS meeting#33, #19.08
  12. ↑ Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2002. Environmental Effects of Large Impacts on Mars. Science: 298, 1977-1980.
  13. ↑ Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.
  14. ↑ Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.
  15. ↑ Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology.
  16. ↑ Wilson, J. A. Grant and A. Howard. 2013. INVENTORY OF EQUATORIAL ALLUVIAL FANS AND DELTAS ON MARS. 44th Lunar and Planetary Science Conference.
  17. ↑ Newsom H. , Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.
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