Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites-猫眼课题宝

DOI：

10.1126/science.abn7850

发表时间：

2022-06

期刊：

Science

影响因子：

56.9

通讯作者：

中科院分区：

综合性期刊1区

文献类型：

作者：

T. Yokoyama;K. Nagashima;I. Nakai;E. Young;Yoshinari Abe;J. Aléon;C. Alexander;S. Amari;Y. Amelin;K. Bajo;M. Bizzarro;A. Bouvier;R. Carlson;M. Chaussidon;B.-G. Choi;N. Dauphas;A. Davis;T. Di Rocco;W. Fujiya;R. Fukai;I. Gautam;M. Haba;Y. Hibiya;H. Hidaka;Hisashi Homma;P. Hoppe;G. Huss;K. Ichida;T. Iizuka;T. Ireland;A. Ishikawa;Motoo Ito;S. Itoh;N. Kawasaki;N. Kita;K. Kitajima;T. Kleine;S. Komatani;A. Krot;Ming‐Chang Liu;Y. Masuda;K. McKeegan;M. Morita;K. Motomura;F. Moynier;A. Nguyen;L. Nittler;M. Onose;A. Pack;Changkun Park;L. Piani;L. Qin;S. Russell;N. Sakamoto;M. Schönbächler;L. Tafla;Haolan Tang;K. Terada;Y. Terada;T. Usui;S. Wada;M. Wadhwa;R. Walker;K. Yamashita;Q. Yin;S. Yoneda;Hiroharu Yui;A. Zhang;H. Connolly;D. Lauretta;Tomoki Nakamura;H. Naraoka;T. Noguchi;R. Okazaki;K. Sakamoto;H. Yabuta;M. Abe;M. Arakawa;A. Fujii;M. Hayakawa;N. Hirata;N. Hirata;R. Honda;C. Honda;S. Hosoda;Y. Iijima;H. Ikeda;M. Ishiguro;Y. Ishihara;T. Iwata;K. Kawahara;S. Kikuchi;K. Kitazato;K. Matsumoto;M. Matsuoka;T. Michikami;Y. Mimasu;A. Miura;T. Morota;S. Nakazawa;N. Namiki;H. Noda;R. Noguchi;N. Ogawa;K. Ogawa;T. Okada;C. Okamoto;G. Ono;M. Ozaki;T. Saiki;N. Sakatani;H. Sawada;H. Senshu;Y. Shimaki;K. Shirai;S. Sugita;Y. Takei;H. Takeuchi;Satoshi Tanaka;E. Tatsumi;F. Terui;Y. Tsuda;R. Tsukizaki;K. Wada;Sei‐ichiro Watanabe;M. Yamada;T. Yamada;Yukio Yamamoto;H. Yano;Y. Yokota;Keisuke Yoshihara;M. Yoshikawa;K. Yoshikawa;S. Furuya;K. Hatakeda;T. Hayashi;Y. Hitomi;K. Kumagai;Akiko Miyazaki;A. Nakato;M. Nishimura;H. Soejima;A. Suzuki;T. Yada;D. Yamamoto;K. Yogata;M. Yoshitake;S. Tachibana;H. Yurimoto

