2 atmosphere with significant methane and ammonia. This atmosphere rapidly cools (in less than 1,000 years), undergoing photochemical reactions that lead to the formation of a haze rich in tholin, depositing complex nitrogen-rich organic compounds. These organic substances gradually sink and undergo graphitization through interactions with magma. As the hydrogen gas (H2) escapes into space, the atmosphere returns to a neutral state. Eventually, the magmatic gases react with the graphite, resulting in the production of high quantities of clean HCN, HC3N, and isonitriles. Credit: Oliver Shorttle”>
A diagram illustrating the proposed sequence for the efficient production of prebiotic raw materials. The sequence progresses clockwise from the top left corner: Initially, the Earth possesses a neutral atmosphere. This state transitions to a reducing environment after a massive collision at 4.3 billion years ago, converting the impactor’s metallic core to generate a substantial H2-rich atmosphere containing methane and ammonia. Subsequently, this atmosphere swiftly cools (within <1 kyr>) due to the loss of H2, returning the atmosphere to a neutral state. Finally, interactions between magmatic gases and graphite lead to the scrubbing process, yielding significant amounts of pure HCN, HC3N, and isonitriles. Credit: Oliver Shorttle
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Researchers at the University of Cambridge propose that crucial molecules essential for life’s emergence could have originated through a phenomenon known as graphitization. If validated through laboratory experiments, this discovery may enable the recreation of plausible conditions conducive to the beginnings of life.
The question of how the necessary chemicals for life were synthesized has long puzzled scientists. The University of Cambridge researchers have now modeled a scenario where these conditions could naturally occur, producing vital life-building blocks in substantial quantities.
Life’s fundamental components, such as proteins, phospholipids, and nucleotides, rely on molecules containing nitrogen, like nitriles—such as cyanoacetylene (HC3N) and hydrogen cyanide (HCN)—as well as isonitriles like isocyanide (HNC) and methyl isocyanide (CH3NC). While previous studies have hinted at the potential use of these molecules in forming life’s building blocks, the challenge has been to produce them simultaneously in significant amounts within the same environment.
In a recent publication in Life, the researchers demonstrate that the process of graphitization could theoretically yield substantial quantities of these crucial molecules. Experimental verification of this model could indicate that this process played a pivotal role in the early Earth’s transition towards hosting life.
Why is the proposed process more plausible than alternative theories?
Previous models have struggled with the production of various byproducts alongside nitriles, leading to complex chemical systems that impede the formation of life.
Dr. Paul Rimmer, Assistant Professor of Experimental Astrophysics at the Cavendish Laboratory and co-author of the study, emphasizes the importance of simplicity in life’s origins. By controlling the chemistry to favor the exclusive formation of nitriles and isonitriles, graphitization effectively streamlines the chemical environment, promoting the conditions necessary for life to emerge.
Life is not expected to arise in chaotic settings. The unique aspect of graphitization is its ability to purify the environment by selectively generating nitriles and isonitriles, with minimal interference from other reactive compounds.
Initially perceived as a potential obstacle, the selective nature of graphitization ultimately enhances the overall chemical landscape, paving the way for the emergence of life.
This characteristic of graphitization aligns with the simplicity and cleanliness essential for fostering life’s development.
How does the graphitization process function?
During the Hadean eon, a pivotal era in Earth’s history characterized by drastic environmental differences from the present-day Earth, colossal impacts from celestial bodies, possibly as large as planets, were not uncommon. The researchers hypothesize that a significant impact event around 4.3 billion years ago, involving an object comparable in size to the moon, triggered a reaction between the object’s iron content and Earth’s water reserves.
Dr. Oliver Shorttle, Professor of natural philosophy at the Institute of Astronomy and Department of Earth Sciences in Cambridge and co-author of the study, explains that the reaction between the iron and water led to the formation of a tar-like substance on Earth’s surface. This tar subsequently interacted with magma exceeding 1500°C, causing the carbon within the tar to transform into graphite, a stable form of carbon commonly used in pencils.
Following the iron-water reaction, a mist containing reaction products condensed and mingled with the Earth’s crust. Upon exposure to high temperatures, the remaining substances facilitated the production of valuable nitrogen-containing compounds crucial for life’s formation.
What evidence supports this hypothesis?
The theory finds support from the existence of komatiitic rocks, a type of volcanic rock formed under extreme temperatures (>1500°C).
Shorttle highlights the discovery of komatiite rocks in South Africa dating back approximately 3.5 billion years. These rocks, which require scorching temperatures around 1700°C for their formation, suggest that the magma during that period possessed the necessary heat to convert the tar into useful nitriles.
The correlation between the presence of komatiite rocks and the proposed formation mechanism indicates that nitrogen-containing compounds could indeed have been synthesized through this process, given the extreme temperatures required for komatiite rock formation.
Laboratory experiments are now essential to recreate these conditions and investigate the potential breakdown of nitrogen compounds by water, a crucial aspect that could impact the viability of this proposed pathway.
While the origin of these molecules on Earth remains uncertain, the necessity for life’s foundational components to withstand water exposure underscores the significance of understanding their synthetic pathways.
More details:
Paul B. Rimmer et al, A Surface Hydrothermal Source of Nitriles and Isonitriles, Life (2024).
Citation:
Drawing a line back to the origin of life: Graphitization could provide simplicity scientists are looking for (2024, April 18) retrieved 18 April 2024 from https://phys.org/news/2024-04-line-life-graphitization-simplicity-scientists.html
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