INTERNAL STRUCTURE OF ASTEROIDS HAVING SURFACE SHEDDING DUE TO ROTATIONAL INSTABILITY

ABSTRACT Surface shedding of an asteroid is a failure mode where surface materials fly off due to strong centrifugal forces beyond the critical spin period, while the internal structure does not deform significantly. This paper proposes a possible structure of an asteroid interior that leads to surf...

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Bibliographic Details
Published in:The Astrophysical journal 2015-07, Vol.808 (1), p.1-12
Main Authors: Hirabayashi, Masatoshi, Sánchez, Diego Paul, Scheeres, Daniel J.
Format: Article
Language:English
Subjects:
ASTEROIDS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BULK DENSITY
COMPUTERIZED SIMULATION
Constants
DEFORMATION
Failure
Failure modes
FRICTION
INSTABILITY
minor planets, asteroids: general
PLANETS
Progenitors (astrophysics)
ROTATION
Shedding
SPHERES
SPHEROIDS
SURFACES
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Summary:ABSTRACT Surface shedding of an asteroid is a failure mode where surface materials fly off due to strong centrifugal forces beyond the critical spin period, while the internal structure does not deform significantly. This paper proposes a possible structure of an asteroid interior that leads to surface shedding due to rapid rotation rates. A rubble pile asteroid is modeled as a spheroid composed of a surface shell and a concentric internal core, the entire assembly called the test body. The test body is assumed to be uniformly rotating around a constant rotation axis. We also assume that while the bulk density and the friction angle are constant, the cohesion of the surface shell is different from that of the internal core. First, developing an analytical model based on limit analysis, we provide the upper and lower bounds for the actual surface shedding condition. Second, we use a Soft-sphere Discrete Element Method (SSDEM) to study dynamical deformation of the test body due to a quasi-static spin-up. In this paper we show the consistency of both approaches. Additionally, the SSDEM simulations show that the initial failure always occurs locally and not globally. In addition, as the core becomes larger, the size of lofted components becomes smaller. These results imply that if there is a strong core in a progenitor body, surface shedding is the most likely failure mode.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/808/1/63