Searching remnants of biomolecules in carbonaceous matter in the oldest sedimentary rocks

2022 Fiscal Year Final Research Report

• Project/Area Number: 18K13651
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17050:Biogeosciences-related
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: IGISU Motoko 国立研究開発法人海洋研究開発機構, 超先鋭研究開発部門(超先鋭研究開発プログラム), 特別研究員(RPD) (00518285)
• Project Period (FY): 2018-04-01 – 2023-03-31
• Keywords: 最古堆積岩 / 炭質物 / STXM-XANES

Outline of Final Research Achievements

Carbonaceous matter (CM) in Archean sedimentary rocks can provide important insights into understanding the biological activity on early Earth, although a biological origin for this material remains debated. Herein, CM from the ~3.95 billion-year-old (Ga) and the ~3.5 Ga sedimentary rocks, was analyzed using carbon X-ray absorption near edge structure (C-XANES) and micro-Raman spectroscopy. The ~3.95 Ga CM is highly graphitized. The ~3.5 Ga CM is mainly composed of disordered aromatic structures, potentially containing minor heteroatoms (hydrogen and possibly oxygen). These characteristics resemble those of some CM from Archean sedimentary rocks, and abiotically synthesized graphite, but differ from those of CM produced via Fischer-Tropsch-type synthesis. However, our observations indicate the observed C-XANES spectra can be explained by either biotically or abiotically produced organic matter at this stage.

Free Research Field

地質学、地球化学

Academic Significance and Societal Importance of the Research Achievements

地球上にはいつから生命が存在したのだろうか。この根源的な問題に実証的解答を与えるには、地質記録から生命の痕跡を探すことが最も直接的な手段となる。本研究では、生体分子に特徴的な化学結合に着目し、堆積岩中に保存される炭質物の起源生物を特定することを大目標とする。そのために、最新の局所分析を太古代初期の堆積岩中の炭質物に適用し、炭質物の化学結合状態を決定することを試みた。