Development of a Numerical Simulation Method for Rocky Body Impacts and Theoretical Analysis of Asteroidal Shapes (Springer Theses)

Supervisor’s Foreword
Parts of this thesis have been published in the following journal articles:
Acknowledgements
Contents
1 Introduction
	1.1 Asteroids in the Solar System
	1.2 Solar System Formation Scenario
	1.3 Planetesimal or Asteroidal Collisions
		1.3.1 Types of Collisional Outcomes
		1.3.2 Collisions as the Origin of Asteroidal Shapes
	References
2 Method
	2.1 Elastic Dynamics
		2.1.1 Basic Equations for Elastic Dynamics
		2.1.2 Basic Concept of SPH Method
		2.1.3 Equations for Standard SPH Method
		2.1.4 Equations for Godunov SPH Method
		2.1.5 Godunov SPH Method and Tensile Instability
		2.1.6 Time Development Method
	2.2 Tillotson Equation of State
	2.3 Self Gravity
		2.3.1 Self Gravity for SPH Method
		2.3.2 Acceleration Scheme of Computation of Self Gravity
	2.4 Fracture Model
		2.4.1 Concept of Fracture Model
		2.4.2 SPH Implementation of Fracture Model
	2.5 Pressure Dependent Failure Model and Friction Model
		2.5.1 Description of Models
		2.5.2 Test Simulations for Friction Model
	2.6 Parallelization of Simulation Code Using FDPS
	2.7 Summary of Utilized Methods and Parameters
	Appendix: Linear Stability Analysis for Godunov SPH Method
	References
3 Results: Shapes of Impact Outcomes
	3.1 Initial Conditions of Impacts
	3.2 Analysis of Results
	3.3 Equal-Mass and Non-destructive Impacts
		3.3.1 Resolution Dependence on Resultant Shapes
		3.3.2 Mass of the Largest Remnants
		3.3.3 Characteristic Shapes Formed Through Collisions
		3.3.4 Summary of Shapes Formed by Collisions
		3.3.5 Discussion: Thresholds to Distinguish Impacts that Form Each Shape
	3.4 Unequal-Mass and Non-destructive Impacts
		3.4.1 Similar-Mass Impacts
		3.4.2 Impacts with Large Mass Ratios
	3.5 Destructive Impacts
	References
4 Discussion: Collisional History  of Asteroids
	4.1 Connection Between Shapes of Asteroids  and Collisional Environments
		4.1.1 Summary of Shapes of Impact Outcomes
		4.1.2 Impact Velocity and Collisional Environments
		4.1.3 Shapes Formed in the Primordial and Present Environments
	4.2 Comparison with Actual Asteroids
		4.2.1 Databases Utilized in Our Analysis
		4.2.2 Fraction of Family Asteroids
		4.2.3 Shapes of Asteroids Larger Than 100 km
		4.2.4 Shapes of Asteroids Larger Than 10 km
		4.2.5 Direction of Rotation Axis
	References
5 Application: Extremely Elongated Shape Of 1I/`Oumuamua
	5.1 Introduction of 1I/`Oumuamua
	5.2 Initial Conditions of Simulations for 1I/`Oumuamua
	5.3 Results of Simulations for 1I/`Oumuamua
		5.3.1 Equal-Mass Impacts with φd=40°
		5.3.2 Dependence on the Friction Angle
		5.3.3 Dependence on the Mass Ratio
	5.4 Discussion: Environments for 1I/`Oumuamua Formation
		5.4.1 Turbulence
		5.4.2 Size of Larger Bodies
		5.4.3 Survivability of Extremely Elongated Shapes Through Ejection Processes
	References
6 Summary and Future Prospects
	6.1 Summary
		6.1.1 Development of the Numerical Simulation Method
		6.1.2 Asteroidal Shapes Formed Through Collisions
		6.1.3 Comparison with Actual Asteroids
		6.1.4 Formation of Extremely Elongated Shape of 1I/`Oumuamua
	6.2 Future Prospects
		6.2.1 Application to Other Phenomena
		6.2.2 Addition of Other Models
		6.2.3 Comparison with Particle Based Codes
	References