Review of Jupiter-Trojan asteroids research
-
摘要: 木星特洛伊小行星(Jupiter-Trojan asteroids)是位于木星稳定拉格朗日点上与木星以相同周期围绕太阳稳定运行的小天体. 木星特洛伊小行星作为行星形成过程的活化石记录了行星起源、类地行星有机物与挥发物来源及行星系统整体演化的独特信息. 迄今仅通过地基望远镜或空间望远镜对它们进行过远距离光谱观测,它们仍是太阳系最神秘的天体群之一. 在物质成分上,细粒硅酸盐被认为是构成特洛伊小行星的重要物质. 过去认为特洛伊小行星形成在5 AU附近,新的动力学模型认为特洛伊小行星来自柯伊伯带. NASA的“露西”小行星探测任务(Lucy )将首次近距离探索这些神秘的小天体,有望为解开特洛伊小行星的身世之谜提供重要证据. 本文梳理了木星特洛伊小行星的观测历史、物理性质、光谱性质、物质组成以及形成和演化,并介绍了“露西”的探测任务与目标,为未来我国深空探测计划中的小行星探测提供支撑.Abstract: Jupiter-Trojan asteroids, as fossils of planet formation, orbiting the Sun in Jupiter's stable Lagrange points, provide a unique and critical insight into planetary origins, the sources of volatiles and organics on the terrestrial planets, and the evolution of the planetary system as a whole. To present, Jupiter-Trojan asteroids have only been observed through remote spectroscopic measurements using ground-based telescopes or space telescopes, and they remain one of the most enigmatic groups of celestial bodies. In the past decade, significant advances in understanding their physical and spectral properties have been made, and there has been a revolution in thinking about the origin and evolution of Trojans. Fine-grained silicates that appear to be similar to cometary silicates have gradually replaced water ice and organics as a significant component of the surface composition of Trojan asteroids, and a color bimodality may indicate distinct compositional groups among the Trojans. Whereas Trojans had traditionally been thought to have formed near 5 AU, a new paradigm in which the Trojans formed in the proto-Kuiper Belt, were scattered inward, and then captured in the Trojan swarms as a result of resonant interactions of the giant planets has developed. There are significant differences between the currently determined physical properties of Trojans and Kuiper Belt objects. These differences may be indicative of surface modification attributable to the inward migration of the objects that became the Trojans. The upcoming Lucy mission will provide a unique opportunity to conduct close-up exploration of these enigmatic small celestial bodies, potentially yielding evidence important for unraveling the mysteries surrounding the origin and evolution of Jupiter-Trojan asteroids. This paper provides a comprehensive overview of the observational history, physical and spectral properties, material composition, and formation and evolution of Jupiter-Trojan asteroids, as well as an introduction to the goals and objectives of the Lucy mission. This study provides support for potential future deep space exploration missions that may have the capacity of exploring asteroids.
-
Key words:
- Jupiter-Trojan asteroids /
- spectroscopy /
- composition /
- formation /
- evolution
-
图 1 内太阳系小行星分布示意图(蓝线为行星轨道,绿色为木星特洛伊小行星,白色为主带小行星,橘色为希尔达小行星)(修改自维基百科)
Figure 1. Distribution of internal solar system minor planets (The blue lines are the planet orbits, the green dots are the Jupiter-Trojan asteroids, the white dots are main-belt asteroids, and the orange dots are Hildas) (Credit: "InnerSolarSystem-en" by Mdf at English Wikipedia-Transferred from en.wikipedia to Commons. Licensed under Public Domain via Commons)
图 2 两个光谱组的可见光和近红外平均光谱曲线(修改自Emery et al., 2010)
