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G. J. Consolmagno (Vatican Observatory), L. J Pesonen (Laboratory for Palaeomagnetism, Geological Survey of Finland), D. T. Britt (University of Arizona), G. J. Flynn (SUNY-Plattsburgh), W. Klock (Matin-Luther-Universität Halle-Wittenberg), K. Kuoppamki (Department of Physics, University of Jyväskylä), L. B. Moore (SUNY-Plattsburgh), M. Terho (Laboratory for Palaeomagnetism, Geological Survey of Finland)
Asteroids appear to have significant porosity and that porosity is large enough to affect their internal structure, their fragmentation behavior in impacts, and their collisional lifetimes. The bulk density of Ida at 2.6 ± 0.5 g/cm3 is substantially below the density range of the existing ordinary chondrite bulk density measurements. Recently reported bulk densities of Mathilde at 1.3 ± 0.2 g/cm3, Ceres at 1.8 g/cm3, Phobos at 1.53 ± 0.10 g/cm3, and Deimos at 1.34 ± 0.83 are lower still. In the case of Mathilde and Deimos, these values are lower than the least dense meteorites measured so far. These bulk density values are low even for loose rubble piles. Measurements of meteorite porosity can provide insight on these low asteroid densities. Porosity provides clues to a meteorite's (and, by inference, asteroidal) lithification, compression, shock effects, and collisional history. In addition, porosity can greatly affect a range of asteroid and meteorite physical properties including thermal diffusivity, seismic velocity, cosmic ray exposure, and dielectric permeability. The thermal and seismic effects can in turn affect asteroid internal evolution, metamorphism, shock dissipation, and elastic properties, which can determine whether colliding asteroids accrete or disrupt.
We will present a data base of meteorite and IDP porosities assembled from the measurements of the authors and previously published data. These data represent the most complete porosity data of set extraterrestrial materials assembled to date.
The author(s) of this abstract have provided an email address for comments about the abstract: britt@lpl.arizona.edu