碳质陨石被认为是C型（碳质）小行星的碎片。C型小行星（162173）Ryugu的样本由隼鸟2号航天器取回。我们测量了Ryugu样品的矿物学和大量的化学和同位素组成。这些样品主要由类似于碳质球粒陨石的物质组成，特别是CI（Ivuna型）组。这些样品主要由在母星子上的含水流体中形成的矿物组成。原始矿物在37° ± 10°C的温度下被流体改变，大约在太阳系第一个固体形成后520 - 70 + 80万年（统计）或520 - 21 + 160万年（系统）。在水蚀变之后，Ryugu样品可能从未被加热到约100°C以上。这些样品的化学成分比其他天然样品更接近太阳光球层。隼鸟2号宇宙飞船于2019年在小行星（162173）Ryugu上进行了两次着陆，在此期间收集了表面物质的样本。这些样本于2020年12月被运送到地球。返回样品的颜色、形状和形态与Hayabusa 2在Ryugu上观察到的一致，表明它们是小行星的代表。对样本的实验室分析可以确定Ryugu的化学成分，并提供有关其形成和历史的信息。我们使用实验室分析来告知以下问题：（i）Ryugu的元素丰度是多少？(ii)龙宫的同位素组成是什么？(iii)Ryugu是由形成太阳系的圆盘中产生的主要物质组成，还是由小行星或母小行星上产生的次要物质组成？(iv)龙谷的构成材料是什么时候形成的？(v)龙谷和陨石有什么关系？结果我们定量了Ryugu样品中66种元素的丰度：H、Li、Be、C、O、Na、Mg、Al、Si、P、S、Cl、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Rb、Sr、Y、Zr、Nb、Mo、Ru、Rh、Pd、Ag、Cd、In、Sn、Te、Cs、Ba、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb，Dy、Ho、Er、Tm、Yb、Lu、Hf、Ta、W、Tl、Pb、Bi、Th和U。第一次和第二次着陆地点的样品之间的化学成分略有变化，但这些变化可能是由于所分析的样品之间的异质性造成的。Cr、Ti同位素组成和挥发性元素丰度与CI（Ivuna-like）球粒陨石群中的碳质陨石相似。Ryugu样品由矿物磁铁矿、软锰矿、白云石和磁黄铁矿组成，作为嵌入由蛇纹石和皂石组成的基质中的颗粒。这种矿物组合和结构也与CI陨石相似。无水硅酸盐几乎不存在，这表明材料中存在广泛的液态水-岩石反应（含水蚀变）。我们得出的结论是，样品主要由次生物质形成的母体中的水蚀变，其中Ryugu后来形成。大体积Ryugu样品中的氧同位素也类似于CI陨石。我们用氧同位素测温法测定了白云石和磁铁矿从水溶液中沉淀出来的温度，我们发现这个温度是37° ± 10°C。53 Mn-53 Cr同位素确定了水蚀变的年代为太阳系诞生后520 - 70 + 80万年（统计）或520 - 21 + 160万年（系统）。层状硅酸盐矿物是Ryugu样品中水的主要宿主。Ryugu的结构水的量类似于CI碳酸盐，但Ryugu的层间水基本上不存在，这表明层间水损失到空间中。结构水的丰度和脱水实验的结果表明，从水蚀变到现在，Ryugu样品保持在~100°C以下。我们将层间水的去除归因于冲击加热、太阳能加热、太阳风照射和长期暴露于太空的超真空的组合。层状硅酸盐层间水的损失可能是一些碳质小行星的彗星状活动和小行星Bennu表面固体物质喷射的原因。结论龙谷陨石样品与CI球粒陨石最为相似，但化学成分更为原始。Ryugu样本的化学成分与太阳光球层的化学成分比实验室研究的任何其他天然样本的化学成分更接近。CI陨石似乎在地球上或进入大气层时被修改过。这些矿物的改性包括有机物和层状硅酸盐结构的改变、陆地水的吸附以及硫酸盐和铁矾的形成。这些问题不会影响Ryugu样品。这些修改可能改变了CI陨石的密度、孔隙度和密度，导致CI陨石、隼鸟2号对龙宫表面的测量以及返回地球的龙宫样本之间的差异。Ryugu样品的代表性岩相学，命名为C 0002-C1001。颜色表示由x射线光谱测定的元素丰度。铁、硫和钙的线依次显示为红色、绿色和蓝色（RGB）颜色通道。这些元素的组合被分配给特定的矿物，如图例所示。所有可见的矿物都是在Ryugu母体上通过水蚀变形成的。

Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about 5.2−0.7+0.8 million (statistical) or 5.2−2.1+1.6 million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles that of the Sun’s photosphere than other natural samples do. Description INTRODUCTION The Hayabusa2 spacecraft made two landings on the asteroid (162173) Ryugu in 2019, during which it collected samples of the surface material. Those samples were delivered to Earth in December 2020. The colors, shapes, and morphologies of the returned samples are consistent with those observed on Ryugu by Hayabusa2, indicating that they are representative of the asteroid. Laboratory analysis of the samples can determine the chemical composition of Ryugu and provide information on its formation and history. RATIONALE We used laboratory analysis to inform the following questions: (i) What are the elemental abundances of Ryugu? (ii) What are the isotopic compositions of Ryugu? (iii) Does Ryugu consist of primary materials produced in the disk from which the Solar System formed or of secondary materials produced in the asteroid or on a parent asteroid? (iv) When were Ryugu’s constituent materials formed? (v) What, if any, relationship does Ryugu have with meteorites? RESULTS We quantified the abundances of 66 elements in the Ryugu samples: H, Li, Be, C, O, Na, Mg, Al, Si, P, S, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Tl, Pb, Bi, Th, and U. There is a slight variation in chemical compositions between samples from the first and second touchdown sites, but the variations could be due to heterogeneity among the samples that were analyzed. The Cr-Ti isotopes and abundance of volatile elements are similar to those of carbonaceous meteorites in the CI (Ivuna-like) chondrite group. The Ryugu samples consist of the minerals magnetite, breunnerite, dolomite, and pyrrhotite as grains embedded in a matrix composed of serpentine and saponite. This mineral assemblage and the texture are also similar to those of CI meteorites. Anhydrous silicates are almost absent, which indicates extensive liquid water–rock reactions (aqueous alteration) in the material. We conclude that the samples mainly consist of secondary materials that were formed by aqueous alteration in a parent body, from which Ryugu later formed. The oxygen isotopes in the bulk Ryugu samples are also similar to those in CI chondrites. We used oxygen isotope thermometry to determine the temperature at which the dolomite and magnetite precipitated from an aqueous solution, which we found to be 37° ± 10°C. The 53Mn-53Cr isotopes date the aqueous alteration at 5.2−0.7+0.8 million (statistical) or 5.2−2.1+1.6 million (systematic) years after the birth of the Solar System. Phyllosilicate minerals are the main host of water in the Ryugu samples. The amount of structural water in Ryugu is similar to that in CI chondrites, but interlayer water is largely absent in Ryugu, which suggests a loss of interlayer water to space. The abundance of structural water and results from dehydration experiments indicate that the Ryugu samples remained below ~100°C from the time of aqueous alteration until the present. We ascribe the removal of interlayer water to a combination of impact heating, solar heating, solar wind irradiation, and long-term exposure to the ultrahigh vacuum of space. The loss of interlayer water from phyllosilicates could be responsible for the comet-like activity of some carbonaceous asteroids and the ejection of solid material from the surface of asteroid Bennu. CONCLUSION The Ryugu samples are most similar to CI chondrite meteorites but are more chemically pristine. The chemical composition of the Ryugu samples is a closer match to the Sun’s photosphere than to the composition of any other natural samples studied in laboratories. CI chondrites appear to have been modified on Earth or during atmospheric entry. Such modification of CI chondrites could have included the alteration of the structures of organics and phyllosilicates, the adsorption of terrestrial water, and the formation of sulfates and ferrihydrites. Those issues do not affect the Ryugu samples. Those modifications might have changed the albedo, porosity, and density of the CI chondrites, causing the observed differences between CI meteorites, Hayabusa2 measurements of Ryugu’s surface, and the Ryugu samples returned to Earth. Representative petrography of a Ryugu sample, designated C0002-C1001. Colors indicate elemental abundances determined from x-ray spectroscopy. Lines of iron, sulfur, and calcium are shown as red, green, and blue (RGB) color channels in that order. Combinations of these elements are assigned to specific minerals, as indicated in the legend. All visible minerals were formed by aqueous alteration on Ryugu’s parent body.

Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites

文献摘要

相似文献