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There are only a few known main belt (MB) asteroid families with ages greater than 2 Gyr (Brož et al., 2013; Spoto et al., 2015). Estimates based on the family producing collision rate suggest that the lack of > 2 Gyr-old families may be due to a selection bias in current techniques used to identify families. Family fragments disperse in their orbital elements, semi-major axis, a, eccentricity,...
The Asteroid Belt is characterized by the radial mixing of bodies with different physical properties, a very low mass compared to Minimum Mass Solar Nebula expectations and has an excited orbital distribution, with eccentricities and inclinations covering the entire range of values allowed by the constraints of dynamical stability. Models of the evolution of the Asteroid Belt show that the origin...
Asteroid (101955) Bennu, the target of NASA’s OSIRIS-REx sample return mission, is a D≈0.5km diameter low albedo near-Earth object. It has a spectral signature consistent with primitive carbonaceous chondrites, and an orbit similar to that of the Earth. A plausible evolution scenario for Bennu is that it migrated inward across the inner main belt from a low albedo family by Yarkovsky thermal forces...
A new model for terrestrial planet formation (Hansen [2009]. Astrophys. J., 703, 1131–1140; Walsh, K.J., et al. [2011]. Nature, 2011, 206–209) has explored accretion in a truncated protoplanetary disk, and found that such a configuration is able to reproduce the distribution of mass among the planets in the Solar System, especially the Earth/Mars mass ratio, which earlier simulations have generally...
We have calculated the coherence and detectable lifetimes of synthetic near-Earth object (NEO) families created by catastrophic disruption of a progenitor as it suffers a very close Earth approach. The closest or slowest approaches yield the most violent ‘s-class’ disruption events where the largest remaining fragment after disruption and reaccumulation retains less than 50% of the parent’s mass....
The so-called Nysa–Polana complex of asteroids is a diverse and widespread group studied by Cellino et al. (Cellino, A., Zappalà, V., Doressoundiram, A., di Martino, M., Bendjoya, P., Dotto, E., Migliorini, F., 2001. Icarus 152, 225–237) as a dynamically linked asteroid family. It carries the name of two asteroids because it appears to be two overlapping families of different asteroid taxonomies:...
We present results from numerical experiments testing the behavior of cohesionless gravitational aggregates experiencing a gradual increase of angular momentum. The test bodies used in these numerical simulations are gravitational aggregates of different construction, distinguished by the size distribution of the particles constituting them, parameterized in terms of the angle of friction (ϕ). Shape...
We performed numerical simulations of the obliquity evolution of Mars during the Noachian era, at which time the giant planets were on drastically different orbits than today. For the preferred primordial configuration of the planets we find that there are two large zones where the martian obliquity is stable and oscillates with an amplitude lower than 20°. These zones occur at obliquities below 30°...
We present a new particle-based (discrete element) numerical method for the simulation of granular dynamics, with application to motions of particles on small solar system body and planetary surfaces. The method employs the parallel N-body tree code pkdgrav to search for collisions and compute particle trajectories. Collisions are treated as instantaneous point-contact events between rigid spheres...
We present results of a simulation of a steady-state binary near-Earth asteroid (NEA) population. This study combines previous work on tidal disruption of gravitational aggregates [Walsh, K.J., Richardson, D.C., 2006. Icarus 180, 201–216] with a Monte Carlo simulation of NEA planetary encounters. Evolutionary effects include tidal evolution and binary disruption from close planetary encounters. The...
We present the results of our visible and near-IR observations of Comet 9P/Tempel 1 during the Deep Impact encounter. The comet was observed before, during, and after impact from Kitt Peak National Observatory (J, H, K) and Observatorio Astronómico Nacional-San Pedro Mártir, Mexico (B, V, R, I). High time-resolution images in R, J, H, and K the night of impact with a 3.″5 radius aperture revealed...
We present the results of our visible and near-IR observations of Comet 9P/Tempel 1 during the Deep Impact encounter. The comet was observed before, during, and after impact from Kitt Peak National Observatory (J, H, K) and Observatorio Astronómico Nacional-San Pedro Mártir, Mexico (B, V, R, I). High time-resolution images in R, J, H, and K the night of impact with a 3.″5 radius aperture revealed...
We present numerical simulations of near-Earth asteroid (NEA) tidal disruption resulting in bound, mutually orbiting systems. Using a rubble pile model we have constrained the relative likelihoods for possible physical and dynamical properties of the binaries created. Overall 110,500 simulations were run, with each body consisting of ∼1000 particles. The encounter parameters of close approach distance...
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