Arandas (crater)

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Arandas
Arandas Crater.JPG
Arandas Crater, as seen by HiRISE. Click on image for a better view of North and South Walls, as well as central hills. Scale bar is 1000 meters long.
Planet Mars
Coordinates 42°46′N 15°10′W / 42.77°N 15.17°W / 42.77; -15.17Coordinates: 42°46′N 15°10′W / 42.77°N 15.17°W / 42.77; -15.17
Diameter 25.1 km
Eponym a town in Mexico
Viking orbiter mosaic of Arandas crater
Detail of the ejecta of Arandas crater

Arandas Crater is a crater in the Mare Acidalium quadrangle of Mars, located 42.77° North and 15.17° West. It is 25.1 km in diameter and is named after a town in Mexico.[1]

Gullies are visible in the pictures below. 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,

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.[11] The peak is caused by a rebound of the crater floor following the impact.[12] Sometimes craters expose layers that were buried. Rocks from deep underground are tossed onto the surface. Hence, craters can show us what lies deep under the surface.

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.

See also[edit]

References[edit]

  1. ^ http://planetarynames.wr.usgs.gov/
  2. ^ 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. ^ a b http://www.lpi.usra.edu/publications/slidesets/stones/
  12. ^ Hugh H. Kieffer (1992). Mars. University of Arizona Press. ISBN 978-0-8165-1257-7. Retrieved 7 March 2011.