Figure 2. Combined visible and near infrared average spectra of the two spectral groups (modified from Emery et al., 2010; Credit: AAS. Reproduced with permission)
表 1 露西探测任务飞掠时间表
Table 1. Lucy mission flight time
位置 小行星 光谱类型 飞越时间 主小行星带 (52246) Donaldjohanson C 2025-04-25 特洛伊小行星L4群 (3548) Eurybates
卫星 QuetaC 2027-08-12 (15094) Polymele P 2027-09-15 (11351) Leucus D 2028-04-18 (21900) Orus D 2028-11-11 特洛伊小行星L5群 (617) Patroclus
双星系统P 2033-03-03 -
[1] Alexandersen M, Gladman B, Greenstreet S, et al. 2013. A Uranian Trojan and the frequency of temporary giant-planet co-orbitals[J]. Science, 341(6149): 994-997. doi: 10.1126/science.1238072 [2] Barucci M A, Merlin F, Dotto E, et al. 2006. TNO surface ices-observations of the TNO 55638 (2002 VE) and analysis of the population's spectral properties[J]. Astronomy & Astrophysics, 455(2): 725-730. [3] Bendjoya P, Cellino A, Di Martino M, et al. 2004. Spectroscopic observations of Jupiter Trojans[J]. Icarus, 168(2): 374-384. doi: 10.1016/j.icarus.2003.12.004 [4] Brown M E. 2016. The 3-4 μm spectra of Jupiter Trojan asteroids[J]. The Astronomical Journal, 152(6): 159. doi: 10.3847/0004-6256/152/6/159 [5] Bus S J, Binzel R P. 2002. Phase II of the small main-belt asteroid spectroscopic survey: A feature-based taxonomy[J]. Icarus, 158(1): 146-177. doi: 10.1006/icar.2002.6856 [6] Chapman C R, Gaffey M J. 1979. Reflectance Spectra for 277 Asteroids[M]//Gehrels T. Asteroids. Tucson: University of Arizona Press, 655-687 [7] Connors M, Wiegert P, Veillet C. 2011. Earth’s Trojan asteroid[J]. Nature, 475(7357): 481-483. doi: 10.1038/nature10233. PMID: 21796207. [8] Cruikshank D P. 1977. Radii and albedos of four Trojan asteroids and Jovian satellites 6 and 7[J]. Icarus, 30(1): 224-230. doi: 10.1016/0019-1035(77)90136-1 [9] Cruikshank D P, Roush T L, Bartholomew M J, et al. 1998. The composition of centaur 5145 Pholus[J]. Icarus, 135(2): 389-407. doi: 10.1006/icar.1998.5997 [10] Cruikshank D P, Dalle Ore C M, Roush T L, et al. 2001. Constraints on the composition of Trojan asteroid 624 Hektor[J]. Icarus, 153(2): 348-360. doi: 10.1006/icar.2001.6703 [11] Dahlgren M, Lagerkvist C I, 1995. A study of Hilda asteroids. I. CCD spectroscopy of Hilda asteroids[J]. Astronomy and Astrophysics, 302: 907–914. [12] Dahlgren M, Lagerkvist C I, Fitzsimmons A, et al. 1997. A study of Hilda asteroids. II. Compositional implications from optical spectroscopy[J]. Astronomy and Astrophysics, 323: 606-619. [13] Dalle Ore C M, Dalle Ore L V, Roush T L, et al. 2013. A compositional interpretation of trans-neptunian objects taxonomies[J]. Icarus, 222(1): 307-322. doi: 10.1016/j.icarus.2012.11.015 [14] Dalle Ore C M, Barucci M A, Emery J P, et al. 2015. The composition of “ultra-red” TNOS and Centaurs[J]. Icarus, 252: 311-326. doi: 10.1016/j.icarus.2015.01.014 [15] de La Fuente Marcos C, de La Fuente Marcos R. 2013. Three new stable L5 Mars trojans[J]. Monthly Notices of the Royal Astronomical Society: Letters, 432(1): L31-L35. doi: 10.1093/mnrasl/slt028 [16] Descamps P. 2015. Dumb-bell-shaped equilibrium figures for fiducial contact-binary asteroids and EKBOs[J]. Icarus, 245: 64-79. doi: 10.1016/j.icarus.2014.08.002 [17] Dotto E, Emery J P , Barucci M A, et al. 2008. De Troianis: The Trojans in the Planetary System[M]//Barucci M A. The Solar