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Using Boulder Diameter- Crater Using Boulder Diameter- Crater Diameter Ratios to Differentiate Diameter Ratios to Differentiate
Primary from Secondary Craters on Primary from Secondary Craters on the Lunar Surfacethe Lunar Surface
Cody Carroll, Ally Fess, and Hannah AdamsCody Carroll, Ally Fess, and Hannah AdamsKickapoo High School Kickapoo High School
April 1April 1stst, 2011, 2011
Purpose of ResearchPurpose of Research To distinguish primary craters from secondary craters on the
lunar surface using qualitative and quantitative properties.
Study Area: Southeastern Mare ImbriumStudy Area: Southeastern Mare Imbrium
Pytheas
Lambert
Euler
Between latitudes: 10°N-30°N and longitudes: 20°W-40°W
Significance of StudySignificance of Study Being able to differentiate between primary and secondary Being able to differentiate between primary and secondary
craters enables a more accurate method of relative dating craters enables a more accurate method of relative dating of the lunar surface.of the lunar surface.
Secondary craters, due to the trajectory angles from the Secondary craters, due to the trajectory angles from the primary impact site, should demonstrate a more primary impact site, should demonstrate a more eccentric shape than primary craters.eccentric shape than primary craters.
“Ballistics of the Copernican Ray System,” E.M. Shoemaker
Secondary craters should have asymmetrical ejecta Secondary craters should have asymmetrical ejecta rays of varying length distributed unevenly around the rays of varying length distributed unevenly around the crater rim.crater rim.
Ruler set in scale of pixels
Secondary craters should demonstrate a larger ratio of boulder-diameter/
crater-diameter than primary craters.
Conversion factor of: .513m/pixel
R= Bd/Cd
M137699035LE
Boulders of secondary craters should be chaotically Boulders of secondary craters should be chaotically distributed and oriented to the downrange region of the distributed and oriented to the downrange region of the
crater. crater.
M142421418LE (lower)
M142394256LE
M144857093RE (bottom)
M144870473LE (upper)
Secondary Primary
Secondary Primary
M144856909LE (lower)
M137699035LE (upper)
M142421418LE (upper)
M144870473LE (near center)
Secondary Primary
Secondary Primary
Quantitative DataQuantitative Data Primary Crater
Results
Image NumberDiameter
(m)Average Boulder
Diameter (m)Ratio of Crater to
Boulder
M142394256LE 410 1.846 0.0045
M142421418LE (1) 651.51 12.302 0.018
M144856909LE (2) 800 6.4125 0.008
M144870473LE (1) 461.7 5.8482 0.01266
M144870473LE (3) 220.59 3.8475 0.01744
M144857093RE 605.34 5.8995 0.009745
Quantitative DataQuantitative Data
Secondary Crater Results
Image NumberDiameter
(m)Average Boulder
Diameter (m)Ratio of Crater to
Boulder
M137699035LE (1) 117.99 2.975 0.0252
M137699035LE (2) 292.41 6.158 0.0215
M142421418LE (2) 123.12 3.249 0.0302
M144856909LE (1) 548.91 39.501 0.0719
M144856909LE (2) 513 10.26 0.02
M144870473LE (2) 143 4.8936 0.03
M144857093LE (1) 107.73 2.949 0.027
M144857093RE 104.652 5.892 0.0558
Analysis of Primary CratersAnalysis of Primary Craters(Diameter, Avg. Boulder size, Bd/Cd ratios)(Diameter, Avg. Boulder size, Bd/Cd ratios)
410651.51 800
461.7
220.59
605.34
1.846
12.302
6.4125 5.84823.8475
5.8995
0.0045
0.018
0.0080.01266
0.01744
0.009745
0.001
0.01
0.1
1
10
100
1000
0 1 2 3 4 5 6 7
Primary Crater ResultsDiameter (m)
Primary Crater ResultsAverage BoulderDiameter (m)
Primary Crater ResultsRatio of Crater-size toBoulder-size (PrimaryCraters)
117.99
292.41
123.12
548.91 513
143107.73 104.652
2.975
6.158
39.501
10.26
4.8936
2.949
5.892
0.02520.0215
0.0302 0.03
0.0558
3.249
0.0719
0.0270.02
0.01
0.1
1
10
100
1000
0 1 2 3 4 5 6 7 8 9
Secondary Crater ResultsDiameter (m)
Secondary Crater ResultsAverage Boulder Diameter (m)
Secondary Crater Results Ratioof Crater-size to Boulder-size(Secondary Craters)
Analysis of Secondary CratersAnalysis of Secondary Craters(Diameter, Avg. Boulder size, Bd/Cd ratios)(Diameter, Avg. Boulder size, Bd/Cd ratios)
0.0045
0.018
0.008
0.01266
0.01744
0.009745
0.02520.0215
0.0302
0.0719
0.02
0.030.027
0.0558
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0 2 4 6 8 10
Comparison of Primary to Secondary Comparison of Primary to Secondary Boulder-diameter/ Crater-diameter RatiosBoulder-diameter/ Crater-diameter Ratios
Primary Crater- Bd/Cd ratio
Distant Secondary Crater- Bd/Cd ratio
*Proximal crater
*Proximal crater
ConclusionsConclusions
• 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).
ReferencesReferences • 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
AcknowledgementsAcknowledgements
• 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