Physics
Scientific paper
May 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001agusm...p22b02d&link_type=abstract
American Geophysical Union, Spring Meeting 2001, abstract #P22B-02
Physics
5475 Tectonics (8149), 6205 Asteroids And Meteoroids
Scientific paper
The finite element method is utilized to explore the notion that thermal stresses may represent a largely unrecognized source of tectonism on asteroids. Rapid changes in the average surface temperature of an asteroid, such as may occur during orbital migration events, can induce thermal stresses when the timescale for surface temperature change is comparable to or less than the thermal diffusion time of the asteroid. For a rapid surface temperature increase (corresponding to inward orbital migration), propagation of a thermal wave produces differential heating and thermal expansion of the asteroid. The resulting differential volumetric changes produce compressive thermal stresses near the surface and tensile thermal stresses in the interior. If the yield strength of the material is exceeded, brittle failure can relieve the induced thermal stresses. Consequently as the asteroid equilibrates to its new surface temperature, a new thermal stress regime forms with the opposite sense of the original stress regime (i.e., near-surface stresses change from compressive to tensile). Although the magnitude of the stresses depends on material parameters, asteroid size, and the timescale of surface temperature change, the orientation of the surface principal stresses, and hence the orientation of any resultant tectonic features, is a strong function of asteroid shape. Here, we apply this model for thermal stresses in asteroids to 433 Eros. The NEAR Shoemaker spacecraft has revealed a pervasive network of lineations on Eros. In addition, Eros' inferred composition (an S-class asteroid) and its observed impact crater population suggest that it originated in the asteroid belt and at some time migrated inwards to its current near-Earth orbit, resulting in a two- to four-fold increase in solar insolation. Dynamical simulations indicate such orbit migration can occur in less than 5 Myr, comparable to or less than the thermal diffusion timescale for Eros. In finite element simulations of an Eros-sized ellipsoid using reasonable input parameters, we have found that these stresses can exceed 10 MPa, enough to cause faulting in the already heavily impact-fractured asteroid. Fully 3-D finite element analyses using the measured shape of Eros permit a comparison between predicted stress orientations and the observed lineations on Eros.
Dombard Andrew J.
Freed Andrew M.
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