System Beyond Neptune. Tucson: University of Arizona Press, 383-395 [18] Dumas C, Owen T, Barucci M A. 1998. Near-infrared spectroscopy of low-albedo surfaces of the solar system: Search for the spectral signature of dark material[J]. Icarus, 133(2): 221-232. doi: 10.1006/icar.1998.5927 [19] Dunlap J L, Gehrels T. 1969. Minor planets. III. Lightcurves of a Trojan asteroid[J]. The Astronomical Journal, 74: 796. doi: 10.1086/110860 [20] Emery J P, Brown R H. 2003. Constraints on the surface composition of Trojan asteroids from near-infrared (0.8-4.0 μm) spectroscopy[J]. Icarus, 164(1): 104-121. doi: 10.1016/S0019-1035(03)00143-X [21] Emery J P, Brown R H. 2004. The surface composition of Trojan asteroids: Constraints set by scattering theory[J]. Icarus, 170(1): 131-152. doi: 10.1016/j.icarus.2004.02.004 [22] Emery J P, Cruikshank D P, Van Cleve J. 2006. Thermal emission spectroscopy (5.2-38 μm) of three Trojan asteroids with the Spitzer Space Telescope: Detection of fine-grained silicates[J]. Icarus, 182(2): 496-512. doi: 10.1016/j.icarus.2006.01.011 [23] Emery J P, Dalle Ore C M, Cruikshank D P, et al. 2007. Ices on (90377) Sedna: confirmation and compositional constraints[J]. Astronomy & Astrophysics, 466(1): 395-398. [24] Emery J P, Burr D M, Cruikshank D P. 2010. Near-infrared spectroscopy of Trojan asteroids: Evidence for two compositional groups[J]. The Astronomical Journal, 141(1): 25. [25] Emery J P, Marzari F, Morbidelli A, et al. 2015. The Complex History of Trojan Asteroids[M]//Michel P, Demeo F E, Bottke W F. Asteroids IV. Tucson: University of Arizona Press, 203-220 [26] Fernández Y R, Sheppard S S, Jewitt D C. 2003. The albedo distribution of Jovian Trojan asteroids[J]. The Astronomical Journal, 126(3): 1563. doi: 10.1086/377015 [27] Fernández Y R, Jewitt D, Ziffer J E. 2009. Albedos of small Jovian Trojans[J]. The Astronomical Journal, 138(1): 240. doi: 10.1088/0004-6256/138/1/240 [28] Fleming H J, Hamilton D P. 2000. On the origin of the Trojan asteroids: Effects of Jupiter's mass accretion and radial migration[J]. Icarus, 148(2): 479-493. doi: 10.1006/icar.2000.6523 [29] Fornasier S, Dotto E, Marzari F, et al. 2004. Visible spectroscopic and photometric survey of L5 Trojans: Investigation of dynamical families[J]. Icarus, 172(1): 221-232. doi: 10.1016/j.icarus.2004.06.015 [30] Fornasier S, Dotto E, Hainaut O, et al. 2007. Visible spectroscopic and photometric survey of Jupiter Trojans: Final results on dynamical families[J]. Icarus, 190(2): 622-642. doi: 10.1016/j.icarus.2007.03.033 [31] Gradie J, Veverka J. 1980. The composition of the Trojan asteroids[J]. Nature, 283(5750): 840-842. doi: 10.1038/283840a0 [32] Gradie J, Tedesco E. 1982. Compositional structure of the asteroid belt[J]. Science, 216(4553): 1405-1407. doi: 10.1126/science.216.4553.1405 [33] Grav T, Mainzer A K, Bauer J, et al. 2011. WISE/NEOWISE observations of the Jovian Trojans: Preliminary results[J]. The Astrophysical Journal, 742(1): 40. doi: 10.1088/0004-637X/742/1/40 [34] Grav T, Mainzer A K, Bauer J M, et al. 2012. WISE/NEOWISE observations of the Jovian Trojan population: Taxonomy[J]. The Astrophysical Journal, 759(1): 49. doi: 10.1088/0004-637X/759/1/49 [35] Greenstreet S, Gladman B, Juric M. 2022. Jupiter Trojan temporary interlopers and libration amplitude distributions[C]//AAS/Division for Planetary Sciences Meeting Abstracts. 