THE ORIGIN OF LIFE BY MOLECULAR SYMBIOSIS AT HYDROTHERMAL IMPACT CRATER LAKES

Meteoritic impacts on the Eoarchean crust at the atil end of the Heavy Bombardment Period might have played important roles in the origin of life. Giant collisions that created hydrothermal crater lakes on early Earth inadvertently became the perfect crucibles for prebiotic chemistry and the emergence of life. In this scenario, life arose from unique mixtures of extraterrestrial organic compounds and vent spewing gases in crater basins through four hierarchical stages that created increasingly complex biomolecules. In the cosmic stage (~4 Ga) meteorite bombardments seeded ancient Earth with building blocks of life that accumulated in the hydrothermal impact crater lakes. In the geologic stage cosmic and terrestrial chemicals were mixed and concentrated in sequestered crater basins, powered by hydrothermal, solar, tidal, and chemical energies. Eoarchean Greenstone belts in Greenland, Australia, and South Africa possibly represent the relics of these primordial craters, where the oldest thermophilic fossils (≥ 3.5 Ga) have been discovered. In the chemical stage the heat churning the water inside the craters mixed thoroughly organic compounds and reduced gases and caused simple biomolecules to grow into larger, more complex ones by chain reaction. The dual origin of the ‘RNA-protein world’ is more plausible than the popular ‘RNA world.’ Once the lipid membranes encapsulated RNA and protein molecules, they began to interact and initiate serial endosymbiosis that ultimately gave rise to various cell components including plasma membranes, ribosomes, customized RNA and proteins, and finally DNA with rudimentary genetic code. In the biological stage, reproduction of protocells was the key breakthrough in the emergence of first cells. Viroids and prions possibly represent the evolutionary relics of the RNA-protein world that survived as parasites of cellular organisms for billions of years. Future experiment on encapsulated viroids and prions has a potential to create a simple synthetic cell and may confirm the vestiges of the ‘RNA-protein world.’