Evidence for differentiation of the most primitive small bodies
Evidence for differentiation of the most primitive small bodies
复制标题
最原始小物体分化的证据
DOI：
10.1051/0004-6361/202140342
复制
发表时间：
2021
影响因子：
6.5
通讯作者：
Viikinkoski, M.
中科院分区：
文献类型：
--
作者：
Carry, B.;Vernazza, P.;Vachier, F.;Neveu, M.;Berthier, J.;Hanuš, J.;Ferrais, M.;Jorda, L.;Marsset, M.;Viikinkoski, M.
ContextDynamical 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, comets, and small Kuiper belt objects (KBOs). Indeed, the spectral properties of P- and D-type asteroids resemble that of anhydrous cometary dust.AimsWe aim to gain insights into the above classes of bodies by characterizing the internal structure of a large P- and D-type asteroid.MethodsWe report high-angular-resolution imaging observations of the P-type asteroid (87) Sylvia with the Very Large Telescope Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument. 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 modeled Sylvia’s thermal evolution.ResultsThe 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.ConclusionsSylvia’s low density and differentiated interior can be explained by partial melting and mass redistribution through water percolation. The outer shell should be composed of material similar to interplanetary dust particles (IDPs) and the core should be 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 a 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, must have remained pristine, which is in agreement with in situ observations of these bodies. NASA Lucy mission target (617) Patroclus (diameter ≈140 km) may, however, be differentiated.
DOI：
10.1017/s1539299600010157
发表时间：
1992
期刊：
Highlights of Astronomy
影响因子：
--
作者：
J. Rahe
通讯作者：
J. Rahe
小行星光度目录 V1.1
DOI：
--
发表时间：
2011
期刊：
影响因子：
--
作者：
C. Lagerkvist;P. Magnusson
通讯作者：
P. Magnusson
DOI：
10.1017/9781316339794
发表时间：
2017
期刊：
Japan Geoscience Union
影响因子：
--
作者：
L. Elkins‐Tanton;B. Weiss
通讯作者：
B. Weiss