MEASUREMENT OF ADHESION FORCES IN CM2 METEORITE MATERIALS by ZOE ZESZUT Submitted in partial fulfillment of the requirements for the degree of Master of Sciences Department of Earth, Environmental, and Planetary Sciences CASE WESTERN RESERVE UNIVERSITY August, 2017 1 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of Zoe Zeszut candidate for the degree of Master of Sciences Committee Chair Professor Ralph Harvey Committee Member Professor Steven Hauck Committee Member Assistant Professor Zhicheng Jing Date of Defense 13 June 2017 *We also certify that written approval has been obtained for any proprietary material contained therein. 2 Table of Contents 010 INTRODUCTION 012 Asteroids as Planetary Bodies; Factors of the Asteroidal Environment 014 The Role of Adhesion in Granular Asteroids 017 Asteroid Structure and Mineralogy 020 Asteroid Rotation and Evidence for Adhesion 023 Previous Meteorite Studies 025 Estimates of Adhesion 028 Importance of Adhesion in Asteroid Missions, Exploration, Defense, and ISRU 032 Summary 033 METHODS I 033 The Rig 043 METHODS II 043 Sample Materials 045 Test Article Fabrication 050 Sample Loading and Chamber Preparation 054 Test Article Scanning and Cleaning 057 Conducting the Experiment 062 Data Handling 066 RESULTS 066 Presentation of Data 072 Serpentine 079 Siderite 084 Bronzite 089 Olivine 095 FeNi 100 Mineral Summary 101 CM2 Pins 102 CM2 A 106 CM2 B 110 CM2 C 113 CM2 D 117 CM2 E 120 CM2 Summary 123 INTERPRETATION/ANALYSIS 123 Interpretations of Our Data 123 Mineral Adhesion Ranking 128 Hardness vs Adhesion 129 Conductivity vs Adhesion 131 Comparison of CM2 Data 3 135 Comparison of Minerals vs CM2 137 Total Adhesion Runs vs Total Attraction Runs 138 Effects of Pin Angle 141 Effects of Pin Location 151 Hammer Strikes 153 Conversion to Pascals 154 Interpretations of Adhesion and Attraction Observations 157 DISCUSSION 157 Discussion 160 Comparisons to Existing Literature 164 Considerations for Asteroid Material Adhesion with Man Made Materials 166 CONCLUSIONS 166 Future Work 167 Future Improvements 169 Summary 171 APPENDICES 171 Appendix for Introduction 181 Appendix for Methods 210 Appendix for Data 237 BIBLIOGRAPHY 4 List of Tables 020 Table 1 – Mineralogy of CM meteorites, adapted from Howard et al., 2015 026 Table 2 – Hypothesized Values for Adhesion of Asteroid Material 073 Table 3 – Serpentine adhesion and attraction frequencies 073 Table 4 – Serpentine adhesion and attraction magnitudes 080 Table 5 – Siderite adhesion and attraction frequencies 080 Table 6 – Siderite adhesion and attraction magnitudes 085 Table 7 – Bronzite adhesion and attraction frequencies 085 Table 8 – Bronzite adhesion and attraction magnitudes 090 Table 9 – Olivine adhesion and attraction frequencies 090 Table 10 – Olivine adhesion and attraction magnitudes 095 Table 11 – FeNi adhesion and attraction frequencies 095 Table 12 – FeNi adhesion and attraction magnitudes 100 Table 13 – Summary of mineral adhesion data 102 Table 14 – CM2 A adhesion and attraction frequencies 103 Table 15 – CM2 A adhesion and attraction magnitudes 106 Table 16 – CM2 B adhesion and attraction frequencies 107 Table 17 – CM2 B adhesion and attraction magnitudes 110 Table 18 – CM2 C adhesion and attraction frequencies 111 Table 19 – CM2 C adhesion and attraction magnitudes 113 Table 20 – CM2 D adhesion and attraction frequencies 114 Table 21 – CM2 D adhesion and attraction magnitudes 117 Table 22 – CM2 E adhesion and attraction frequencies 118 Table 23 – CM2 E adhesion and attraction magnitudes 120 Table 24 – CM2 summary 124 Table 25 – Frequency and magnitudes of adhesion and attraction for all materials 133 Table 26 – Percentages of runs with adhesion and attraction for CM2 pins 133 Table 27 – Comparison of average CM2 adhesion values by pin angle 136 Table 28 – Ranked material adhesion values 140 Table 29 – Comparison of all average adhesion and attraction values by pin angle 151 Table 30 – Summary of hammer strikes 154 Table 31 - Conversion of forces from uN to Pa 160 Table 32 – Hypothesized Values of Adhesion of Asteroid Material (from table 2), including our results 163 Table 33 – Scaling of adhesion forces (from Scheeres and Sanchez, 2014). 