54(8): 520.02. [36] Hartmann W K, Cruikshank D P. 1978. The nature of Trojan asteroid 624 Hektor[J]. Icarus, 36(3): 353-366. doi: 10.1016/0019-1035(78)90114-8 [37] Hui M T, Wiegert P A, Tholen D J, et al. 2021. The second Earth Trojan 2020 XL5[J]. The Astrophysical Journal Letter, 922: L25. doi: 10.3847/2041-8213/ac37bf [38] Jewitt D C, Luu J X. 1990. CCD spectra of asteroids. II-The Trojans as spectral analogs of cometary nuclei[J]. The Astronomical Journal, 100: 933-944. doi: 10.1086/115572 [39] Jewitt D C, Trujillo C A, Luu J X. 2000. Population and size distribution of small Jovian Trojan asteroids[J]. The Astronomical Journal, 120(2): 1140. doi: 10.1086/301453 [40] Khan M, Witasse O, Martens W, et al. 2022. Design of an in-situ science mission to a Jupiter Trojan[J]. Planetary and Space Science, 225: 105610. [41] Lazzaro D, Angeli C A, Carvano J M, et al. 2004. S3OS2: The visible spectroscopic survey of 820 asteroids[J]. Icarus, 172(1): 179-220. doi: 10.1016/j.icarus.2004.06.006 [42] Levison H F, Marchi S, Noll K, et al. 2021a. NASA's Lucy mission to the Trojan asteroids[C]//2021 IEEE Aerospace Conference (50100). IEEE, 1-10. [43] Levison H F, Olkin C B, Noll K S, et al. 2021b. Lucy mission to the Trojan asteroids: Science goals[J]. The Planetary Science Journal, 2(5): 171. doi: 10.3847/PSJ/abf840 [44] Luu J, Jewitt D, Cloutis E. 1994. Near-infrared spectroscopy of primitive solar system objects[J]. Icarus, 109(1): 133-144. doi: 10.1006/icar.1994.1081 [45] Marchis F, Hestroffer D, Descamps P, et al. 2006. A low density of 0.8 g cm-3 for the Trojan binary asteroid 617 Patroclus[J]. Nature, 439(7076): 565-567. doi: 10.1038/nature04350 [46] Marchis F, Durech J, Castillo-Rogez J, et al. 2014. The puzzling mutual orbit of the binary Trojan asteroid (624) Hektor[J]. The Astrophysical Journal Letters, 783(2): L37. doi: 10.1088/2041-8205/783/2/L37 [47] Marzari F, Scholl H. 1998. The growth of Jupiter and Saturn and the capture of Trojans[J]. Astronomy and Astrophysics, 339: 278-285. [48] Melita M D, Strazzulla G, Bar-Nun A. 2009. Collisions, cosmic radiation, and the colors of the Trojan asteroids[J]. Icarus, 203(1), 134-139. doi: 10.1016/j.icarus.2009.04.024 [49] Merline W J, Weidenschilling S J, Durda D D, et al. 2002. Asteroids Do Have Satellites[M]//Bottke W F. Asteroids III. Tucson: University of Arizona Press, 1: 289-312. [50] Morbidelli A, Levison H F, Tsiganis K, et al. 2005. Chaotic capture of Jupiter's Trojan asteroids in the early solar system[J]. Nature, 435(7041): 462-465. doi: 10.1038/nature03540 [51] Moroz L, Baratta G, Strazzulla G, et al. 2004. Optical alteration of complex organics induced by ion irradiation: 1. Laboratory experiments suggest unusual space weathering trend[J]. Icarus, 170(1): 214-228. doi: 10.1016/j.icarus.2004.02.003 [52] Noll K S. 2005. Solar system binaries[J]. Proceedings of the International Astronomical Union, 1(S229): 301-318. doi: 10.1017/S1743921305006812 [53] Peale S J. 1993. The effect of the nebula on the Trojan precursors[J]. Icarus, 106(1): 308-322. doi: 10.1006/icar.1993.1173 [54] Pitjeva E V, Pitjev N P. 2019. Masses of the Trojan groups of