<p>NASA’s OSIRIS-REx mission returned material from the carbonaceous asteroid Bennu, which is dominated by aqueous-alteration products but preserves rare high-temperature components. Here we present an integrated petrographic, oxygen-isotopic and <sup>26</sup>Al–<sup>26</sup>Mg chronological characterization of refractory inclusions in Bennu samples. All identified inclusions are small (&lt;~100 µm) and commonly preserve mineralogical evidence of in situ aqueous alteration, indicating incorporation into Bennu’s parent body prior to hydration. Their mineralogical characteristics and oxygen-isotopic and <sup>26</sup>Al–<sup>26</sup>Mg systematics demonstrate formation during the earliest stage of Solar System evolution and genetic affinity with refractory inclusions in asteroid Ryugu samples and chondritic meteorites. The shared refractory-inclusion signatures across diverse chondritic materials are consistent with widespread outward transport and mixing of early-formed inner-disk solids. In Bennu samples analyzed thus far, large (&gt;submillimeter) refractory inclusions are absent, in contrast to most carbonaceous chondrites. This size distribution implies that Bennu’s constituents accreted in the outer Solar System beyond the pressure bump associated with proto-Jupiter, which effectively filtered distinct dust populations.</p>

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Refractory inclusions in Bennu samples indicative of outer Solar System accretion

  • Noriyuki Kawasaki,
  • Toru Matsumoto,
  • Sota Arakawa,
  • Naoya Sakamoto,
  • Ken-ichi Bajo,
  • Sara S. Russell,
  • Jessica J. Barnes,
  • Ann N. Nguyen,
  • Timothy J. McCoy,
  • Pierre Haenecour,
  • Hisayoshi Yurimoto,
  • Harold C. Connolly Jr.,
  • Dante S. Lauretta

摘要

NASA’s OSIRIS-REx mission returned material from the carbonaceous asteroid Bennu, which is dominated by aqueous-alteration products but preserves rare high-temperature components. Here we present an integrated petrographic, oxygen-isotopic and 26Al–26Mg chronological characterization of refractory inclusions in Bennu samples. All identified inclusions are small (<~100 µm) and commonly preserve mineralogical evidence of in situ aqueous alteration, indicating incorporation into Bennu’s parent body prior to hydration. Their mineralogical characteristics and oxygen-isotopic and 26Al–26Mg systematics demonstrate formation during the earliest stage of Solar System evolution and genetic affinity with refractory inclusions in asteroid Ryugu samples and chondritic meteorites. The shared refractory-inclusion signatures across diverse chondritic materials are consistent with widespread outward transport and mixing of early-formed inner-disk solids. In Bennu samples analyzed thus far, large (>submillimeter) refractory inclusions are absent, in contrast to most carbonaceous chondrites. This size distribution implies that Bennu’s constituents accreted in the outer Solar System beyond the pressure bump associated with proto-Jupiter, which effectively filtered distinct dust populations.