论文标题
小行星龙古的前星星
Presolar stardust in asteroid Ryugu
论文作者
论文摘要
作为Jaxa Hayabusa2 Mission的一部分，我们在最近从C型小行星Ryugu返回的样品中对基于纳米菌的搜索进行了搜索。我们报告了通常在碳质软管陨石中鉴定出的所有主要前晶类型的所有主要前晶类型：1个硅酸盐，1个氧化物，1个O-动态超新星，含糊不清的相位歧义相，38 SIC，38 SIC和16碳质晶粒。至少两个碳颗粒是前置石墨，而几种具有中等C同位素异常的谷物可能是有机物。前硅酸盐位于碎屑中，岩性变化较小，而典型的岩石基质则变化较少。 The matrix-normalized presolar grain abundances in Ryugu are 4.8$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm for SiC grains and 11$^{+5}_{-3}$ ppm for carbonaceous grains. Ryugu在同位素和岩石学上类似于碳质Ivuna型（CI）软骨。为了比较Ryugu与CI软骨的原位前晶粒丰度，我们还绘制了Ivuna和Orgueil样品，并发现了总共有SIC谷物和6种碳质晶粒。未检测到O-反对晶粒。 CI软骨中的基质拟态化的前粒晶粒丰度与Ryugu中的矩阵相似：23 $^{+7} _ { - 6} $ ppm SIC和9.0 $^{+5.3} _ { - 4.6} $ ppm ppm ppm ppm cpm carbonaceous carbonaceous Grains。因此，我们的结果提供了支持Ryugu-CI连接的进一步证据。他们还揭示了Ryugu样品中的小规模异质性的有趣暗示，例如局部不同的变化程度，可以保留精致的前置材料。
We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are 4.8$^{+4.7}_{-2.6}$ ppm for O-anomalous grains, 25$^{+6}_{-5}$ ppm for SiC grains and 11$^{+5}_{-3}$ ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23 $^{+7}_{-6}$ ppm SiC and 9.0$^{+5.3}_{-4.6}$ ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.
