Open Access BASE2019

Homogeneous internal structure of CM-like asteroid (41) Daphne

Carry, B; Vachier, F; Berthier, J; Marsset, M; Vernazza, P; Grice, J; Merline, W. J; Lagadec, E; Fienga, A; Conrad, A; Podlewska-Gaca, E; Santana-Ros, T; Viikinkoski, M; Hanuš, J; Dumas, C; Drummond, J. D; Tamblyn, P. M; Chapman, C. R; Behrend, R; Bernasconi, L; Bartczak, P; Benkhaldoun, Z; Birlan, M; Castillo-Rogez, J; Cipriani, F; Colas, F; Drouard, A; Ďurech, J; Enke, B. L; Fauvaud, S; Ferrais, M; Fetick, R; Fusco, T; Gillon, M; Jehin, E; Jorda, L; Kaasalainen, M; Keppler, M; Kryszczynska, A; Lamy, P; Marchis, F; Marciniak, A; Michalowski, T; Michel, P; Pajuelo, M; Tanga, P; Vigan, A; Warner, B; Witasse, O; Yang, B; Zurlo, A

Open Access

Abstract

Context. CM-like asteroids (Ch and Cgh classes) are a major population within the broader C-complex, encompassing about 10% of the mass of the main asteroid belt. Their internal structure has been predicted to be homogeneous, based on their compositional similarity as inferred from spectroscopy and numerical modeling of their early thermal evolution. Aims. Here we aim to test this hypothesis by deriving the density of the CM-like asteroid (41) Daphne from detailed modeling of its shape and the orbit of its small satellite. Methods. We observed Daphne and its satellite within our imaging survey with the Very Large Telescope extreme adaptive-optics SPHERE/ZIMPOL camera and complemented this data set with earlier Keck/NIRC2 and VLT/NACO observations. We analyzed the dynamics of the satellite with our Genoid meta-heuristic algorithm. Combining our high-angular resolution images with optical lightcurves and stellar occultations, we determine the spin period, orientation, and 3D shape, using our ADAM shape modeling algorithm. Results. The satellite orbits Daphne on an equatorial, quasi-circular, prograde orbit, like the satellites of many other large main-belt asteroids. The shape model of Daphne reveals several large flat areas that could be large impact craters. The mass determined from this orbit combined with the volume computed from the shape model implies a density for Daphne of 1.77 +/- 0.26 g cm(-3) (3 sigma). This density is consistent with a primordial CM-like homogeneous internal structure with some level of macroporosity (approximate to 17%). Conclusions. Based on our analysis of the density of Daphne and 75 other Ch/Cgh-type asteroids gathered from the literature, we conclude that the primordial internal structure of the CM parent bodies was homogeneous. ; ESO programs [281.C-5011, 099.D-0098, 199.C-0074(A)]; W.M. Keck Foundation; Paris Observatory; National Science Foundation; NASA; CNRS/INSU/PNP; Czech Science Foundation [18-09470S]; European Union's Horizon 2020 Research and Innovation Programme [687378]; Belgian Fund for Scientific Research (Fond National de la Recherche Scientifique, FNRS) [FRFC 2.5.594.09]; University of Liege; Canadian Space Agency; National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program [NCC 5-538]; NASA [09-NEOO009-0001]; National Science Foundation [0506716, 0907766] ; Open access journal. ; This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.

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