Stratified Ejecta Boulders as Indicators of Layered Plutons on the Lunar Nearside

1. Stratified Ejecta Boulders as Indicators of Layered Plutons on the Lunar Nearside Tori Wilson, Abby Delawder, and Austen Beason Kickapoo High School, Springfield, Missouri March 29th, 2012 “We choose to go to the ‘Poo not because it is easy…. but because it is hard”

2. Purpose of Research To test multiple hypotheses in an attempt to explain the origins of the alternating light and dark layers in stratified ejecta boulders on the lunar nearside

3. Areas of Study Aristarchus 23.7°N, 47.4°W Mare Undarum 7°N, 69°E 400km

4. Significance of Study To provide a better understanding of the heterogeneity of the lunar crust and provide insight to better understand the evolution of the lunar magma ocean by explaining the origins of stratified boulders The above image has been obtained and modified from the following website: M3 - Moon Mineralogy Mapper - Science - Lunar Crust m3.jpl.nasa.gov

5. BackgroundMultiple Hypotheses of Formation a. Pyroclastic Deposits(Weitz, Zanetti) b. Impact Gardening (Zanetti) c. Glassy Crust* (Zanetti, Self) d. Lava Inflation (Self) e . Layered Pluton (Pieters) Image obtained from: http://planetary.org/blog/article/00002980/. [3]

6. Methodology • Analyzed high resolution EDR images containing 23 stratified ejecta blocks obtained by the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) using Adobe Photoshop • Converted pixel size to actual size (.513meters/pixel) • Only observed EDR images with incidence angles between 20 and 60 • Measured boulder size and each individual light and dark layer (in meters). (See next slide) • Measured Albedo value (RGB) (See 2nd slide) • Analyzed the following qualitative and quantitative characteristics of each stratified boulder: • Overall size (meters) of boulder measured at its widest part discordant to layer orientation • Orientation (linearity) of each alternating strata in relation to boulder orientation (qualitative) • Width (meters) of each alternating light and dark layer within a specified boulder • Ratio of dark layer width to total layer width (Light +Dark) Ld / Ld + LL • Albedo value of each individual alternating light and dark layer

7. Methods of Measurement Measuring Size of Boulders and Individual Layers Ruler set in scale of pixels Conversion factor of: 0.513 meters/pixel

8. Methods of Measurement Measuring Albedo Values using RGB Ruler set in scale of pixels Conversion factor of: 0.513 meters/pixel

9. Quantitative Data Aristarchus

11. Quantitative Data Mare Undarum

13. Albedo Values Albedo Values for Highlands Albedo Values for Mare Undarum Albedo Values for Aristarchus Plateau Albedo Values for Mare

14. Qualitative Data Aristarchus M120161915LE 45 m 35 m -Tapered Layers -Cross Bedding and Tapered Layers

15. Qualitative Data Aristarchus M120161915LE Mare Undarum M154799629RE 45 m 18 m -Cross Bedding -Cross Bedding

16. Qualitative Data Mare Undarum M154799629RE 39 m 35 m -Cross Bedding and Enclaves -Cross Bedding

17. Conclusions • Stratified Boulders in both Aristarchus and Mare Undarum demonstrate thicknesses of dark strata that range between 1 meter and 5 meters • Stratified boulders in both Aristarchus and Mare Undarum demonstrate Dark strata-Light strata ratios between .32 and .61 • Measurements of light/ dark strata in both region demonstrate Albedo values that lie between anorthositic highlands and mare basalt values (>60 but < 150) • Several stratified boulders in Aristarchus and Mare Undarum demonstrate cross-bedding, troughing, tapered layers, and enclaves. Characteristics unique to layered plutons.

18. Possible Sources of Error • Distinguishing “exact” boundaries between the dark and light layers was not always evident on downloaded EDR images • - Based upon measurements of similar boulders/ layers conducted by Zanetti, measurements demonstrated a percent error of 4%. • Resolution of EDR imagery did not provide 100% clarity for analysis of boulders 15-20 meters in size. • Downloaded imagery of boulders in Mare Undarum were of lower incidence angles (20) which may have influenced accuracy of albedo measurements of light strata.

