Rotationally Resolved Mid-infrared Spectroscopy of (16) Psyche

Abstract

Asteroid (16) Psyche is theorized to be an exposed iron core of a primordial asteroid and is the target of the upcoming NASA Psyche mission. Recent observations of Psyche identified the presence of rotational heterogeneity, a fine-grained regolith, pyroxene, and hydrated minerals on its surface. We obtained rotationally resolved mid-infrared (MIR) spectroscopy of Psyche with the Stratospheric Observatory for Infrared Astronomy to explore its compositional heterogeneity and to assess its mineralogy. We used a thermophysical model of Psyche to estimate and remove its thermal flux at the time of observation to obtain emissivity spectra at 14 different epochs in its rotation. We find that the MIR emissivity does not vary significantly over the rotation of the asteroid, though this may be due to similar aspect angles. We find a lack of mineralogical features, which could suggest that materials on Psyche in the region we observed are not infrared active and consistent with a metal or oxide surface. Differences between the presented spectra and previous studies might indicate a hemispherical compositional dichotomy.