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

The Formation of The Formation of

Secondary CratersSecondary Craters

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

M144856909LE

Differentiating Ejecta Materials

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