Derek C. Richardson

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Numerical simulations of the collisional disruption of large asteroids show that although the parent body is totally shattered, subsequent gravitational reaccumulation leads to the formation of an entire family of large and small objects with dynamical properties similar to those of the parent body. Simulations were performed in two different collisional(More)
Cassini images of Saturn's small inner satellites (radii of less than approximately 100 kilometers) have yielded their sizes, shapes, and in some cases, topographies and mean densities. This information and numerical N-body simulations of accretionary growth have provided clues to their internal structures and origins. The innermost ring-region satellites(More)
Asteroids with satellites are observed throughout the Solar System, from subkilometre near-Earth asteroid pairs to systems of large and distant bodies in the Kuiper belt. The smallest and closest systems are found among the near-Earth and small inner main-belt asteroids, which typically have rapidly rotating primaries and close secondaries on circular(More)
Asteroid families are groups of small bodies that share certain orbit and spectral properties. More than 20 families have now been identified, each believed to have resulted from the collisional break-up of a large parent body in a regime where gravity controls the outcome of the collision more than the material strength of the rock. The size and velocity(More)
There is increasing evidence that many kilometer-sized bodies in the Solar System are piles of rubble bound together by gravity. We present results from a project to map the parameter space of collisions between kilometer-sized spherical rubble piles. The results will assist in parameterization of collision outcomes for Solar System formation models and(More)
It has been suggested that asteroids between ~100 m and ~100 km in size may be gravitational aggregates of loosely consolidated material. Recently evidence has been mounting to support this idea. Comet breakups, crater chains, doublet craters, giant craters, grooves, asteroid spins, underdense asteroids, asteroid satellites, and unusual asteroid shapes can(More)
Evidence is mounting that asteroids larger than a few hundred metres in diameter are gravitational aggregates of smaller, cohesive pieces. For example, images of 25143 Itokawa show a boulder-strewn surface reminiscent of what might be expected following gravitational reaccumulation of material ejected from a catastrophic impact into a larger body. We have(More)
We describe a new direct numerical method for simulating planetesimal dynamics in which N∼ 106 or more bodies can be evolved simultaneously in three spatial dimensions over hundreds of dynamical times. This represents several orders of magnitude improvement in resolution over previous studies. The advance is made possible through modification of a stable(More)
A tree code method that incorporates a local shearing disc model and fourth-order integration algorithm is applied to the problem of planetary rings, with particular emphasis on the dynamics of Saturn's B ring. The new code, described in detail elsewhere, allows for particle self-gravity, a distribution of particle sizes, and surface friction (particle(More)