19. References [1] Weitz, C. M., Head, J. M., & Pieters, C. M. (1998). Lunar regional dark mantle deposits: Geologic, multispectral, and modeling studies. Journal of Geophysical Research, 22, 725-22, 759. Retrieved from http://www.planetary.brown.edu/pdfs/2053.pdf [2] Malaska, M. (2011, March 29). [Web log message]. Retrieved from http://planetary.org/blog/article/00002980/ [3] Self, S., Thordarson, T., & Keszthelyi, L. (1997). Emplacement of continental flood basalt lava flows. Informally published manuscript, Geology and Geophysics and Hawaii Center for Volcanology, University of Hawaii , Manoa, Honolulu, Hawaii. Retrieved from http://cat.inist.fr/?aModele=afficheN&cpsidt=1623040 [4] Poldervaart, A., & Taubeneck, W. (1959, October). Layered intrusions of willow lake type. Retrieved from http://www.gsabulletin.gsapubs.org [5] Lindsley, D. H., Frost, B. R., Frost, C. D., & Scoates, J. S. (2010). Petrology, geochemistry, and structure of the chugwateranorthosite, laramieanorthosite complex, southeastern wyoming. The Canadian Mineralogist, 48, 887-923. Retrieved from http://faculty.gg.uwyo.edu/cfrost/pdfs/Lindsley_CM_2010.pdf [6] Barbey, P. (2008, March 10). Layering and schlieren in granitoids: A record of interactions between magma emplacement, crystallization and deformation in growing plutons. Retrieved from http://popups.ulg.ac.be/Geol/docannexe.php?id=2714 [7] Zanetti, M., Hiesinger, H., van derBogert, C. H., & Jolliff, B. L. (2011, March). Observation of stratified ejecta blocks at aristarchus crater. 42nd lunar and planetary science conference, The Woodlands, TX. Retrieved from http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2262.pdf [8] Hawke, B. R., Peterson, C. A., Blewett, D. T., Bussey, D. B. J., Lucey, P. G., Taylor, G. J., & Spudis, P. D. (2003). Distribution and modes of occurrence of lunar anorthosite. Journal of Geophysical Research, 108(E6), Retrieved from http://www.spudislunarresources.com/Bibliography/p/77.pdf [9] Williams, J. P., Paige, D. A., & Manning, C. E. (2003). Layering in the wall rock of vallesmarineris: Intrusive and extrusive magmatism. Geophysical Research Letters, 30(12), Retrieved from www2.ess.ucla.edu/~manning/pdfs/w03.pdf [10] Pieters, C. M. (1991). Bullialdus: Strengthening the Case for Lunar Plutons. Geophysical Research Letters , 2129-2132. [11] Maaloe, S. (1978). The Origin of Rhythmic Layering. Mineralogical Magazine , 337-347. [12] Pons, J., Barbey, P., Nachit, H., & Burg, J. (2006). Development of Igneous Layering During Growth of Pluton: The Tar OuateLaccolith (Morocco). Tectonophysics , 271-286. [13] Conrad, M. E., & Naslund, H. R. (1984). Modally-Graded Rhythmic Layering in the Skaergaard Intrusion. Journal of Petrology , 251-269.

20. Acknowledgements Kickapoo High School Art Department for their providing of the Adobe Photoshop C5S program used for analysis of stratified ejecta boulders and their technical expertise on using this program Dr. Georgiana Kramer for her student mentoring on scientific analysis and critique of the methods of science. (“she is the bomb!”) Dr. Brent Garry for his student mentoring on the formation and processes of lava flows Mr. Mike Zanetti for his student mentoring and direction in analysis of the Aristarchus stratified boulders Lynn Coffey for his assistance in formatting of graphical analysis of data