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User:Semunm17/Crater counting

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Crater counting is a method for estimating the age of a planet's surface. The method is based upon the assumptions that when a piece of planetary surface is new, then it has no impact craters; impact craters accumulate after that at a rate that is assumed known. Consequently, counting how many craters of various sizes there are in a given area allows determining how long they have accumulated and, consequently, how long ago the surface has formed. The method has been calibrated using the ages obtained by radiometric dating of samples returned from the Moon by the Luna and Apollo missions.[1] It has been used to estimate the age of areas on Mars and other planets that were covered by lava flows, on the Moon of areas covered by giant mares, and how long ago areas on the icy moons of Jupiter and Saturn flooded with new ice.

Crater counting and secondary craters

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What one needs to count using the crater counting method are independent craters. However, not all craters on a given surface are independent: Secondary craters ('secondaries') are craters formed by material excavated by a primary impact that falls back to the surface seconds or minutes later.[2] A way to distinguish primary and secondary craters is to consider their geometric arrangement; for example, large craters often have rays of secondary craters. Secondaries can sometimes also be recognized by their particular shape different from primary craters; this is due to the fact that the excavated material is slower and impacts at a lower angle than asteroids that arrive from space to create the primary crater.

The accuracy of age estimates of geologically young surfaces based on crater counting on Mars has been questioned due to formation of large amounts of secondary craters. In one case, the impact that created Zunil crater produced about a hundred secondary craters, some more than 1000 km from the primary impact. If similar impacts also produced comparable amounts of secondaries, it would mean a particular crater-free area of Mars had not been "splattered by a large, infrequent primary crater", as opposed to suffering relatively few small primary impacts since its formation.[3]High speed ejecta generated from independent craters generates secondary craters which can resemble independent craters as well, contaminating counting processes as the secondary craters appear more circular and less cluttered than typical secondaries. [4] Secondaries will inevitably contaminate independent crater counts leading to some who may question its effectiveness.

History

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The earliest scientist to study and produce a paper using crater counting as an age indicator was Ernst Öpik, an Estonian astronomer and astrophysicist. [5] Ernst Öpik utilized the crater counting method to date the Moon's Mare Imbrium to be approximately 4.5 billion years of age, which was corroborated by isotopic samples. [5] The method was also utilized by Gene Shoemaker and Robert Baldwin, and further improved by Bill Hartman. [6] Hartman's work includes dating the Lunar Mare to be approximately 3.6 billion years old, an age that was in accordance with isotopic samples. [6] In later years, Gerhard Neukum advanced the method by proposing a stable impacting population over the period of 4 billion years due to unchanged shape of crater size-frequency distribution. [7] More recent work has seen the transition from Lunar surface to Martian surface cratering, including work done by Neukum and Hartman. [8] Within the past ten years, the Buffered Crater Counting approach has been used to date geologic formations. [9]The calibration provided by the Lunar samples brought back during the six Apollo missions between 1969 and 1972 has remained invaluable to further refining and advancing the crater counting method to this day, but new work is being done to computerize the crater counting technique using Crater Detection Algorithms. [10][11]

Criticism

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While crater counting has been refined in past years to be an accurate method of determining surface age of a planet despite a lack of isotopic samples, there is dissension in the planetary scientific community concerning the acceptance of crater counting as a precise and accurate form of geochronology. This method is influenced by assumption that at time zero of a planet, the surface had no craters and the craters which followed time zero are spatially and temporally random. It can only be applied with accuracy to planets which have little to no tectonic activity, since constant resurfacing (like on Earth) would distort the true number of craters over time. Planets heavily covered by water or dense atmosphere would also impede the accuracy of this method, since observational efforts would be hampered. Planets with dense atmospheres will also cause meteors to burn up due to friction before impacting the surface of the planet.[12] The Earth is bombarded with approximately 100 tons of space dust, sand, and pebble particles every day; however, most of this material burns up in the atmosphere before ever reaching the surface of the planet. [13] This is common for space material that is smaller than 25 meters, burning up due to friction in the atmosphere. [13] While resulting observational values dating the Lunar surface from Hartman and Öpik do illustrate ages that correspond to isotopic data, they are potentially hampered by observational bias and human error.

Application

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Below is a list of studies which utilize or concern crater counting:

  • Dating very young planetary surfaces from crater statistics: A review of issues and challenges[14]
  • Comparison of different crater counting methods applicated to Parana Valles[15]
  • Crater size-frequency measurements on linear features buffered crater counting in ArcGIS[16]
  • Lunar crater counting lab[17]
  • The Importance of Secondary Cratering to Age Constraints on Planetary Surfaces[18]

See Also

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Further reading

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  • Impact Cratering: A Geologic Process [19]

