ABSTRACT
Life may have emerged on Earth about 4 billion years ago, but the actual pathways of biogenesis are still shrouded in mystery. A new model for the symbiotic origin of life in hydrothermal crater lakes is proposed previously. In this scenario, life arose through five hierarchical stages of increasing molecular complexity: cosmic, geologic, chemical, information, and biological. In this paper, the first two stages—cosmic and geological—are discussed in detail. In the cosmic stage (≥4.6 Ga), the building blocks of life had their beginnings in interstellar space. Both comets and carbonaceous chondrites delivered the building blocks of life and water to early Earth. Meteorite collisions that created hydrothermal crater lakes in the Eoarchean crust inadvertently became the perfect crucibles for prebiotic chemistry, filled with cosmic water and the building blocks of life. In the geologic stage (4–3.2 Ga), the oldest greenstone belts of Canada, Greenland, South Africa, and Australia show the earliest evidence of thermophilic life in hydrothermal environments. An attractive site for life’s beginning would be a network of complex crater lakes with hydrothermal systems that served as the crucibles for prebiotic synthesis and biogenesis. In these hydrothermal crater lakes, cosmic and terrestrial chemicals were mixed, concentrated, and linked together by convection currents, powered by hydrothermal, solar, tidal, and chemical energies, where life began to brew.
