2024

IDSSE researchers make advances on abiotic organic synthesis in nature

Oct 23,2024

In 2024, a research team led by Dr. Xiaotong Peng reported the discovery of abiotic organic compounds in basalt from the oceanic crust of the Southwest Indian Ridge and proposed a novel molecular mechanism for its condensation.

This breakthrough followed the team’s discovery of nanoscale abiotic organic matter in mantle rocks from the Yap Trench in 2021. It represents a significant advance in research on deep-sea carbon cycling and the origin of life, because it sheds light on new pathways for abiotic organic synthesis in nature.

The scientists published their findings in the Proceedings of the National Academy of Sciences (PNAS). Dr. Jingbo Nan from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) is the first author of the paper. Dr. Xiaotong Peng from the Institute of Deep-Sea Science and Engineering of the Chinese Academy of Sciences is the corresponding author.

The origin of life is one of science’s most challenging scientific problems. Deep-sea hydrothermal systems are considered potential sites for the emergence of life and a key focus in the search for extraterrestrial life. This is because these systems provide simple organic material and energy conditions for prebiotic chemical reactions on early Earth, driving the formation of small organic molecules under non-enzymatic, abiotic catalysis.

Now, mineral-catalyzed organic polymerization reactions lay the foundation to produce more complex organic compounds, facilitating evolution from simple organic compounds to intricate functional structures, and eventually to the emergence of life forms.

Fig. 1 The human-occupied vehicle (HOV) Shen Hai Yong Shi (Image by NIGPAS)

Through analysis of sea-floor basalt samples of volcanic origin collected using the human-occupied vehicle (HOV) Shen Hai Yong Shi (TS-10 expedition), Dr. Nan and his colleagues have reported the previously unknown presence of abiotic organic matter. In the upper oceanic crust of the Southwest Indian Ridge, this organic matter occurs as micron-size particles associated with iron oxide and oxyhydroxide minerals (such as goethite), which points to reaction products from water-rock interactions (Fig. 2).

Fig. 2 Scanning electron microscope (SEM) image of micron-scale abiotic organic matter and surrounding goethite in the oceanic crust of the Southwest Indian Ridge. (Image by NIGPAS)

By using correlated in situ microanalysis techniques, including electron microscopy, time-of-flight secondary ion mass spectrometry, and photo-induced force microscopy coupled with nano-infrared spectroscopy, the researchers comprehensively confirmed the absence of characteristic biological molecules and functional groups in the studied carbonaceous matter (Fig. 3), thereby revealing its abiotic origin.

Fig. 3 Multimodal in situ microanalysis techniques reveal the absence of characteristic biomolecular functional groups in the condensed carbonaceous matter (CCM). (Image by NIGPAS)

Based on this, the research team employed density functional theory (DFT) calculations to propose a crucial role of goethite in the molecular-scale catalytic synthesis of abiotic carbonaceous matter (Fig. 4). In this process, hydrogen from hydrothermal fluids participates in a catalytic cycle on the surface of goethite, playing a key role in the initial activation of carbon dioxide and carbon chain (C-C) growth during organic condensation.

Fig. 4 Density functional theory (DFT) calculations reveal the reaction pathways of CO₂ hydrogenation and C-C chain growth on the (001) surface of goethite. (Image by NIGPAS)

This pioneering study integrates multimodal in situ microanalysis with DFT calculations to explore natural abiotic organic synthesis, providing a deep understanding of the formation mechanisms of abiotic carbonaceous matter in mid-ocean ridges, which serve as critical natural laboratories.

This research not only establishes a foundation for understanding mineral-mediated natural organic catalytic reactions but also provides an important reference for identifying abiotic organic matter in hydrothermal systems on other rocky planets.


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