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[15.06] Asteroid Shapes and the Angle of Repose

M. Hammergren (IGPP/LLNL)

There is a growing view among planetary scientists that many if not most of the small bodies of the solar system (including asteroids and comets) are ``rubble piles'' held together by self-gravity rather than material strength.

In several cases, though, the assumption that asteroid rubble piles should conform to figures of hydrostatic equilibrium leads to unrealistically high inferred densities for those objects.

I suggest here that rubble piles should instead be explicitly considered as granular materials, which behave very differently from fluids even on large scales (as anyone who has walked among sand dunes can testify). I demonstrate that even completely cohesionless particulate assemblies can maintain shapes that are significantly different from figures of hydrostatic equilibrium, so long as: 1) the difference between the local surface normal and the local acceleration vector does not exceed the angle of repose; and 2) internal stresses do not crush individual particles.

If the author provided an email address or URL for general inquiries, it is a s follows:

hammer@igpp.llnl.gov

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