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Lunar Crater Classification Using Boulder-Crater Ratios

Research on distinguishing primary from secondary craters on the lunar surface based on boulder-crater ratios. The study focuses on the Mare Imbrium region using qualitative and quantitative analysis. Findings reveal eccentric shapes of secondary craters and unevenly distributed boulder sizes. Comparison of primary and secondary craters helps in relative dating of the lunar surface.

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Lunar Crater Classification Using Boulder-Crater Ratios

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  1. Using Boulder Diameter- Crater Diameter Ratios to Differentiate Primary from Secondary Craters on the Lunar Surface Cody Carroll, Ally Fess, and Hannah Adams Kickapoo High School April 1st, 2011

  2. Purpose of Research To distinguish primary craters from secondary craters on the lunar surface using qualitative and quantitative properties.

  3. Study Area: Southeastern Mare Imbrium Lambert Euler Pytheas Between latitudes: 10°N-30°N and longitudes: 20°W-40°W

  4. The Formation of Secondary Craters

  5. Significance of Study Being able to differentiate between primary and secondary craters enables a more accurate method of relative dating of the lunar surface.

  6. Secondary craters, due to the trajectory angles from the primary impact site, should demonstrate a more eccentric shape than primary craters. Secondary craters should have asymmetrical ejecta rays of varying length distributed unevenly around the crater rim. “Ballistics of the Copernican Ray System,” E.M. Shoemaker

  7. Secondary craters shoulddemonstrate a larger ratio of boulder-diameter/ crater-diameter than primary craters. R= Bd/Cd Ruler set in scale of pixels Conversion factor of: .513m/pixel

  8. Boulders of secondary craters should be chaotically distributed and oriented to the downrange region of the crater. M137699035LE

  9. M142421418LE(lower) M144857093RE (bottom) Secondary Primary M144870473LE (upper) M142394256LE Secondary Primary

  10. M144856909LE (lower) M142421418LE (upper) Secondary Primary M144870473LE (near center) M137699035LE (upper) Secondary Primary

  11. Quantitative Data

  12. Quantitative Data

  13. Analysis of Primary Craters(Diameter, Avg. Boulder size, Bd/Cd ratios)

  14. Analysis of Secondary Craters(Diameter, Avg. Boulder size, Bd/Cd ratios)

  15. Comparison of Primary to Secondary Boulder-diameter/ Crater-diameter Ratios *Proximal crater *Proximal crater Distant Secondary Crater- Bd/Cd ratio Primary Crater- Bd/Cd ratio

  16. Differentiating Ejecta Materials M144856909LE

  17. Conclusions • Secondary craters, due to the trajectory angles from the primary impact site, did demonstrate a more eccentric shape than primary craters. • No correlation was observed between secondary craters and asymmetrical ejecta rays of varying length distributed unevenly around the crater rim. • Secondary craters did demonstrate a larger ratio (.02 and above) of boulder-size/ crater-size than primary craters. • Boulders of secondary craters were unevenly distributed and oriented to the downrange region of the crater (within the crater rim or within 60m outside of downrange rim).

  18. References • Bart, Gwendolyn D. and Melosh, H.J. (2007). Using Lunar Boulders to distinguish primary from distant secondary craters. Geophysical Research Letters, Volume 34, L07203. pgs. 1-5 • Shoemaker, E.M. (1960). Ballistics of the Copernican Ray System. Proceedings of Lunar and Planetary Exploratorium Colloquim, Volume 2 Number 2, pgs. 7-20. • McEwen, Alfred S., Preblich, Brandon S. , Turtle, Elizabeth P. , Artemieva, Natalia A. and many others. (2005). The rayed crater Zunil and interpretations of small impact craters on Mars. Retrieved from http://www.sciencedirect.com

  19. Acknowledgements Mr. Andrew Shaner For his providing of Adobe Photoshop for crater/ lunar boulder analysis Dr. Georgiana Kramer for her student mentoring on scientific analysis and conversion of pixel size to distance on imagery Mr. Lynn Coffey For his assistance in formatting of graphical analysis of data

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