Characterizing the regolith of a broad sample of near-Earth asteroids (NEAs) is necessary to understand their ensemble properties and evolution. Our team combines high-fidelity shape models and near-IR spectroscopic data obtained over multiple viewing geometries and rotational phases with our thermophysical model to describe the global and local properties of NEA surfaces in more detail than possible with simpler approaches. Our technique, which samples both the thermal emission and reflectance, allows for the thermal and scattering properties of different regions on the surface to be investigated, thus enabling a better understanding of the heterogeneity of an object’s surface in addition to its global properties. We present results from our investigation of (433) Eros, a particularly interesting object given the availability of detailed information from the NEAR Shoemaker spacecraft mission.
We obtained near-IR spectra of Eros using the NASA/IRTF SpeX instrument in LXD 1.9 mode (1.9-4.2 μm) over 3 epochs in 2009-2011 and LXD Long modes (1.98-5.3 μm) over 23 epochs 2018-2019. We also analyzed published IRTF SpeX LXD Short data (Rivkin et al 2018) from 6 additional epochs in 2011-2012, and we modeled 3 epochs of published mid-IR 8-13 micron spectra of Eros taken with the Spectrocam-10 on the 200" Hale telescope of Palomar Observatory in 2002 (Lim et al 2005). These 35 spectra probe a variety of rotation phases and illumination geometries, which allows us to constrain Eros’s properties at the hemispherical, and in one case sub-hemispherical, level. The shape, topography, and albedo properties revealed by NEAR allow us to connect our thermal spectra to the thermal properties of specific locations, as well as to constrain the global- average thermal properties. We will show results from our thermophysical modeling of Eros using our code SHERMAN (Magri et al. 2018, Icarus 303, 203-219) and will discuss how Eros’s thermal emission varies over the surface and what that implies for the heterogeneity of Eros’s surface properties. Previous ground-based thermal observations of Eros examined a limited number of rotational phases; this work combines some of those data with our new dataset to produce a rotationally-resolved model of Eros’s surface.