References

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  1. ^ Che, Xiaochao; Nemchin, Alexander; Liu, Dunyi; Long, Tao; Wang, Chen; Norman, Marc D.; Joy, Katherine H.; Tartese, Romain; Head, James; Jolliff, Bradley; Snape, Joshua F. (2021-11-12). "Age and composition of young basalts on the Moon, measured from samples returned by Chang'e-5". Science. 374 (6569): 887–890. doi:10.1126/science.abl7957. ISSN 0036-8075.
  2. ^ Watters, Wesley A.; Hundal, Carol B.; Radford, Arden; Collins, Gareth S.; Tornabene, Livio L. (2017-07-17). "Dependence of secondary crater characteristics on downrange distance: High-resolution morphometry and simulations". Journal of Geophysical Research: Planets. 122 (8): 1773–1800. doi:10.1002/2017je005295. ISSN 2169-9097.
  3. ^ Kerr, R (2006). "Who can Read the Martian Clock?". Science. 312 (5777): 1132–3. doi:10.1126/science.312.5777.1132. PMID 16728612.
  4. ^ Texas), Lunar and Planetary Science Conference (42 : 2011 : Woodlands, (2011-03-07). Program and abstracts. Lunar and Planetary Institute. OCLC 813618163.{{cite book}}: CS1 maint: date and year (link) CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
  5. ^ a b ÖPIK, E.J. (1971), "Cratering and the Moon's Surface", Advances in Astronomy and Astrophysics, Elsevier, pp. 107–337, retrieved 2021-11-12
  6. ^ a b Bland, Phil (2003-08-01). "Crater counting". Astronomy and Geophysics. 44 (4): 4.21–4.21. doi:10.1046/j.1468-4004.2003.44421.x. ISSN 1366-8781.
  7. ^ Lewis, John S. (1996-09). "Hazards Due to Comets and Asteroids. Edited by Tom Gehrels, Univ. of Arizona Press, Tucson, 1994". Icarus. 123 (1): 245. doi:10.1006/icar.1996.0152. ISSN 0019-1035. {{cite journal}}: Check date values in: |date= (help)
  8. ^ Hartmann, William K.; Neukum, Gerhard (2001), "Cratering Chronology and the Evolution of Mars", Space Sciences Series of ISSI, Dordrecht: Springer Netherlands, pp. 165–194, retrieved 2021-12-10
  9. ^ Kneissl, T.; Michael, G. G.; Platz, T.; Walter, S. H. G. (2015-04-01). "Age determination of linear surface features using the Buffered Crater Counting approach – Case studies of the Sirenum and Fortuna Fossae graben systems on Mars". Icarus. 250: 384–394. doi:10.1016/j.icarus.2014.12.008. ISSN 0019-1035.
  10. ^ Stansbery, Eileen (2016-09-01). "Lunar Rocks and Soils from Apollo Missions". National Aeronautics and Space Administration. Retrieved 2021-12-10.{{cite web}}: CS1 maint: url-status (link)
  11. ^ Lagain, A.; Servis, K.; Benedix, G. K.; Norman, C.; Anderson, S.; Bland, P. A. (2021). "Model Age Derivation of Large Martian Impact Craters, Using Automatic Crater Counting Methods". Earth and Space Science. 8 (2): e2020EA001598. doi:10.1029/2020EA001598. ISSN 2333-5084.
  12. ^ Administrator, NASA Content (2015-03-24). "Asteroid Fast Facts". NASA. Retrieved 2021-11-10.
  13. ^ a b Administrator, NASA Content (2015-03-24). "Asteroid Fast Facts". NASA. Retrieved 2021-12-03.
  14. ^ Williams, Jean-Pierre; Bogert, Carolyn H. van der; Pathare, Asmin V.; Michael, Gregory G.; Kirchoff, Michelle R.; Hiesinger, Harald (2018). "Dating very young planetary surfaces from crater statistics: A review of issues and challenges". Meteoritics & Planetary Science. 53 (4): 554–582. doi:10.1111/maps.12924. ISSN 1945-5100.
  15. ^ Bouley, S.; et al. (2021-11-10). "Comparison of different crater counting methods applicated to Parana Valles" (PDF). Lunar and Planetary Science Conference. 40. {{cite journal}}: Explicit use of et al. in: |first= (help)CS1 maint: extra punctuation (link)
  16. ^ Kneissel, T.; et al. (2021-11-10). "Crater size-frequency measurements on linear features buffered crater counting in ArcGIS" (PDF). Lunar and Planetary Science Conference. 44. {{cite journal}}: Explicit use of et al. in: |first= (help)CS1 maint: extra punctuation (link)
  17. ^ “The Age of the Inner Solar System: Crater Counting Lab.” Lunar and Planetary Institute, 2020.
  18. ^ McEwen, Alfred S.; Bierhaus, Edward B. (2006-05-01). "THE IMPORTANCE OF SECONDARY CRATERING TO AGE CONSTRAINTS ON PLANETARY SURFACES". Annual Review of Earth and Planetary Sciences. 34 (1): 535–567. doi:10.1146/annurev.earth.34.031405.125018. ISSN 0084-6597.
  19. ^ Melosh, H.J. (1989). Impact Cratering: A Geologic Process. New York, New York: Oxford University Press. pp. 3–241. ISBN 0-19-504284-0.
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