Driven by Affect to Explore Asteroids, the Moon, and Science Education by Jude Viranga Dingatantrige Perera A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved November 2017 by the Graduate Supervisory Committee: Erik Asphaug, Co-Chair Steven Semken, Co-Chair Ariel Anbar Linda Elkins-Tanton Mark Robinson ARIZONA STATE UNIVERSITY December 2017 ©2017 Jude Viranga Dingatantrige Perera All Rights Reserved ABSTRACT Affect is a domain of psychology that includes attitudes, emotions, interests, and values. My own affect influenced the choice of topics for my dissertation. After examining asteroid interiors and the Moon’s thermal evolution, I discuss the role of affect in online science education. I begin with asteroids, which are collections of smaller objects held together by gravity and possibly cohesion. These “rubble-pile” objects may experience the Brazil Nut Effect (BNE). When a collection of particles of similar densities, but of different sizes, is shaken, smaller particles will move parallel to the local gravity vector while larger objects will do the opposite. Thus, when asteroids are shaken by impacts, they may experience the BNE as possibly evidenced by large boulders seen on their surfaces. I found while the BNE is plausible on asteroids, it is confined to only the outer layers. The Moon, which formed with a Lunar Magma Ocean (LMO), is the next topic of this work. The LMO is due to the Moon forming rapidly after a giant impact between the proto-Earth and another planetary body. The first 80% of the LMO solidified rapidly at which point a floatation crust formed and slowed solidification of the remaining LMO. Impact bombardment during this cooling process, while an important component, has not been studied in detail. Impacts considered here are from debris generated during the formation of the Moon. I developed a thermal model that incorporates impacts and find that impacts may have either expedited or delayed LMO solidification. Finally, I return to affect to consider the differences in attitudes towards science between students enrolled in fully-online degree programs and those enrolled in traditional, in-person degree programs. I analyzed pre- and post-course survey data from the online astrobiology course Habitable Worlds. Unlike their traditional program counterparts, students enrolled in online programs started the course with better attitudes towards science and also further changed towards more positive attitudes during the course. Along with important conclusions in three research fields, this work aims to demonstrate the importance of affect in both scientific research and science education. i DEDICATION To all wanderers who are striving to find their way home ii ACKNOWLEDGMENTS This work was possible due to the generous help I received from a wonderful cast. I would like to first thank Erik Asphaug, Steven Semken, Ariel Anbar, Linda Elkins-Tanton, and Mark Robinson for their support as members of my committee. I am extremely grateful to Alan P. Jackson and Chris Mead for patiently and diligently advising me on my three projects. As two excellent researchers, they guided me within my Zone of Proximal Development to improve as a researcher. I would like to thank the following people for pkdgrav, the code used to model asteroid interiors in this work. Desireé Cotto-Figueroa for introducing me to the code, Derek Richardson for allowing me to use the code, Ronald-Louis Ballouz for helping me set up the code, and Stephen Schwartz for his guidance on using the code. For my science education work, I would like to thank Lev Horodyskyj for introducing me to science education research, Sanlyn Buxner for her guidance on the statistical techniques used in this work and David Lopatto for providing benchmark data for the survey used in this work. I am thankful to Alexander Rudolph who taught and mentored me when I was an undergraduate student and encouraged me to pursue a Ph.D. Though a Ph.D. is completed within several years, I know that I was able to complete this degree due to the education I received throughout my life. Thus, I want to thank all my teachers and professors from St. Joseph’s College (Colombo, Sri Lanka), South Pasadena Middle School and South Pasadena High School (South Pasadena, CA), Cal Poly Pomona, University of California, Santa Cruz, and Arizona State University. I want to particularly thank the late James Asher, Don Edberg, Margaret Fullinwider, Paul Groves, Stanley Jayasinghe, Michael Kemp, Dean Papadakis, and Sean Regan. I am also thankful to my aunt Nayani and uncle Samantha for their encouragement and my two sisters Judith and Virangika for their support. Finally, I am grateful to my mom Janaki for transferring her enthusiasm for science to me, which is a large part of why I was able to embark on this journey. iii TABLE OF CONTENTS Page LIST OF TABLES . viii LIST OF FIGURES . xi CHAPTER 1 INTRODUCTION . 1 2 THE SPHERICAL BRAZIL NUT EFFECT AND ITS SIGNIFICANCE TO ASTEROIDS . 7 2.1 Introduction . 7 2.2 Method. 10 2.2.1 pkdgrav ..................................................... 10 2.2.2 Initial Conditions . 11 2.2.3 Simulations . 15 2.2.4 Considerations for comparisons with asteroids . 16 2.2.4.1 The size distribution. 17 2.2.4.2 The shaking model . 17 2.3 Results . 18 2.3.1 The well mixed central region . 19 2.3.2 The effect of friction . 20 2.3.3 Statistical analysis and time evolution . 22 2.4 Discussion . 23 2.4.1 Asteroid surfaces . 23 2.4.2 The well mixed central region . 26 2.4.3 Examining the Driving Mechanism of the Brazil Nut Effect . 27 2.5 Summary and Outlook . 30 3 EFFECT OF RE-IMPACTING DEBRIS ON THE SOLIDIFICATION OF THE LUNAR MAGMA OCEAN . 33 3.1 Introduction . 34 iv CHAPTER Page 3.1.1 Initial Thermal State of the Moon . 34 3.1.2 Re-impacting Debris . 37 3.1.3 Scope of this Work . 38 3.2 Methods . 38 3.2.1 Re-impacting Debris Evolution . 39 3.2.2 Thermal Evolution Code . 42 3.2.2.1 Quench Crust . 46 3.2.2.2 Incorporating Re-impacts . 51 3.2.2.3 Distribution and Redistribution of Crustal Material. 52 3.2.3 Convergence Tests. 53 3.3 Results . 55 3.3.1 Surface Area with Holes . 55 3.3.2 Lunar Magma Ocean Solidification Time . 55 3.3.2.1 Model Parameter Sensitivity . 58 3.3.3 Kinetic Energy Imparted by Re-impacting Debris . 62 3.3.4 Concentrating Floatation Crust into Holes . 64 3.4 Discussion . 65 3.4.1 Reconciling Crust Sample Ages with the Magma Ocean Solidification Time . 65 3.4.2 Implications for the Lunar Surface. 69 3.4.3 Implications for the Lunar Interior and Orbital Evolution . 70 3.5 Conclusions . 71 4 STUDENTS IN FULLY-ONLINE PROGRAMS REPORT MORE POSITIVE ATTITUDES TOWARD SCIENCE THAN STUDENTS IN TRADITIONAL, IN-PERSON PROGRAMS . 73 4.1 Introduction . 74 4.2 Methods . 77 v CHAPTER Page 4.2.1 The course and the studied population. 77 4.2.2 The survey . 79 4.2.3 Factor analysis . 81 4.3 Results . 82 4.3.1 Factor analysis . 82 4.3.2 Factor correlations . 87 4.3.3 Factor scores and factor score changes . 88 4.3.4 Relationships between factor scores and final course grade . 92 4.4 Discussion . 93 4.4.1 What do the factors represent? . 93 4.4.1.1 Science Attitudes factors . 93 4.4.1.2 Benefits factor . 95 4.4.2 Comparisons between o-course and i-course students . 95 4.4.2.1 Factor scores . 95 4.4.2.2 Relationships with course grade . ..