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Applicant -- An investigation of small-body shapes and spins reveal a preferred state of maximum surface stability

Wednesday, April 6, 2016
Jim
Richardson

Over the past twenty years, spacecraft missions, Earth-based radar
experiments, and telescopic observations have revolutionized our knowledge of
Main Belt and near-Earth asteroids. We now possess high resolution shapes,
spin states, and surface properties for a few dozen such objects. Here we
present the results of an examination of 32 small-body shape models, and show
that asteroid shape, gravity, and spin combine to gradually drive the
asteroid towards a condition of maximum surface stability; that is, a state
of low topographic variation (i.e. low surface potential variation), low
slopes, and low surface erosion rates. Of the 32 bodies investigated, 50%
reside within this 'zone of stability', and when asteroid lightcurve
estimates are included, roughly 75% of 1300 well observed asteroids reside
within this zone. This finding indicates that given a mobile surface layer
and sufficient time, small-body surfaces naturally tend to erode towards a
state of minimum topographic variation, which also corresponds to a state of
minimum internal stress. This erosional effect will be most prominent on
bodies several kilometers and larger in size, where YORP induced spin-state
changes are negligible.

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