The asteroid (162173) Ryugu and other rubble-pile asteroids are likely re-accumulated fragments of much larger parent bodies that were disrupted by impacts. However, the collisional and orbital pathways from the original parent bodies to subkilometre rubble-pile asteroids are not yet well understood^1,2,3. Here we use Hayabusa2 observations to show that some of the bright boulders on the dark, carbonaceous (C-type) asteroid Ryugu⁴ are remnants of an impactor with a different composition as well as an anomalous portion of its parent body. The bright boulders on Ryugu can be classified into two spectral groups: most are featureless and similar to Ryugu’s average spectrum^4,5, while others show distinct compositional signatures consistent with ordinary chondrites—a class of meteorites that originate from anhydrous silicate-rich asteroids⁶. The observed anhydrous silicate-like material is likely the result of collisional mixing between Ryugu’s parent body and one or multiple anhydrous silicate-rich asteroid(s) before and during Ryugu’s formation. In addition, the bright boulders with featureless spectra and less ultraviolet upturn are consistent with thermal metamorphism of carbonaceous meteorites^7,8. They might sample different thermal-metamorphosed regions, which the returned sample will allow us to verify. Hence, the bright boulders on Ryugu provide new insights into the collisional evolution and accumulation of subkilometre rubble-pile asteroids.

小行星（162173）Ryugu和其他碎石堆小行星可能是更大的母体重新积累的碎片，这些碎片被撞击破坏了。然而，从原始的母体到亚千米碎石堆小行星的碰撞和轨道路径尚未被很好地理解^1,2,3。在这里，我们使用Hayabusa2的观察结果来证明，深色的碳质（C型）小行星Ryugu ⁴上的一些明亮巨石是撞击器的残余物，具有不同的组成以及其母体的异常部分。Ryugu上的明亮巨石可以分为两个光谱组：大多数无特征，与Ryugu的平均光谱相似^4,5，而其他的则显示出与普通球粒陨石一致的独特组成特征-一种来自富含无水硅酸盐的小行星⁶的陨石。观察到的无水硅酸盐样物质很可能是龙古的母体与龙古形成前和形成过程中一种或多种富含无水硅酸盐的小行星之间碰撞混合的结果。此外，明亮的巨石具有无特征的光谱和较少的紫外线上升与碳质陨石^7,8的热变质相一致。他们可能会采样不同的热变形区域，返回的样本将使我们能够对其进行验证。因此，Ryugu上的明亮巨石为亚千米级碎石堆小行星的碰撞演化和积累提供了新的见识。