The origin of life remains one of the most fascinating scientific mysteries. Current mainstream theories suggest that life emerged in Earth's early history through a series of spontaneous chemical reactions.
This process likely began with inorganic molecules forming simple organic compounds like amino acids, lipids, and sugars.
These small organic molecules then combined to create larger organic compounds, which eventually assembled into the first primitive life forms. A critical step in this progression—the spontaneous formation of organic molecules from inorganic substances—was famously validated in the Miller-Urey experiment.
Deep-Sea Hydrothermal Vents: The Birthplace of Life?
Most scientists believe these chemical reactions took place near deep-sea hydrothermal systems, often called "black smokers" or "white smokers." These systems, found along oceanic ridges, are the result of geological activity where mineral-rich, superheated water emerges from volcanic fissures and meets the cold seawater, creating dramatic mineral plumes. The expelled fluids contain sulfur and other chemicals that could provide the materials and energy required for early life-forming reactions. This makes hydrothermal vents one of the most plausible environments for the origin of life, offering conditions similar to those of early Earth.
Uncovering the Transition from Inorganic to Organic
While hydrothermal systems are widely regarded as potential cradles of life, how exactly inorganic molecules transformed into organic ones in such an environment remains unclear. A recent breakthrough came when researchers discovered micron-sized, non-biological organic materials within the lithospheric crust of the Southwest Indian Ridge. This finding offers fresh insights into how inorganic substances might have given rise to organic compounds.
Distinguishing Biological and Non-Biological Origins
Non-biological organic matter refers to compounds formed without the involvement of living organisms, typically through high-temperature and high-pressure chemical reactions. Because organic matter produced by living organisms is ubiquitous on Earth, distinguishing non-biological organic matter is a crucial but challenging task.
To address this, researchers analyzed basalt samples collected by the manned submersible Deep Sea Warrior during the TS-10 expedition. Deep-sea environments are ideal for such studies due to their resemblance to Earth's early conditions and their relative isolation from modern biological contamination.
By examining functional groups—reactive clusters of atoms within molecules—in these samples, scientists confirmed that the organic matter was not a product of biological processes. Functional groups play vital roles in determining molecular behavior and interactions, enabling the complex biochemical reactions essential for life. By identifying these chemical markers, researchers could pinpoint the non-biological origins of the organic compounds.
Formation Process: The Role of Goethite
After ruling out biological origins, the focus shifted to understanding how these organic compounds formed. Using advanced analytical techniques, including electron microscopy, time-of-flight secondary ion mass spectrometry, and photothermal infrared nanospectroscopy, alongside density functional theory (DFT) calculations, scientists discovered a close spatial correlation between the organic matter and goethite, a water-rock reaction product.
Goethite's iron atoms can adsorb carbon dioxide, and the surrounding hydroxyl groups (-OH) facilitate hydrogenation reactions, activating the carbon dioxide. This activation allows carbon chains to elongate, leading to the formation of the organic compounds observed. In essence, the goethite acts as a natural catalyst, transforming inorganic molecules into organic precursors.
A Recipe Without a Chef
By combining high-precision microanalysis with computational modeling, researchers have reconstructed how the "kitchen" of deep-sea hydrothermal systems can produce "dishes" of organic matter without the presence of a "chef" (biological organisms). This study not only illuminates the origin of life on Earth but also provides a template for searching for life on other planets and celestial bodies.
Implications for Astrobiology
This discovery offers valuable clues for identifying life beyond Earth. By understanding how organic matter can form in the absence of life, scientists now have a new framework for exploring extraterrestrial environments. It opens the door to unraveling the universal principles behind life's emergence.
Collaborative Efforts
This groundbreaking research was conducted by Dr. Nan Jingbo of the Nanjing Institute of Geology and Paleontology, Dr. Peng Xiaotong of the Institute of Deep-Sea Science and Engineering, and collaborators from Utrecht University in the Netherlands. It was supported by China’s National Key Research and Development Program, the National Natural Science Foundation, the European Research Council, and the Netherlands Organization for Scientific Research (NWO). This interdisciplinary effort bridges Earth's past and the universe's mysteries, bringing humanity closer to answering one of the most profound questions of existence.
