Asteroid 16 Psyche: Shape, Features, and Global Map
Abstract
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) × 238(−4/+6 km) × 171 km (−1/+5 km), an effective spherical diameter D_(eff) = 222-1/+4 km, and a spin axis (ecliptic lon, lat) of (36°, −8°) ± 2°. 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. (2020).
Additional Information
© 2021. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 January 5; revised 2021 April 22; accepted 2021 April 22; published 2021 July 15. At the time of the 2015 and 2017 radar observations, Arecibo Observatory was operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968) in alliance with Ana G. Méndez-Universidad Metropolitana and Universities Space Research Association. The Arecibo planetary radar system was supported by the National Aeronautics and Space Administration under grant No. NNX12AF24G issued through the Near-Earth Object Observations program. Additional support for radar data analysis and publication is provided by NASA grant No. 80NSSC19K0523. This work made use of the JPL Horizons ephemeris service and NASA's Astrophysics Data System. This paper makes use of the following ALMA data: ADS/JAO.ALMA\#2018.1.01271.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank M. Viikinkoski for providing the optical albedo data used in Figure 10. We also gratefully acknowledge the use of observations made at the ESO Telescopes at the La Silla Paranal Observatory (VLT) under program 199.C-0074 (PI Vernazza). These data are available at http://observations.lam.fr/astero/. We thank A. Conrad, J. Drummond, and W. Merline and gratefully acknowledge the use of observations from the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We thank E. Cloutis for conversations regarding the spectral nature of metallic minerals. We also are grateful to the following for observing the 2019 October 24 stellar occultation by Psyche: D. Palmer, P. Maley, D. Dunham, J. Dunham, T. George, S. Herchak, R. Jones, R. Reaves, D. Stanbridge, W. Thomas, T. Blank, P. Yeargain, and R. Wasson.Attached Files
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Additional details
- Eprint ID
- 110016
- Resolver ID
- CaltechAUTHORS:20210726-213747363
- NSF
- AST-1100968
- NASA
- NNX12AF24G
- NASA
- 80NSSC19K0523
- W. M. Keck Foundation
- Created
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2021-07-26Created from EPrint's datestamp field
- Updated
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2021-07-26Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department