Understanding regolith motion in various conditions can help interpreting images of asteroid surf... more Understanding regolith motion in various conditions can help interpreting images of asteroid surfaces and designing efficient sampling mechanisms. We first simulated numerically shaking, avalanche processes and tumbler behaviors, with comparisons with laboratory experiments.
We present a new particle-based numerical method for the simulation of granular dynamics, with ap... more We present a new particle-based numerical method for the simulation of granular dynamics, with application to motions of particles (regolith) on small solar system bodies and planetary surfaces [1]. The method employs the parallel N-body tree code pkdgrav [2] to search for collisions and compute particle trajectories. Particle confinement is achieved by combining arbitrary combinations of four provided wall primitives, namely infinite plane, finite disk, infinite cylinder, and finite cylinder, and degenerate cases of these. Various wall movements, including translation, oscillation, and rotation, are supported. Several tests of the method are presented, including a model granular "atmosphere'' that achieves correct energy equipartition, and a series of tumbler simulations that compare favorably with actual laboratory experiments [3]. DCR and SRS acknowledge NASA Grant No. NNX08AM39G and NSF Grant No. AST0524875; KJW, the Poincaré Fellowship at OCA; NM, Thales Alenia Spa...
The regolith-covered surfaces of asteroids preserve records of geophysical processes that have oc... more The regolith-covered surfaces of asteroids preserve records of geophysical processes that have occurred both at their surfaces and sometimes also in their interiors. As a result of the unique micro-gravity environment that these bodies posses, a complex and varied geophysics has given birth to fascinating features that we are just now beginning to understand. The processes that formed such features were first hypothesised through detailed spacecraft observations and have been further studied using theoretical, numerical and experimental methods that often combine several scientific disciplines. These multiple approaches are now merging towards a further understanding of the geophysical states of the surfaces of asteroids. In this chapter we provide a concise summary of what the scientific community has learned so far about the surfaces of these small planetary bodies and the processes that have shaped them. We also discuss the state of the art in terms of experimental techniques and...
ABSTRACT The dynamics of granular materials, such as regolith on asteroid surfaces, has become a ... more ABSTRACT The dynamics of granular materials, such as regolith on asteroid surfaces, has become a field of high interest in planetary science, due to the recent images from spacecraft showing that granular materials are ubiquitous in the Solar System, and to the preparation of sample return space missions by major space agencies (OSIRIS-REx at NASA, Hayabusa 2 at JAXA, and MarcoPolo-R under study at ESA). We have implemented the Hard-Sphere (HSDEM) and Soft-Sphere Discrete Element Method (SSDEM) in the parallel Nbody code pkdgrav ([1], [2]) and present here three of our investigations: low-speed collisions between rubble piles modeled as granular aggregates, low-speed impact cratering on regolith surfaces and landslides on small bodies.
ABSTRACT We carry out N-body simulations of low-speed impact events into beds of granular materia... more ABSTRACT We carry out N-body simulations of low-speed impact events into beds of granular material using two different collisional routines. Boundary effects are explored by simulating over a small variety of confinement conditions and particle sizes.
Surfaces of planets and small bodies in our Solar System are often covered by a layer of granular... more Surfaces of planets and small bodies in our Solar System are often covered by a layer of granular material that can range from a fine regolith to a gravel-like structure of varying depths. Therefore, the dynamics of granular materials is involved in many events occurring during planetary and small-body evolution and contributes to their geological properties. However from planets to
Threats of impact, as well as questions about asteroid origin and formation of our solar system a... more Threats of impact, as well as questions about asteroid origin and formation of our solar system at large, has driven detailed studies of near-Earth asteroids (NEAs). In spite of the highly successful missions visiting the NEAs (433) Eros and (25143) Itokawa, which gathered a wealth of data about their surface and interior, recent developments in the field of NEAs, such
Understanding regolith motion in various conditions can help interpreting images of asteroid surf... more Understanding regolith motion in various conditions can help interpreting images of asteroid surfaces and designing efficient sampling mechanisms. We first simulated numerically shaking, avalanche processes and tumbler behaviors, with comparisons with laboratory experiments.
We present a new particle-based numerical method for the simulation of granular dynamics, with ap... more We present a new particle-based numerical method for the simulation of granular dynamics, with application to motions of particles (regolith) on small solar system bodies and planetary surfaces [1]. The method employs the parallel N-body tree code pkdgrav [2] to search for collisions and compute particle trajectories. Particle confinement is achieved by combining arbitrary combinations of four provided wall primitives, namely infinite plane, finite disk, infinite cylinder, and finite cylinder, and degenerate cases of these. Various wall movements, including translation, oscillation, and rotation, are supported. Several tests of the method are presented, including a model granular "atmosphere'' that achieves correct energy equipartition, and a series of tumbler simulations that compare favorably with actual laboratory experiments [3]. DCR and SRS acknowledge NASA Grant No. NNX08AM39G and NSF Grant No. AST0524875; KJW, the Poincaré Fellowship at OCA; NM, Thales Alenia Spa...
The regolith-covered surfaces of asteroids preserve records of geophysical processes that have oc... more The regolith-covered surfaces of asteroids preserve records of geophysical processes that have occurred both at their surfaces and sometimes also in their interiors. As a result of the unique micro-gravity environment that these bodies posses, a complex and varied geophysics has given birth to fascinating features that we are just now beginning to understand. The processes that formed such features were first hypothesised through detailed spacecraft observations and have been further studied using theoretical, numerical and experimental methods that often combine several scientific disciplines. These multiple approaches are now merging towards a further understanding of the geophysical states of the surfaces of asteroids. In this chapter we provide a concise summary of what the scientific community has learned so far about the surfaces of these small planetary bodies and the processes that have shaped them. We also discuss the state of the art in terms of experimental techniques and...
ABSTRACT The dynamics of granular materials, such as regolith on asteroid surfaces, has become a ... more ABSTRACT The dynamics of granular materials, such as regolith on asteroid surfaces, has become a field of high interest in planetary science, due to the recent images from spacecraft showing that granular materials are ubiquitous in the Solar System, and to the preparation of sample return space missions by major space agencies (OSIRIS-REx at NASA, Hayabusa 2 at JAXA, and MarcoPolo-R under study at ESA). We have implemented the Hard-Sphere (HSDEM) and Soft-Sphere Discrete Element Method (SSDEM) in the parallel Nbody code pkdgrav ([1], [2]) and present here three of our investigations: low-speed collisions between rubble piles modeled as granular aggregates, low-speed impact cratering on regolith surfaces and landslides on small bodies.
ABSTRACT We carry out N-body simulations of low-speed impact events into beds of granular materia... more ABSTRACT We carry out N-body simulations of low-speed impact events into beds of granular material using two different collisional routines. Boundary effects are explored by simulating over a small variety of confinement conditions and particle sizes.
Surfaces of planets and small bodies in our Solar System are often covered by a layer of granular... more Surfaces of planets and small bodies in our Solar System are often covered by a layer of granular material that can range from a fine regolith to a gravel-like structure of varying depths. Therefore, the dynamics of granular materials is involved in many events occurring during planetary and small-body evolution and contributes to their geological properties. However from planets to
Threats of impact, as well as questions about asteroid origin and formation of our solar system a... more Threats of impact, as well as questions about asteroid origin and formation of our solar system at large, has driven detailed studies of near-Earth asteroids (NEAs). In spite of the highly successful missions visiting the NEAs (433) Eros and (25143) Itokawa, which gathered a wealth of data about their surface and interior, recent developments in the field of NEAs, such
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Papers by Naomi Murdoch