Evidence for differentiation of the most primitive small bodies

• Published in: Astronomy & Astrophysics
• Main Authors: Carry, Benoit, Vernazza, P., Vachier, F., Neveu, M., Berthier, J., Hanuš, J., Ferrais, M., Jorda, Laurent, Marsset, M., Viikinkoski, M., Bartczak, P., Behrend, R., Benkhaldoun, Z., Birlan, M, Castillo-Rogez, J., Cipriani, F., Colas, F, Drouard, A., Dudziński, G., P., Desmars, J., Dumas, C., Ďurech, J., Fetick, R., Fusco, T., Grice, J., Jehin, E., Kaasalainen, M., Kryszczynska, A., Lamy, Philippe, Marchis, F., Marciniak, A., Michalowski, T., Michel, P., Pajuelo, M., Podlewska-Gaca, E., Rambaux, N., Santana-Ros, T., Storrs, A., Tanga, P., Vigan, A., Warner, B., Wieczorek, M., Witasse, Olivier, Yang, Bin
• Other Authors: Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS), Institut de Mécanique Céleste et de Calcul des Ephémérides (IMCCE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Lille-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), University of Maryland College Park, University of Maryland System, NASA Goddard Space Flight Center (GSFC), Institute of Astronomy Prague, Univerzita Karlova Praha, Česká republika = Charles University Prague, Czech Republic (UK), Space Sciences, Technologies and Astrophysics Research Institute (STAR), Université de Liège, Department of Earth, Atmospheric and Planetary Sciences MIT, Cambridge (EAPS), Massachusetts Institute of Technology (MIT), Department of Mathematics Tampere, Tampere University of Technology Tampere (TUT), Astronomical Observatory Poznan, Adam Mickiewicz University in Poznań (UAM), Geneva Observatory, Université de Genève = University of Geneva (UNIGE), Oukaimeden Observatory, Université Cadi Ayyad Marrakech (UCA), Astronomical Institute of Romanian Academy, Romanian Academy, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), European Space Research and Technology Centre (ESTEC), Agence Spatiale Européenne = European Space Agency (ESA), Institut Polytechnique des Sciences Avancées (IPSA), Thirty Meter Telescope Observatory, The Open University Milton Keynes (OU), University of Tampere Finland, HELIOS - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), SETI Institute, Pontificia Universidad Católica del Perú = Pontifical Catholic University of Peru (PUCP), Institute of Physics Szczecin, University of Szczecin, Universidad de Alicante, Institut de Ciencies del Cosmos (ICCUB), Universitat de Barcelona (UB), Towson University Towson, MD, United States, Center for Solar System Studies (CS3), European Southern Observatory (ESO)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: Minor planets; asteroids; Sylvia; Kuiper belt; [SDU]Sciences of the Universe [physics]; Jupiter; Tagish; Tagish Lake
• Online Access: https://insu.hal.science/insu-03184663; https://insu.hal.science/insu-03184663v2/document; https://insu.hal.science/insu-03184663v2/file/aa40342-21.pdf; https://doi.org/10.1051/0004-6361/202140342

International audience Dynamical models of Solar System evolution have suggested that the so-called P-and D-type volatile-rich asteroids formed in the outer Solar System beyond Neptune's orbit and may be genetically related to the Jupiter Trojans, the comets and small Kuiper-belt objects (KBOs). Indeed, the spectral properties of P/D-type asteroids resemble that of anhydrous cometary dust. We aim at gaining insights into the above classes of bodies by characterizing the internal structure of a large P/D-type asteroid. Methods. We report high-angular-resolution imaging observations of P-type asteroid (87) Sylvia with VLT/SPHERE. These images were used to reconstruct the 3D shape of Sylvia. Our images together with those obtained in the past with large ground-based telescopes were used to study the dynamics of its two satellites. We also model Sylvia's thermal evolution. The shape of Sylvia appears flattened and elongated (a/b∼1.45 a/c∼1.84). We derive a volume-equivalent diameter of 271 ± 5 km, and a low density of 1378 ± 45 kg•m −3. The two satellites orbit Sylvia on circular, equatorial orbits. The oblateness of Sylvia should imply a detectable nodal precession which contrasts with the fully-Keplerian dynamics of its two satellites. This reveals an inhomogeneous internal structure, suggesting that Sylvia is differentiated. Sylvia's low density and differentiated interior can be explained by partial melting and mass redistribution through water percolation. The outer shell would be composed of material similar to interplanetary dust particles (IDPs) and the core similar to aqueously altered IDPs or carbonaceous chondrite meteorites such as the Tagish Lake meteorite. Numerical simulations of the thermal evolution of Sylvia show that for a body of such size, partial melting was unavoidable due to the decay of long-lived radionuclides. In addition, we show that bodies as small as 130-150 km in diameter should have followed a similar thermal evolution, while smaller objects, such as comets and the KBO Arrokoth, ...