We develop a shape model of asteroid 16 Psyche using observations acquired in a wide range of wavelengths:
Arecibo S-band delay-Doppler imaging, Atacama Large Millimeter Array (ALMA) plane-of-sky imaging, adaptive optics (AO) images from Keck and the Very Large Telescope (VLT), and a recent stellar occultation.

Our shape model has dimensions 278 (-4/+8) km x 238 (-4/+6) km x 171 (-1/+5) km, an effective spherical diameter Deff = 222 -1/+4 km, and a spin axis (ecliptic lon, lat) of (36 deg, -8 deg) +/- 2 deg. We survey all the features previously reported to exist, tentatively identify several new features, and produce a global map of Psyche. Using 30 calibrated radar echoes, we find Psyche’s overall radar albedo to be 0.34 +/- 0.08 suggesting that the upper meter of regolith has a significant metal (i.e., Fe-Ni) content. We find four regions of enhanced or complex radar albedo, one of which correlates well with a previously identified feature on Psyche, and all of which appear to correlate with patches of relatively high optical albedo.

Based on these findings, we cannot rule out a model of Psyche as a remnant core, but our preferred interpretation is that Psyche is a differentiated world with a regolith composition analogous to enstatite or CH/CB chondrites and peppered with localized regions of high metal concentrations. The most credible formation mechanism for these regions is ferrovolcanism as proposed by Johnson et al. (Nature Astronomy vol 4, January 2020, 41-44).

Michael K. Shepard, Katherine de Kleer, Saverio Cambioni, Patrick A. Taylor, Anne K. Virkki, Edgard G. Rivera-Valentin, Carolina Rodriguez Sanchez-Vahamonde, Luisa Fernanda Zambrano-Marin, Christopher Magri, David Dunham, John Moore, Maria Camarca

Comments: 45 pages, 10 embedded figures, 6 tables
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: Michael K. Shepard et al 2021 Planet. Sci. J. 2 125
DOI: 10.3847/PSJ/abfdba
Cite as: arXiv:2110.03635 [astro-ph.EP] (or arXiv:2110.03635v1 [astro-ph.EP] for this version)
Submission history
From: Michael Shepard
[v1] Thu, 7 Oct 2021 17:23:13 UTC (1,818 KB)