Jupiter[J]. Astronomy Letters, 45(12): 855-860. doi: 10.1134/S1063773719120041 [55] Pollack J B, Hubickyj O, Bodenheimer P, et al. 1996. Formation of the giant planets by concurrent accretion of solids and gas[J]. Icarus, 124(1): 62-85. doi: 10.1006/icar.1996.0190 [56] Sharkey B N L, Reddy V, Sanchez J A, et al. 2019. Compositional constraints for Lucy mission Trojan asteroids via near-infrared spectroscopy[J]. The Astronomical Journal, 158(5): 204. doi: 10.3847/1538-3881/ab46c0 [57] Sheppard S S, Trujillo C. 2006. A survey for Trojan asteroids of Saturn, Uranus and Neptune[C]//AAS/Division for Planetary Sciences Meeting Abstracts#38. 38: 44. [58] Shoemaker E M, Shoemaker C S, Wolfe R F. 1989. Trojan Asteroids: Populations, Dynamical Structure and Origin of the L4 and L5 Swarms[M]//Binzel R P, Gehrels T, Matthew M S. Asteroids II. Tucson: University of Arizona Press, 487-523 [59] Tedesco E F, Noah P V, Noah M, et al. 2002. The supplemental IRAS minor planet survey[J]. The Astronomical Journal, 123(2): 1056. doi: 10.1086/338320 [60] Tenn J S. 1994. Max Wolf: The Twenty-fifth Bruce Medalist[J]. Mercury, 23: 27. [61] Usui F, Kuroda D, Müller T G, et al. 2011. Asteroid catalog using Akari: AKARI/IRC mid-infrared asteroid survey[J]. Publications of the Astronomical Society of Japan, 63(5): 1117-1138. doi: 10.1093/pasj/63.5.1117 [62] Vilas F, Larson S M, Hatch E C, et al. 1993. CCD reflectance spectra of selected asteroids. II. Low-albedo asteroid spectra and data extraction techniques[J]. Icarus, 105(1): 67-78. doi: 10.1006/icar.1993.1111 [63] 王赤, 李晖, 郭孝城, 徐欣峰. 2020. 太阳系边际探测项目的科学问题[J]. 深空探测学报(中英文), 7(6): 517-524. doi: 10.15982/j.issn.2096-9287.2020.20200058.Wang C, Li H, Guo X C, Xu X F. 2020. Scientific objectives for the exploration of the boundary of solar system[J]. Journal of Deep Space Exploration, 7(6): 517-524 (in Chinese). doi: 10.15982/j.issn.2096-9287.2020.20200058. [64] 吴伟仁, 于登云, 黄江川, 等. 2019. 太阳系边际探测研究[J]. 中国科学: 信息科学, 49(1): 1-16Wu W R, Yu D Y, Huang J C, et al. 2019. Exploring the solar system boundary[J]. Scientia Sinica (Informationis), 49(1): 1-16 (in Chinese). [65] 吴伟仁, 王赤, 刘洋, 等. 2023. 深空探测之前沿科学问题探析[J]. 科学通报, 68(6): 606-627Wu W R, Wang C, Liu Y, et al. 2023, Frontier scientific questions in deep space exploration[J]. Chinese Science Bulletin, 68(6): 606-627 (in Chinese). [66] Wyse A B. 1938. The Trojan group[J]. Leaflet of the Astronomical Society of the Pacific, 3: 113. [67] Xu S, Binzel R P, Burbine T H, et al. 1995. Small main-belt asteroid spectroscopic survey: Initial results[J]. Icarus, 115(1): 1-35. doi: 10.1006/icar.1995.1075 [68] Yoshida F, Nakamura T. 2005. Size distribution of faint Jovian L4 Trojan asteroids[J]. The Astronomical Journal, 130(6): 2900. doi: 10.1086/497571 [69] Yoshida F, Nakamura T. 2008. A comparative study of size distributions for small L4 and L5 Jovian Trojans[J]. Publications of the Astronomical Society of Japan, 60(2): 297-301. doi: 10.1093/pasj/60.2.297 [70] 张荣桥, 黄江川, 赫荣伟, 等. 2019. 小行星探测发展综述[J]. 深空探测学报, 6(5): 417-423+455 doi: 10.15982/j.issn.2095-7777.2019.05.002Zhang Q R, Huang J C, He R W, et al. , 2019. The development overview of asteroids exploration[J]. Journal of Deep Space Exploration, 6(5): 417-423+455. (in Chinese). doi: 10.15982/j.issn.2095-7777.2019.05.002 -