5 List of Figures 012 Figure 1 – A, Graphic of Van der Waals forces; B, Graphic of Electrostatic forces 014 Figure 2 - Image of asteroid Itokawa, adapted from Fujiwara et al., 2006 and Miyamoto, 2013. 022 Figure 3 – Asteroid diameter vs spin rate, from Polishook et al., 2016. 030 Figure 4 – Bruce Willis mitigating an asteroid. 034 Figure 5 – The Adhesion Laboratory at NASA Glenn Research Center 035 Figure 6 – The Adhesion Rig 038 Figure 7 – The Torsion Balance 039 Figure 8 – Pin and Plate test articles 041 Figure 9 – (with panels A-D) Graphic of the Rig’s torsion balance during an adhesion run. 044 Figure 10 – Energy Dispersive Spectroscopy (EDS) image of LON 94101 and table of element composition and abundances to which pins correspond. 045 Figure 11 – Shards of CM2 meteorite mounted in epoxy prior to being cut down into test articles. 047 Figure 12 – Set of pins representing each of the 6 materials tested. 048 Figure 13 – Profilometry scan of pin head 049 Figure 14 – SEM images of pins – CM2 section before use, serpentine section after use, and mosaic of CM2 before use. 052 Figure 15 - Pin and sample holder 055 Figure 16 – Auger Electron Spectroscopy (AES) scans of FeNi pin before and after sputter cleaning 058 Figure 17 – A graph of a typical adhesion run (plate displacement over time) 059 Figure 18 – Notation of positions on plate 059 Figure 19 – Graphic of various pin angles used in testing 060 Figure 20 – Example of a hammer strike test 062 Figure 21 – A complete adhesion test with box around a single run. 064 Figure 22 – Threshold values in the FIND RUN program 065 Figure 23 – A labeled run detected by the FIND RUN program 068 Figure 24 – A complete adhesion test (serpentine) 070 Figure 25 – Outcomes of adhesion runs 072 Figure 26 – Serpentine representative runs 074 Figure 27 – Serpentine standard deviations 075 Figure 28 – Serpentine adhesion and attraction by plate location 079 Figure 29 – Siderite representative runs 081 Figure 30 – Siderite standard deviations 082 Figure 31 – Siderite adhesion and attraction by plate location 084 Figure 32 – Bronzite representative runs 086 Figure 33 – Bronzite standard deviations 087 Figure 34 – Bronzite adhesion and attraction by plate location 089 Figure 35 – Olivine representative runs 091 Figure 36 – Olivine standard deviations 6 092 Figure 37 – Olivine adhesion and attraction by plate location 095 Figure 38 – FeNi representative runs 097 Figure 39 – FeNi standard deviations 098 Figure 40 – FeNi adhesion and attraction by plate location 102 Figure 41 – CM2 A representative runs 104 Figure 42 – CM2 A adhesion and attraction by plate location 106 Figure 43 – CM2 B representative runs 108 Figure 44 – CM2 B adhesion and attraction by plate location 110 Figure 45 – CM2 C representative runs 112 Figure 46 – CM2 C adhesion and attraction by plate location 113 Figure 47 – CM2 D representative runs 115 Figure 48 – CM2 D adhesion and attraction by plate location 117 Figure 49 – CM2 E representative runs 119 Figure 50 – CM2 E adhesion and attraction by plate location 121 Figure 51 – CM2 standard deviations 128 Figure 52 – Adhesion vs Hardness 130 Figure 53 – Adhesion vs Conductivity 142 Figure 54 – SEM composite image of plate 144 Figure 55 – Elemental abundances on the plate regions 145 Figure 56 – All adhesion and attraction detections by plate location 146 Figure 57 – Total runs by plate location 148 Figure 