Planetary origin of metabolisms during abiogenesis

Abiogenesis refers to a hypothetical natural process on the ancient Earth that non-living organic and inorganic matter together self-organize, forming some form of energy and chemical cycling system from which life emerged. Although the details of these distant processes are largely mysterious, it is reasonable to speculate that many features of these ancient non-living cycles should in principle share a similar pattern with modern ecosystems in existence today, even though is dominated by life.

Considering Earth as a celestial body that receives radiation energy input from the Sun at the surface. Today, this flux of energy dominates the surface energy input, at 99.8%. Certainly, throughout its existence, Earth has been shedding heat from its interior, while its rotation and surface liquid has been influenced by the Moon (tides heating). However, these two forms of energy input constitute only about 0.02% of the total energy influx. Energy from the Sun plays a much more dominant role. 70% of the solar radiation energy reaching Earth is absorbed, driving all kinds of physical, chemical and biological processes on the Earth surface. The end result is that Earth’s elemental and redox cycles have been kept away from equilibrium. For example, photosynthesis takes down CO2 while outputs molecular oxygen. The presence of low amounts of CO2 and high amounts of oxygen in the atmosphere thus represents such a disequilibrium.

Lynn Margulis, one of my favorite writers on the origin of life subject, wrote in his book “Microcosmos”, that there could be a hypothetical period of time on Earth, during which the boundary between life and non-life blurs. She referred to this as the abiogenesis period. That is, at this particular time on Earth, the non-living and the living are the same one thing. Later, the non-living and the living separated as the environment gradually diverged, driving the evolution of enclosed cellular life. Thus, cells emerged for this particular reason: environmental change. This model also suggests that the drive to form the first cell is to preserve that initial “abiogenesis environment”, whatever it might be. This model also implies that the relevant metabolisms that “defines” early life occurred prior to the emergence of cells. I find this idea and the model profound. Here I explore and propose some ways perhaps to test it scientifically.

All current known forms of life on Earth are cellular: the biosynthesis and metabolisms largely occur within a well-defined membrane structure. This membrane is also semi-permeable, allowing input and output of materials. Life, as we know it in its essence, is some metabolic activity happening on a membrane structure. This membrane structure not only is responsible for obtaining the energy required for reactions but also synthesizes, making copies of itself according to some evolvable information template. Therefore, the role of the membrane is not simply an enclosure and an environmental divider, but also a functionalized machine. At this moment in time, it is unclear if this structure appeared early or later during the abiogenesis period. It must be the case, however, some form of abiosynthesis, biosynthesis or something in between the two that is in operation during the abiogenesis period.

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