安部 正真

Abstract Analyzing primitive extraterrestrial samples from asteroids is key to understanding the evolution of the early solar system. The OSIRIS‐REx mission returned samples from the B‐type asteroid Bennu, providing a valuable opportunity to compare them with the Ryugu samples collected by the Hayabusa2 mission. This study examines the representativeness of a fraction of the Bennu samples, which was allocated from NASA to JAXA, by nondestructive characterization of their physical and spectral properties without atmospheric exposure. The reflectance and observed spectral features in the visible‐to‐infrared range of the Bennu sample resemble those from the spectroscopic analysis of different fractions. Additionally, we found differences in the slope of the visible range and band‐center of ~2.7 μm band between the samples and the asteroid surface, which could be explained by the degree of space weathering. A comparative analysis of the Bennu and Ryugu samples revealed spectral similarities, including absorption features indicative of Mg‐rich phyllosilicates, organics, and carbonates, without any evidence of sampling bias or terrestrial alteration. This finding can be used as a benchmark for subsequent Ryugu–Bennu comparative studies.

リュウグウ試料の分析・研究により，多様な有機物や水，特定の揮発性元素の存在が確認され，太陽系最初期の物質の化学進化の過程，とりわけ有機物や水の起源に関する理解が大きく進展した．一連の研究成果は，チーム内の機器と達成すべき科学目標を中心に研究者同士が有機的に連携することで，極少量の試料からでさえ，多くの科学的知見を得られることを示した．また，試料が地球由来の汚染を受けていない状態で初期記載から実際の分析まで実施できたことは，Ph2KとASRGで培った惑星物質のキュレーション技術全般がもたらした大きな成果である．今後，得られた知見を活かし，惑星物質キュレーションのさらなる高度化を図るとともに，戦略的かつ持続的な惑星物質の分析基盤の構築と人材育成を含む国際的な研究ネットワークの拡充が期待される．