Saverio Cambioni¹, Katherine de Kleer², Michael Shepard³
Journal of Geophysical Research (Planets) (in Press) Link to Article [https://doi.org/10.1029/2021JE007091]
¹Department of Planetology, Kobe University, Kobe, Department of Earth, Atmospheric & Planetary Sciences, Massachusetts Institute of Technology, 3Cambridge, MA, USA
²Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
³Department of Environmental, Geographical & Geological Sciences, Bloomsburg University, Bloomsburg, PA, USA
Published by arrangement with John Wiley & Sons

Main-belt asteroid (16) Psyche is the largest M-type asteroid, a class of object classically thought to be the metal cores of differentiated planetesimals and the parent bodies of the iron meteorites. de Kleer, Cambioni, and Shepard (2021) presented new data from the Atacama Large Millimiter Array (ALMA), from which they derived a global best-fit thermal inertia and dielectric constant for Psyche, proxies for regolith particle size, porosity, and/or metal content, and observed thermal anomalies that could not be explained by surface albedo variations only. Motivated by this, here we fit a model to the same ALMA dataset that allows dielectric constant and thermal inertia to vary across the surface. We find that Psyche has a heterogeneous surface in both dielectric constant and thermal inertia but, intriguingly, we do not observe a direct correlation between these two properties over the surface. We explain the heterogeneity in dielectric constant as being due to variations in the relative abundance of metal and silicates. Furthermore, we observe that the lowlands of a large depression in Psyche’s shape have distinctly lower thermal inertia than the surrounding highlands. We propose that the latter could be explained by a thin mantle of fine regolith, fractured bedrock, and/or implanted silicate-rich materials covering an otherwise metal-rich surface. All these scenarios are indicative of a collisionally evolved world.