It was great to be contacted by Jason for a comment on a recent work of Criado-Reyes and collaborators (and therefore be within the first to see the article). This work shows how something basic and often ignored, i.e. glassware, can affect our interpretation and understanding of chemical processes. The impact is significant here.
In 1952, Stanley Miller and Harold Urey have conducted a rather simple experiment to validate 1930s primary abiogenesis hypothesis by Oparin and Haldane, stating that conditions on early Earth would promote reactions towards the chemical complexity and the emergence of life (i.e. against Pasteur’ theory of biogenesis that life can originate only from pre-existing life). In their setup, Stanley and Harold unknowingly and fortuitously included another important component — silicate surface of the flask, through this incorporating the effect of mineral surfaces, as postulated in 1949 by Bernal, into their famous experiment.
Criado-Reyes, J., Bizzarri, B.M., García-Ruiz, J.M. et al. The role of borosilicate glass in Miller–Urey experiment. Sci Rep11, 21009 (2021). https://doi.org/10.1038/s41598-021-00235-4
When we think of chemistry, we often imagine a laboratory bench full of test tubes and a scientist in a white coat. But as we accumulate knowledge through such experiments, we start to formulate them into theories and hypothesis. Testing such hypotheses allows us to refine our theories, ultimately gaining predictive power. Additionally, computational chemistry methods provide us with a versatile tool, bringing atomic-level insights to processes beyond conditions attainable in the lab. It comes as no surprise that it is extensively applied for the search of chemical processes of the origin of life.
In this search, we are biased towards “life as we know it” – made of polymeric self-organising sequences in an aqueous media confined by a flexible lipid membrane. Life forms of this kind would only exist in Earth-like conditions, giving rise to the interest in planets in the “habitable zone” (planets that can have liquid water on their surface).
Titan, the moon of Saturn, with a cryogenic surface (-180 °C) cannot have liquid surface water. Instead, it has hydrocarbon (that exists as natural gas on our planet) seas, and it snows benzene. It also has a dense atmosphere with a wide diversity of organic molecules produced through photochemical reactions. It opens a playground for the ideas of exotic life.
Indeed, when recreating the chemistry of the Titan’s atmosphere, Horst et al. were able to observe the formation of nucleotides and amino acids, essential building blocks of polymers of our life. The significance here was that these core reactions, first discovered in Miller-Urey experiment, and believed to require water, could go on without it.
Furthermore, Stevenson et al. then postulated the possibility of formation of pseudo-membranes in liquid-water-free environments, by such aiming to expand the search for life beyond “habitable zone”. As an example, they studied self-assembly of molecules found on Titan. Within those, acrylonitrile was predicted to form a flexible inverse-membrane, named azotosome.
However, recent theoretical work by Sandström and Rahm curbs our excitement for finding traces of exotic life. Through molecular modelling, they studied other plausible structures that acrylonitrile could adopt in Titan’s frigid environment, where entropy plays a very small role. They demonstrated that its crystal is significantly energetically more stable than its membrane-like azotosome.
These two works demonstrate how, through computational chemistry, we can test and challenge new ideas in conditions unattainable on Earth. As a result, we are growing and evolving our understanding of the physicochemical processes and engaging in extensive discussions on the processes of life.
Computational methods are advancing, giving us the capacity to analyse the chemical space with increasing efficiency and to drive our imagination further, germinating new ideas.
