The origin of chemical complexity in space is, in addition to an open question, a fundamental aspect to understand the first steps that led to the origin of life. Now an international study, led by researchers from the Center for Astrobiology (CAB, CSIC-INTA), proposes a new approach to the origin of molecular complexity in space, making use of the theory of complex networks.
The authors, who publish their work in the journal PNAS, explain the appearance of complex molecules in the clouds of the interstellar medium from a novel point of view: as an emergent process typical of complexity theory, used in fields such as sociology and computing and that explains collective phenomena as diverse as traffic jams or avalanches.
The team has created a theoretical and computational environment, called NetWorld, where the interaction between complex networks that can represent any simple structure, be it chemical, biological or social, is simulated.
The results show that, in ‘wild’ environments, only the simplest pieces of this kind of LEGO are created. However, when the environment softens, these basic pieces actively interact, drastically giving rise to an enormous diversity of compounds, which will later represent the fundamental bricks of structures on a larger scale and in increasingly complex systems.
This system does not try to simulate the rules of real chemistry nor does it make use of real data, but as lead author Jacobo Aguirre of the CAB points out, “what is surprising is that if we understand the nodes of our networks as atoms and each network as a molecule , NetWorld is able to describe the starting point in the origin of life process: the emergence of complexity in the evolution of chemical diversity in the interstellar medium.”
The connection between the extreme simplicity of the model and its ability to describe real phenomenology of astrobiological relevance suggests that many of the basic properties of the long road from space chemistry to prebiotic chemistry and ultimately to life as it is as we know it, might show simple and universal patterns.
NetWorld and game theory
The NetWorld environment models the evolution of complex network structures (nodes joined by connections) towards complexity. The rules of interaction between these networks, which allow them to grow and evolve, are very simple and have been extracted from game theory: each node competes with the rest to be well connected in the network as a result of the interaction.
So the rules have nothing to do with real chemistry or biology, but rather abstract “network chemistry”. NetWorld predicts a sharp transition from a simple network “biodiversity” (a few different networks of small size) to a much more complex one (thousands of different networks of very different size and complexity) when the parameter representing the environment reaches a critical value.
This transition is observed in different areas of astrobiology, so NetWorld is able to describe this fundamental property of the chemistry of the origin of life from a truly novel point of view, the authors insist.
Similar astrophysical and computational environment
This is because in this astrophysical environment the phenomenology is similar to that of the Networld computational environment: when interstellar clouds condense, interstellar dust shields the ultraviolet light that hinders many chemical reactions, and the molecules created up to that moment interact giving rise to to dozens of new, much more complex molecules.
“There is a drastic transition towards complexity in the two systems, and the properties of these two transitions are equivalent,” says co-author Fernando Puente-Sánchez, a researcher at the Swedish University of Agricultural Sciences.
According to the computational model, the abundance of structures that are created is proportional to the number of paths that give rise to each structure. Thus, a hitherto unknown proportional relationship has been found between the actual molecular abundances of the different molecules in dark clouds (such as hydrocyanic acid –HCN–, ammonia –NH3– and others) and the potential number of chemical reactions that generate them. as product.
Therefore, “NetWorld promises to be a novel bridge between astrochemistry and complexity theory”, concludes CAB astrochemist Izaskun Jiménez-Serra, also a co-author of the article.
Reference:
M. García-Sánchez, J. Aguirre et al. ‘The emergence of interstellar molecular complexity explained by interacting networks’. ‘Proceedings of the National Academy of Sciences’ (PNAS), 2022.
