Natural Radioactivity and Chemical Evolution on the Early Earth: Prebiotic Chemistry and Oxygenation

Abstract

It is generally recognized that the evolution of the early Earth was affected by an external energy source: radiation from the early Sun. The hypothesis about the important role of natural radioactivity, as a source of internal energy in the evolution of the early Earth, is considered and substantiated in this work. The decay of the long-lived isotopes 232Th, 238U, 235U, and 40K in the Global Ocean initiated the oxygenation of the hydro- and atmosphere, and the abiogenesis. The content of isotopes in the ocean and the kinetics of their decay, the values of the absorbed dose and dose rate, and the efficiency of sea water radiolysis, as a function of time, were calculated. The ocean served as both a “reservoir” that collected components of the early atmosphere and products of their transformations, and a “converter” in which further chemical reactions of these compounds took place. Radical mechanisms were proposed for the formation of simple amino acids, sugars, and nitrogen bases, i.e., the key structures of all living things, and also for the formation of oxygen. The calculation results confirm the possible important role of natural radioactivity in the evolution of terrestrial matter, and the emergence of life.

The Carbon-Based Evolutionary Theory (CBET)

“…Figure 1 illustrates how simple CBSs, along with other substances, can form complex CBSs due to energy absorption. Certain H1-CBSs, such as HCN, CO2, and CH4, along with other materials, form H2-CBSs, like amino acids, nucleotides, and monosaccharides, through some energy-absorbing organic synthesis reactions under the laws of thermodynamics and organic chemistry [6][7][8][9][10][11][12][13][14][15]. Similarly, certain H2-CBSs, along with other materials, form H3-CBSs, like proteins, nucleic acids, and lipids, through some energy-absorbing organic synthesis reactions under the laws of thermodynamics and organic chemistry [7][8][9].…”

“…During and after the formation of Earth, H0-CBSs combined to form H1-CBSs (e.g., carbon dioxide, methane, and hydrogen cyanide). Through heat-absorbing chemical reactions, these H1-CBSs gave rise to a multitude of distinct H2-CBSs, a process that is widely accepted in modern science 12 [6][7][8][9][10][11][12][13][14][15]. The prebiotic chemical synthesis routes for various H2-CBSs found in organisms, such as amino acids, nucleotides, and monosaccharides, have been experimentally validated under geologically plausible and biologically relevant conditions in laboratories [10][11][12][13][14][15].…”

“…Through heat-absorbing chemical reactions, these H1-CBSs gave rise to a multitude of distinct H2-CBSs, a process that is widely accepted in modern science 12 [6][7][8][9][10][11][12][13][14][15]. The prebiotic chemical synthesis routes for various H2-CBSs found in organisms, such as amino acids, nucleotides, and monosaccharides, have been experimentally validated under geologically plausible and biologically relevant conditions in laboratories [10][11][12][13][14][15]. Moreover, myriad distinct H2-CBSs have been identified in meteorites, with mass spectrometry analysis of the Murchison meteorite, which fell in Australia in 1969, suggesting the presence of possibly millions of distinct CCMs [44].…”

“…MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content. 2 monosaccharides, nucleotides, proteins, and nucleic acids, could be synthesized naturally on the prebiotic Earth [7][8][9][10][11][12][13][14][15]. The concept of chemical evolution has been widely accepted, although the mechanism and processes of chemical evolution have not been fully revealed.…”

The Carbon-Based Evolutionary Theory (CBET)

“…In chemistry, in the 1920s, Alexander Oparin proposed a hypothesis suggesting that life on Earth originated through a gradual chemical evolution of organic molecules [6]. Since the 1950s, numerous experiments have been conducted to investigate how various organic molecules, such as amino acids, monosaccharides, nucleotides, proteins, and nucleic acids, could be synthesized naturally on the prebiotic Earth [7][8][9][10][11][12][13][14][15]. The concept of chemical evolution has been widely accepted, although the mechanism has not been revealed.…”