Alternative solvents for life: framework for evaluation, current status, and future research

Bains, William, Petkowski, Janusz J. and Seager, Sara 2024. Alternative solvents for life: framework for evaluation, current status, and future research. Astrobiology 24 (12) , pp. 1231-1256. 10.1089/ast.2024.0004

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Abstract

Life is a complex, dynamic chemical system that requires a dense fluid solvent in which to take place. A common assumption is that the most likely solvent for life is liquid water, and some researchers argue that water is the only plausible solvent. However, a persistent theme in astrobiological research postulates that other liquids might be cosmically common and could be solvents for the chemistry of life. In this article, we present a new framework for the analysis of candidate solvents for life, and we deploy this framework to review substances that have been suggested as solvent candidates. We categorize each solvent candidate through the following four criteria: occurrence, solvation, solute stability, and solvent chemical functionality. Our semiquantitative approach addresses all the requirements for a solvent not only from the point of view of its chemical properties but also from the standpoint of its biochemical function. Only the protonating solvents fulfill all the chemical requirements to be a solvent for life, and of those only water and concentrated sulfuric acid are also likely to be abundant in a rocky planetary context. Among the nonprotonating solvents, liquid CO2 stands out as a planetary solvent, and its potential as a solvent for life should be explored. We conclude with a discussion of whether it is possible for a biochemistry to change solvents as an adaptation to radical changes in a planet’s environment. Our analysis provides the basis for prioritizing future experimental work to explore potential complex chemistry on other planets

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	Mary Ann Liebert
ISSN:	1531-1074
Date of First Compliant Deposit:	10 February 2025
Date of Acceptance:	12 November 2024
Last Modified:	10 Feb 2025 10:00
URI:	https://orca.cardiff.ac.uk/id/eprint/174776

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