pls make it brainliest answer i wrote it very big because same topic is going on now
Life's Origins
In 1864, Louis Pasteur described his experiments showing that microbial life could not originate spontaneously in the absence of preexisting life. This work is considered a landmark in modern science because it settled a longstanding controversy over spontaneous generation
Spontaneous generation is the idea that organisms could form miraculously from non-living material.
But Pasteur's results posed a new riddle for evolutionary biologists: If life could only arise from life, how did living organisms initially appear on the planet?
The answer came in the 1920's when A.I. Oparin of Russia and J.B.S. Haldane of England independently presented compelling arguments that the origin of life could be explained, not as the result of rapid spontaneous generation of whole organisms in a few weeks, but from a long and gradual process of chemical evolution.
Much progress has been made since the 1920's, but, as with most complex scientific questions, many uncertainties remain and many new avenues of inquiry have been uncovered.
Today, research into the origin of life is interdisciplinary with workers trying to answer four main questions:
1. What was the Earth's physical environment like when life first evolved?
2.What sorts of chemical reactions could produce the building blocks of life and could these occur naturally in the early Earth's environment?
3. How could the complex organic molecules be compartmentalized into a contained unit?
4. How did the genetic code evolve?
What Was The Earth's Early Environment?
Life has dramatically changed the Earth. Organisms have altered the composition of the atmosphere, affected the types and concentration of minerals and ions in the seas, and even worked and churned the soil. So, if we want to understand the conditions in which life first appeared, we cannot rely on just an examination of present day Earth. We use two pieces of information:
1. Rocks buried deep in earth.
2. The four inner, or terrestrial, planets (Mercury, Venus, Earth and Mars) and our moon were formed from similar materials in the same way. Because they have a similar history, anything we learn about the formation of Mars, Venus, Mercury, or the moon will inform us about early Earth.
This is what we know:
Our solar system formed about 4.6 billion years ago (abbreviated b.y.a.) when a swirling cloud of gas and dust began to contract.
In the early years after the formation of the solar system, the terrestrial planets continued to be bombarded by smaller bodies of various sizes as the last of the particulate material from the formation of the planets was swept-up by their gravitational pull.
This bombardment, measured from radioactive dating of the moon's craters, and by comparing lunar, martian, and mercurian cratering records, gradually declined in intensity until it reached present-day levels about 3.5 billion years ago.
The effect of the bombardment on the origin of life was significant. Bombardment affected:
1. the temperature of the early Earth
2. the composition of the atmosphere
3. delivered biogenic elements to Earth (biogenic elements are those chemicals common to all living organisms - like phosphates)
4. Finally, the high energy released could also have delayed the origin of life.
Let's look at each of these effects in more detail:
About 3.9 bya, the earth had solidified but the violent bombardment would have prevented the continuous existence of life on the planet before 3.8 billion years ago. Large impacts would have produced globally lethal conditions by boiling large volumes of ocean water effectively sterilizing the surface of the planet with steam.
