Dear Colleagues,
In the past three decades, research on the question of how and where the origin of life (OoL) might have occurred on Earth some four billion years ago has made great strides. Perhaps the most significant is the emergence of a number of alternative hypotheses that can be subject to experimental testing. Researchers are now focusing their attention on several geological settings that could support key prebiotic chemical processes in two of the leading OoL hypotheses: in salt water at hydrothermal vents in the ocean or in cycling fresh water hydrothermal pools on land. In addition, a number of other venues and scenarios have been proposed and are being investigated. Simultaneously, work in computer simulation and developments from emergent phenomena in complex systems have provided insight into the basic principles that might be required in abiogenesis. Finally, life detection missions to Mars and the icy moons of Jupiter and Saturn as well as the detection of biosignatures on exoplanets have intensified interest in the conditions and settings in which life can begin.
We therefore find ourselves with much more solid scientific footing to proceed with an accelerated program of testing of OoL hypotheses at the beginning of the 2020s, both in clean, laboratory settings and in field sites, which are analogs for early Earth, Mars, or water worlds. Equipment for use in the laboratory and the field has enabled a new generation of researchers to truly “push the limits” in testing OoL scenarios. In a 21st-century version of the famous Miller–Urey experiments, planetary atmospheres, and mineral surfaces can now be emulated inside chambers, and laboratory-based cycling hot spring simulators are being built by groups. Recent issues of the journal Astrobiology have focused on hot springs as hypothesized sites for the origin of life (Damer and Deamer, 2020), while other groups have advanced hypotheses and the in-laboratory testing of oceanic vent settings (Barge and White, 2017).
To guide authors, at the 2017 Astrobiology Science Meeting, the following language was developed and adopted to describe a crucial experiment (per Platt, 1964), which can be applied to test any origin of life hypothesis: Confirm or falsify a non-enzymatic process by which catalytic and replicating systems of polymers are produced under plausible prebiotic conditions that also support cycles of combinatorial selection in which encapsulated sets of these polymers emerge and begin to evolve.
This language can be used as a template for OoL experiments to directly test hypothesized scenarios. There are also a number of ancillary experiments, which can provide valuable insights into problems that do not meet the criteria of the crucial experiment. Experiments might employ inorganic or other compounds not deemed plausibly present on the prebiotic Earth. Experiments can also be carried out with the tools of synthetic biology to design minimal protocells or progenotes. These experiments can “jump the queue” and shed light on the challenges and probabilities of informational or catalytic functional polymers arising from an initial pool of random sequences. In addition, computer simulations of abstract characteristics of self-maintaining and replicating chemical systems can provide guidance to experimenters.
Topic areas for this Topical Collection include:
- Meteoritic, atmospheric, hydrothermal, and mineral-sourced material contributions to prebiotic chemical systems;
- The non-enzymatic polymerization of RNA-like, DNA-like, and proto-peptides through wet–dry cycling, mineral interaction, and other methodologies;
- Sources of lipids and mechanisms for the membranous encapsulation of polymers to form protocells;
- Studies of polymer–membrane colocalized systems as the initial landscape for a quasi-biological world;
- Proposals, models, and experiments demonstrating mechanisms to replicate systems encoding heritable traits;
- Synthetic minimal cells and protocells;
- Protocell to protocell competition and cooperation;
- Non-membranous forms of encapsulation: coacervates, emulsion droplets of hydrocarbons, oligonucleotide origami, mineral surfaces, rock pores, and mineral gels;
- Non-traditional solvents and “weird life” origins scenarios;
- Testing of the RNA-world hypothesis through in vitro evolution;
- Testing of the hot spring hypothesis through protocell self-assembly and combinatorial selection;
- Testing the submarine vent hypothesis through carbon fixation of monomers within pressure vessels and microfluidics simulations of vents;
- Models and experiments for the first energy-driven metabolic circuits including autocatalytic sets;
- The spontaneous emergence of reaction networks driven by radiolytic and other energy sources;
- Testing models for a proto-ribosome and distributed mechanisms enabling translation in silico and in vitro;
- Models for complex emergent systems as applied to OoL;
- Computational simulations of rates of polymer formation and degradation in monomer soups;
- Analytical techniques and tools to analyze products of OoL experiments including: microscopy, gels, HPLC, nuclear and X-ray imaging, AFM imaging;
- Automating and scaling throughput of synthetic protocell experiments;
- Portable devices to enable OoL experiments in the field;
- Bringing the hot spring into the laboratory: complex benchtop devices;
- Early life rock record and its application to understanding the period of life's emergence (the "Progenean");
- OoL-informed biosignature detection for surface missions on Mars;
- OoL-informed biosignature detection in plumes from icy moons;
- OoL-informed atmospheric biosignature detection on exoplanets.
The journal is pleased to be publishing its first Topical Collection dedicated to testing origin of life hypotheses not only in the traditional laboratory setting, but also at field analog sites.
This Topical Collection of
Life welcomes the submission of unpublished original work or reviews on previous work. We plan to receive submissions for a nine-month period from 15 Sept 2020 to 15 July 2021.
References
Damer, B.; Deamer, D. The Hot Spring Hypothesis for an Origin of Life. Astrobiology 2020, 429–452. http://doi.org/10.1089/ast.2019.2045
Barge, L. and White, L. Experimentally Testing Hydrothermal Vent Origin of Life on Enceladus and Other Icy/Ocean Worlds. Astrobiology 2017, 17, 820-833. http://doi.org/10.1089/ast.2016.1633
Platt, J.R. Strong Inference. Science 1964, 146, 347–353.
Dr. Bruce Damer
Collection Editor
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