Penticton (crater)

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Penticton
Planet Mars
Region Hellas quadrangle
Coordinates 38°21′S 263°21′W / 38.35°S 263.35°W / -38.35; -263.35Coordinates: 38°21′S 263°21′W / 38.35°S 263.35°W / -38.35; -263.35
Diameter 8 kilometres (5 mi)
Eponym Penticton

Penticton Crater is an impact crater in the Hellas quadrangle of Mars, located at 38.35° south latitude and 263.35° west longitude. It is 8 km in diameter and was named after a Town in British Columbia, Canada,[1] nearby the little town of Okanagan Falls where is located the Dominion Radio Astrophysical Observatory.[2] Images with HiRISE show gullies which were once thought to be caused by flowing water.

Penticton is famous with Mars geologists because evidence for recent flowing liquid was found there. The Mars Reconnaissance Orbiter discovered changes on the wall of Penticton Crater between 1999 and 2004. One interpretation of the changes was that they were caused by water flowing on the surface.[3] A further analysis, published about a year later, revealed that the deposit could have been caused by gravity moving material downslope. The slope where the deposit was sighted was close to the stability limits of dry, unconsolidated materials.[4]

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.[5] 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, location 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,[5] researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found.[6] Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water.[7][8][9] With continued observations many more changes were found in Gasa Crater and others.[10] 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.[11][12][13] 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.[14] The older the surface, the more craters present. Crater shapes can reveal the presence of ground ice.

See also[edit]

References[edit]

  1. ^ "Gazetteer of Planetary Nomenclature | Penticton". usgs.gov. International Astronomical Union. Retrieved 4 March 2015. 
  2. ^ Dominion Radio Astrophysical Observatory
  3. ^ Malin, M. C.; Edgett, K. S.; Posiolova, L. V.; McColley, S. M. et al. (2006). "Present-Day Impact Cratering Rate and Contemporary Gully Activity on Mars". Science 314 (5805): 1573–1577. Bibcode:2006Sci...314.1573M. doi:10.1126/science.1135156. PMID 17158321. 
  4. ^ McEwen, AS; Hansen, CJ; Delamere, WA; Eliason, EM; Herkenhoff, KE; Keszthelyi, L; Gulick, VC; Kirk, RL et al. (2007). "A Closer Look at Water-Related Geologic Activity on Mars". Science 317 (5845): 1706–1709. Bibcode:2007Sci...317.1706M. doi:10.1126/science.1143987. PMID 17885125. 
  5. ^ a b Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and surface runoff on Mars. Science 288, 2330–2335.
  6. ^ 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.
  7. ^ Kolb, et al. 2010. Investigating gully flow emplacement mechanisms using apex slopes. Icarus 2008, 132-142.
  8. ^ McEwen, A. et al. 2007. A closer look at water-related geological activity on Mars. Science 317, 1706-1708.
  9. ^ Pelletier, J., et al. 2008. Recent bright gully deposits on Mars wet or dry flow? Geology 36, 211-214.
  10. ^ 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
  11. ^ http://www.jpl.nasa.gov/news/news.php?release=2014-226
  12. ^ http://hirise.lpl.arizona.edu/ESP_032078_1420
  13. ^ http://www.space.com/26534-mars-gullies-dry-ice.html?cmpid=557882
  14. ^ http://www.lpi.usra.edu/publications/slidesets/stones/