Origin of Life: The Earth and the Making of the Atmosphere

Some questions, such as the origin of life, run the human imagination. There is great variety in the answers that religion, mythology, and philosophy suggest for this topic. Most of them share the assumption of attributing the event to a creator outside of nature. As a widespread opinion, species diversity has been defined as the result of the individual, pre-thought works of the creator. Until the late nineteenth century, there was no theory of evolution by natural selection, a true scientific (i.e., testing) explanation that could explain the origin of species. Can twentieth-century science do the same about the origin of life?

Origin of Life

In the biogenesis hypothesis, there are principles that a living thing can only be formed from a living thing, and Pasteur’s classical experiment is given as an example as the proof of this principle. Pasteur’s work pushed aside the notion of spontaneity that many biologists had advocated for many years. Scientists are no longer seriously concerned that maggots are formed from spoiled flesh, or that earthworms are formed from soil during a heavy rainfall. Nor could they be more concerned with the way of thinking that the mice consisted of a damp shirt left in a dark, wheat-sprinkled corner, or that microorganisms emerged spontaneously from boiling broth. So it may be surprising that in the last quarter of the twentieth century, spontaneous formation was one of the main points of interest in biology. However, there is a striking difference between the idea of ​​spontaneous formation in our time and the idea of ​​spontaneity in Pasteur’s time. Today’s theorists do not advocate that life can arise spontaneously in today’s world. The main argument of the spontaneous formers is that under the conditions prevailing in the world at the beginning, life could and was formed from inanimate matter, and that all life forms existing in the world derive from such a root.

Let us clarify a theory about the origin of life that is widely accepted by scientific circles. The basis of this theory was first expressed clearly and effectively in 1936 by the Russian biochemist A. I. Oparin. Although the theory has been established with a lot of evidence, many of its details can be discussed. Because there is no direct evidence of the origin of life.

Earth and the formation of its atmosphere

The explanations about how the solar system came into being are not satisfactory; we only have some hypotheses. But as astronauts dig deeper into the mysteries of the universe and gather more evidence, some of these hypotheses are increasingly plausible. According to one of the most widely accepted theories today, the universe is 20 billion years old, and the sun and its planets formed four and a half to five billion years ago from clouds of cosmic gas and dust. Most of this substance condensed into a single mass producing very high temperature and pressure, initiating thermo-nuclear reactions and turning the condensed mass into a sun. Smaller clouds began to condense in the residual cloud of gas and dust forming a disk in the gravitational field of the newly formed sun. These small clouds formed the earth and other planets. After all, billions or even trillions of “dirty snowballs” up to several kilometers in diameter, further out of Pluto’s orbit, are thought to encircle the solar system. This distant cluster of bodies, called the Oort cloud, is the source of comets that many researchers believe are drastically changing the course of evolution.

As the world becomes denser, its components show a stratification. Heavy elements such as iron and nickel have shifted towards the center and lighter materials are more concentrated near the surface. Hydrogen, helium and noble gases from light substances must have formed the atmosphere first. However, unlike the big planets like Jupiter and Saturn, the Earth was very small and the gravitational field of Earth was too weak to hold the atmosphere at first; In the end, all the gases fled into space, leaving a bare rocky world behind, without oceans and atmosphere. However, with the decrease of gravitational pressure and radioactivity in the world over time, very high temperatures occurred and the inside of the earth began to melt. With the effect of this, an inner core of iron and nickel, a mantle of approximately 4700 km thick consisting of dense iron and magnesium silicates and an outer shell of 8-65 km consisting mainly of light silicates was formed. At the same time, the intense heat in the earth’s interior tended to expel various gases that were primarily formed by volcanic activity. These gases created a second atmosphere for the world.

In order to understand the conditions under which life occurred, it is necessary to know something about the possible first composition of this secondary atmosphere. Today’s atmosphere contains about 78% molecular nitrogen (N), 21% molecular oxygen (O2), 0.33% carbon dioxide (CO2) and small amounts of rare gases such as helium and neon. However, the data obtained show that the atmosphere did not contain any free oxygen in the first period of its formation and therefore did not have an oxidizing quality like the present atmosphere. In recent years, two main models of the composition of the atmosphere have been established first; Both models fit the contemporary hypothesis about the origin of life.

According to Oparin’s model, the first atmosphere was a reducing atmosphere containing large amounts of hydrogen (H2). Consequently, some of the atmospheric nitrogen is probably ammonia (NH3); oxygen was water vapor (H20) and carbon was primarily in the form of methane (CH4).

Initially, most of the earth’s water was probably in the form of water vapor that caused heavy rains in the atmosphere. This steam then filled the pits in the form of water and first formed the oceans. As the rivers flowed down the slopes, together they dissolved salt and minerals (iron and uranium, both of particular significance), carried to the seas, and these minerals gradually accumulated in the seas. Most likely atmospheric gases also dissolved in the newly formed ocean waters. All free oxygen that could be found in the atmosphere was rapidly oxidized and removed by ions dissolved in the ocean. The rich uraninite (UO2) deposits from this time must have been formed in this way.