Abstract
Critical to the origin of life are the ingredients of life, of course, but also the physical and chemical conditions in which prebiotic chemical reactions can take place. These factors place constraints on the types of Hadean environment in which life could have emerged. Many locations, ranging from hydrothermal vents and pumice rafts, through volcanic-hosted splash pools to continental springs and rivers, have been proposed for the emergence of life on Earth, each with respective advantages and certain disadvantages. However, there is another, hitherto unrecognized environment that, on the Hadean Earth (4.5–4.0 Ga), would have been more important than any other in terms of spatial and temporal scale: the sedimentary layer between oceanic crust and seawater. Using as an example sediments from the 3.5–3.33 Ga Barberton Greenstone Belt, South Africa, analogous at least on a local scale to those of the Hadean eon, we document constant permeation of the porous, carbonaceous, and reactive sedimentary layer by hydrothermal fluids emanating from the crust. This partially UV-protected, subaqueous sedimentary environment, characterized by physical and chemical gradients, represented a widespread system of miniature chemical reactors in which the production and complexification of prebiotic molecules could have led to the origin of life. Key Words: Origin of life—Hadean environment—Mineral surface reactions—Hydrothermal fluids—Archean volcanic sediments. Astrobiology 18, 259–293.
Highlights
We briefly overview the basic requirements for prebiotic chemistry and the emergence of life, underlining the importance of the mineral world, in particular for the former
The objective of our study is to show, using an examination of Paleoarchean volcanic sediments strongly influenced by hydrothermal fluids as a benchmark, that volcanic sediments could have played an important role in prebiotic chemistry and in the increasing complexity of prebiotic chemical systems eventually leading to the origin of life
We briefly described the different scenarios proposed for the emergence of life, ranging from subaerial springs (e.g., Mulkidjanian et al, 2012a, b), volcanic island coastal splash pools (Fox and Strasdeit, 2013), pumice rafts (Brasier et al, 2011, 2013), to submarine hydrothermal vents (Baross and Hoffman, 1985; Russell and Hall, 1997; Martin et al, 2008; Sleep et al, 2011; see review in Dass et al, 2016) and addressed their significance with respect to what could have been the Hadean environment
Summary
We briefly overview the basic requirements for prebiotic chemistry and the emergence of life, underlining the importance of the mineral world, in particular for the former. We consider various previously proposed environments in which life might have arisen. With this background, the objective of our study is to show, using an examination of Paleoarchean volcanic sediments strongly influenced by hydrothermal fluids as a benchmark, that volcanic sediments could have played an important role in prebiotic chemistry and in the increasing complexity of prebiotic chemical systems eventually leading to the origin of life. When considering the local environment (or environments) in which life could have emerged, the prebiotic processes that led to the origin of cellular life and the physical and chemical conditions in which these processes could occur need to be taken into account.
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