A preliminary analysis of seismological techniques to study Eros and other asteroids

The NEAR Shoemaker mission to near-Earth asteroid 433 Eros provided a great deal of information about the asteroid. Still to be learned are the interior structure and material properties: the local density, strength, and cohesiveness within Eros. Seismology is a way to determine such information. This paper numerically explores performing a seismological experiment on Eros, using an explosive as a seismic source. Computations with the explosive source were performed in an Eulerian hydrocode (CTH) and then results of those computations were transferred to a Lagrangian wavecode (LS-DYNA) to calculate the subsequent seismic wave propagation in the body. To verify the technique, computations were first carried out for two cases where analytical results are known: a uniaxial-strain bar and a sphere. Computations were then performed for a three-dimensional solid model of Eros with surface shape based on NEAR data. Initial computations assumed Eros was isotropic and homogeneous in its material properties. Modal frequency computations for the isotropic, homogeneous Eros were then compared with a model of Eros that included an interior fracture plane. Differences in seismic traces and in modal frequencies show that seismology can differentiate the interior of Eros in particular and other asteroids in general.