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 1 st, 2011

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

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

The Formation of Secondary Craters

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

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

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

M LE (lower) M LE M RE (bottom) M LE (upper) Secondary Primary

M LE (lower) M LE (upper) M LE (upper) M LE (near center) Secondary Primary

Quantitative Data Primary Crater Results Image Number Diameter (m) Average Boulder Diameter (m) Ratio of Crater to Boulder M LE M LE (1) M LE (2) M LE (1) M LE (3) M RE

Quantitative Data Secondary Crater Results Image Number Diameter (m) Average Boulder Diameter (m) Ratio of Crater to Boulder M LE (1) M LE (2) M LE (2) M LE (1) M LE (2) M LE (2) M LE (1) M RE

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

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

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

M LE Differentiating Ejecta Materials

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).

References Bart, Gwendolyn D. and Melosh, H.J. (2007). Using Lunar Boulders to distinguish primary from distant secondary craters. Geophysical Research Letters, Volume 34, L 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 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

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