(16) Psyche: A mesosiderite-like asteroid?

Matti Viikinkoski (1) , Pierre Vernazza (2) , Josef Hanuš (3) , Hervé Le Coroller (2) , K. Tazhenova (2) , Benoît Carry (4) , Michael Marsset (5) , Alexis Drouard (2) , Franck Marchis (6) , Romain Fetick (2) , Thierry Fusco (2, 7) , Josef Ďurech (3) , Mirel Birlan (8) , Jérôme Berthier (8) , Przemyslław Bartczak (9) , Christophe Dumas (10) , Julie Castillo-Rogez (11) , Fabrice Cipriani (12) , François Colas (8) , Marin Ferrais (13) , J. Grice (14, 4) , Emmanuël Jehin (13) , Laurent Jorda (2) , Mikko Kaasalainen (1) , Agnieszka Kryszczynska (9) , Philippe Lamy (15) , Anna Marciniak (9) , Tadeusz Michalowski (9) , Patrick Michel (4) , M. Pajuelo (8, 16) , Edyta Podlewska-Gaca (9, 17) , Toni Santana-Ros (9) , Paolo Tanga (4) , Frédéric Vachier (8) , Arthur Vigan (2) , Brian Warner (18) , Oliver Witasse (12) , Bin Yang (19)

1 TUT - Tampere University of Technology [Tampere]
2 LAM - Laboratoire d'Astrophysique de Marseille
3 Astronomical Institute of Charles University
4 LAGRANGE - Joseph Louis LAGRANGE
5 ARC - Astrophysics Research Centre [Belfast]
6 SETI - Search for Extraterrestrial Intelligence Institute
7 DOTA, ONERA, Université Paris Saclay (COmUE) [Châtillon]
8 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides
9 Faculty of Physics [Poznań]
10 TMT International Observatory
11 JPL - Jet Propulsion Laboratory
12 ESTEC - European Space Research and Technology Centre
13 Institut d'Astrophysique et de Géophysique [Liège]
14 School of Physical Sciences - Open University
15 LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
16 PUCP - Pontificia Universidad Católica del Perú = Pontifical Catholic University of Peru
17 University of Szczecin
18 CS3 - Center for Solar System Studies
19 ESO - European Southern Observatory [Santiago]

Context. Asteroid (16) Psyche is the target of the NASA Psyche mission. It is considered one of the few main-belt bodies that could be an exposed proto-planetary metallic core and that would thus be related to iron meteorites. Such an association is however challenged by both its near- and mid-infrared spectral properties and the reported estimates of its density. Aims: Here, we aim to refine the density of (16) Psyche to set further constraints on its bulk composition and determine its potential meteoritic analog. Methods: We observed (16) Psyche with ESO VLT/SPHERE/ZIMPOL as part of our large program (ID 199.C-0074). We used the high angular resolution of these observations to refine Psyche's three-dimensional (3D) shape model and subsequently its density when combined with the most recent mass estimates. In addition, we searched for potential companions around the asteroid. Results: We derived a bulk density of 3.99 ± 0.26 g cm-3 for Psyche. While such density is incompatible at the 3-sigma level with any iron meteorites (˜7.8 g cm-3), it appears fully consistent with that of stony-iron meteorites such as mesosiderites (density ˜4.25 g cm-3). In addition, we found no satellite in our images and set an upper limit on the diameter of any non-detected satellite of 1460 ± 200 m at 150 km from Psyche (0.2% × RHill, the Hill radius) and 800 ± 200 m at 2000 km (3% × RHill). Conclusions: Considering that the visible and near-infrared spectral properties of mesosiderites are similar to those of Psyche, there is merit to a long-published initial hypothesis that Psyche could be a plausible candidate parent body for mesosiderites. Based on observations made with 1) ESO Telescopes at the La Silla Paranal Observatory under programs 086.C-0785 (PI Carry) and 199.C-0074 (PI Vernazza); and 2) 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.Tables A1 and A2 and reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/L3

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

Matti Viikinkoski, Pierre Vernazza, Josef Hanuš, Hervé Le Coroller, K. Tazhenova, et al.. (16) Psyche: A mesosiderite-like asteroid?. Astronomy and Astrophysics - A&A, 2018, 619, pp.L3. ⟨10.1051/0004-6361/201834091⟩. ⟨hal-02118100⟩