Asimov (crater)

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Asimov Crater
Asimov Crater.jpg
Asimov Crater, as seen by HiRISE. Bottom of picture shows southeastern wall of crater. Top of picture is edge of mound that fills most of the crater.
Planet Mars
Coordinates 47°00′S 355°03′W / 47.0°S 355.05°W / -47.0; -355.05Coordinates: 47°00′S 355°03′W / 47.0°S 355.05°W / -47.0; -355.05
Diameter 84.0 km
Eponym Isaac Asimov (1920–1992), an American biochemist and writer

Asimov Crater is an impact crater in the Noachis quadrangle of Mars, located at 47.0° S and 355.05° W. It is 84.0 km in diameter and was named after Isaac Asimov (1920–1992), an American biochemist and writer.[1]

Gullies in Asimov[edit]

Asimov contains many gullies. Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global Surveyor, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape.[2] They are believed to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes which themselves considered to be quite young. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research. As soon as gullies were discovered,[2] researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found.[3] Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water.[4] [5] [6] With continued observations many more changes were found in Gasa Crater and others.[7] With more repeated observations, more and more changes have been found; since the changes occur in the winter and spring, experts are tending to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water. When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes.[8] [9] [10] In some years frost, perhaps as thick as 1 meter,

Why are Craters important?[edit]

The density of impact craters is used to determine the surface ages of Mars and other solar system bodies. [11] 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. [12] Studies on the earth have documented that cracks are produced and that secondary minerals veins are deposited in the cracks.[13] [14] [15] Images from satellites orbiting Mars have detected cracks near impact craters.[16] Great amounts of heat are produced during impacts. The area around a large impact may take hundreds of thousands of years to cool.[17] [18] [19] Many craters once contained lakes. [20] [21] [22] 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. [23] 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. [24]

See also[edit]

References[edit]

  1. ^ http://planetarynames.wr.usgs.gov/Feature/14567
  2. ^ a b Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.
  3. ^ Malin, M., K. Edgett, L. Posiolova, S. McColley, E. Dobrea. 2006. Present-day impact cratering rate and contemporary gully activity on Mars. Science 314, 1573_1577.
  4. ^ Kolb, et al. 2010. Investigating gully flow emplacement mechanisms using apex slopes. Icarus 2008, 132-142.
  5. ^ McEwen, A. et al. 2007. A closer look at water-related geological activity on Mars. Science 317, 1706-1708.
  6. ^ Pelletier, J., et al. 2008. Recent bright gully deposits on Mars wet or dry flow? Geology 36, 211-214.
  7. ^ NASA/Jet Propulsion Laboratory. "NASA orbiter finds new gully channel on Mars." ScienceDaily. ScienceDaily, 22 March 2014. www.sciencedaily.com/releases/2014/03/140322094409.htm
  8. ^ http://www.jpl.nasa.gov/news/news.php?release=2014-226
  9. ^ http://hirise.lpl.arizona.edu/ESP_032078_1420
  10. ^ http://www.space.com/26534-mars-gullies-dry-ice.html?cmpid=557882
  11. ^ http://www.lpi.usra.edu/publications/slidesets/stones/
  12. ^ http://www.indiana.edu/~sierra/papers/2003/Patterson.html.
  13. ^ 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
  14. ^ http://www.ingentaconnect.com/content/arizona/maps/2005/00000040/00000012/art00007
  15. ^ Pirajno, F. 2000. Ore Deposits and Mantle Plumes. Kluwer Academic Publishers. Dordrecht, The Netherlands
  16. ^ 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
  17. ^ name="news.discovery.com"
  18. ^ 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
  19. ^ Segura, T, O. Toon, A. Colaprete, K. Zahnle. 2002. Environmental Effects of Large Impacts on Mars. Science: 298, 1977-1980.
  20. ^ Cabrol, N. and E. Grin. 2001. The Evolution of Lacustrine Environments on Mars: Is Mars Only Hydrologically Dormant? Icarus: 149, 291-328.
  21. ^ Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Distribution and implications for Noachian surface and subsurface hydrology. Icarus: 198, 37-56.
  22. ^ Fassett, C. and J. Head. 2008. Open-basin lakes on Mars: Implications of valley network lakes for the nature of Noachian hydrology.
  23. ^ Wilson, J. A. Grant and A. Howard. 2013. INVENTORY OF EQUATORIAL ALLUVIAL FANS AND DELTAS ON MARS. 44th Lunar and Planetary Science Conference.
  24. ^ Newsom H. , Hagerty J., Thorsos I. 2001. Location and sampling of aqueous and hydrothermal deposits in martian impact craters. Astrobiology: 1, 71-88.