小惑星ベンヌの起源は、生命に必要な成分を含む、はるか昔に失われた塩の世界だった(Asteroid Bennu comes from a long-lost salty world with ingredients for life)

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2025-01-29 アリゾナ大学

NASAのOSIRIS-RExミッションによって回収された小惑星ベンヌのサンプルを分析した結果、生命の基本構成要素であるアミノ酸やDNA・RNAの塩基が含まれていることが明らかになりました。 これらの有機分子は、ベンヌの親天体であった大型小惑星内の塩水環境で形成されたと考えられています。この発見は、初期の太陽系において、生命の材料が広く存在していた可能性を示唆しており、地球上の生命の起源や他の惑星での生命の可能性に関する理解を深めるものです。

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小惑星(101955)ベンヌのサンプルに含まれる豊富なアンモニアと窒素を多く含む可溶性有機物 Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu

Daniel P. Glavin,Jason P. Dworkin,Conel M. O’D. Alexander,José C. Aponte,Allison A. Baczynski,Jessica J. Barnes,Hans A. Bechtel,Eve L. Berger,Aaron S. Burton,Paola Caselli,Angela H. Chung,Simon J. Clemett,George D. Cody,Gerardo Dominguez,Jamie E. Elsila,Kendra K. Farnsworth,Dionysis I. Foustoukos,Katherine H. Freeman,Yoshihiro Furukawa,Zack Gainsforth,Heather V. Graham,Tommaso Grassi,Barbara Michela Giuliano,Victoria E. Hamilton,… Dante S. Lauretta
Nature Astronomy  Published:29 January 2025
DOI:https://doi.org/10.1038/s41550-024-02472-9

小惑星ベンヌの起源は、生命に必要な成分を含む、はるか昔に失われた塩の世界だった(Asteroid Bennu comes from a long-lost salty world with ingredients for life)

Abstract

Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from the B-type asteroid Bennu by the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer mission enabled us to study pristine carbonaceous astromaterial without uncontrolled exposure to Earth’s biosphere. Here we show that Bennu samples are volatile rich, with more carbon, nitrogen and ammonia than samples from asteroid Ryugu and most meteorites. Nitrogen-15 isotopic enrichments indicate that ammonia and other N-containing soluble molecules formed in a cold molecular cloud or the outer protoplanetary disk. We detected amino acids (including 14 of the 20 used in terrestrial biology), amines, formaldehyde, carboxylic acids, polycyclic aromatic hydrocarbons and N-heterocycles (including all five nucleobases found in DNA and RNA), along with ~10,000 N-bearing chemical species. All chiral non-protein amino acids were racemic or nearly so, implying that terrestrial life’s left-handed chirality may not be due to bias in prebiotic molecules delivered by impacts. The relative abundances of amino acids and other soluble organics suggest formation and alteration by low-temperature reactions, possibly in NH3-rich fluids. Bennu’s parent asteroid developed in or accreted ices from a reservoir in the outer Solar System where ammonia ice was stable.

1701物理及び化学
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