58 – Areas of the plate with preferential adhesion and attraction 149 Figure 59 – All CM2 adhesion and attraction by plate location 153 Figure 60 – Attraction detections after hammer strikes 161 Figure 61 – Ranges of proposed adhesion values (from table 32) 7 Acknowledgments This project would not have been possible without the assistance of the following people. From Case Western Reserve University - Professor Ralph Harvey, project advisor and collaborator - Professor Steven Hauck, committee member - Assistant Professor Zhicheng Jing, committee member - Undergraduate students Brandon Carreno for the preliminary work characterizing our CM2 material, and Patrick Shober for SEM images of CM2 and serpentine pins. From NASA Glenn Research Center - Dr. James Gaier, project lead on the associated SIF project and an adhesion expert - Dr. Julie Kleinhenz, for developing the FIND RUN program and leading the way with all of the new chamber upgrades - Deborah Waters, for always being there to help with opening the chamber and working with samples 8 Measurement of Adhesion Forces in CM2 Meteorite Materials Abstract by Zoe Zeszut With many current and upcoming space missions exploring C-type asteroids, there is a need for understanding the physical properties of asteroid surface material. Adhesion forces (here including cohesion) are a key component of strength in small asteroids. Asteroid models are highly dependent on values for adhesion, but without in-situ or laboratory measurements on appropriate materials, values are assumed or derived. We conducted a series of experiments with NASA Glenn Research Center's “Adhesion Rig” - a custom instrument with a torsion balance in ultrahigh vacuum - to produce the first measurements of adhesion in asteroid-derived materials (CM2 meteorites). Five individual minerals were also tested to evaluate plausible terrestrial analogs for regolith and to understand the relevance of mineralogical variation observed among C-type asteroids. An average adhesion force of 89 μN was measured for CM2s; similar to previous estimates. None of the minerals tested were similar enough to be considered viable analogs. 9 INTRODUCTION There are tens of millions of asteroids throughout the inner solar system, yet for most of these we have minimal information about their physical properties. The vast majority of these asteroids are small (meter scale), and therefore difficult to observe in detail. To date, only a few of the more prominent asteroids, such as Itokawa and Eros, have been observed in a resolved, multi-pixel image. Because the gravity is so weak on these small bodies, adhesive forces are expected to play a stronger role than they do terrestrially. Knowing adhesion values for asteroid material would be useful in many branches of asteroid research. Adhesion is relevant in describing the development of asteroids, modeling and interpreting their current behavior, and extrapolating how these bodies will continue to develop over time. Additionally, knowledge of adhesion is vital to missions. Upcoming missions to asteroids involve landing on and working with surface material with unknown properties. Finally, should the Earth be in the path for a major asteroid impact, knowing more about the adhesion of these bodies can provide the background information needed to implement mitigation strategies. Adhesion/cohesion refers to the attractive forces between materials. Specifically, adhesion is the force between surfaces of different chemical compositions, such as between iron and glass. Cohesion is the force between surfaces of the same composition, such as two pieces of iron. The same principles govern both forces. For the purposes of this report, we will be using “adhesion” to refer to these forces in inhomogeneous natural materials. 10