How Did Life Begin on Earth?

How did life begin? Every living thing on earth shares DNA. This means we are all related, our origin rooted somewhere billions of years ago to some primordial bacterium. But how did this bacterium come into being if there was no life before it? The answer is not certain, but there are some pretty interesting theories.

There is only a limited mix of chemicals that have the potential to lead to organic prebiotic (not-yet-living) molecules that eventually give rise to basic life forms. These chemicals include reduced nitrogen compounds, ammonia, methane, and water. The Miller-Urey experiment was among the first experiments that tried to understand how early Earth’s harsh environment could have given rise to prebiotic molecules using a mix of chemicals and other processes such as heat and electricity to stimulate early Earth’s atmosphere and oceans. However, it is now believed that early Earth had a far different chemical composition than what was used in the Miller-Urey experiment.

How Did Life Begin?

Miller–Urey experiment - Wikipedia
The Miller-Urey experiment.

For instance, early Earth’s atmosphere and oceans had far too much carbon dioxide, carbon monoxide, and water to facilitate the advent of prebiotic molecules. The amount of nitrogen available to the primitive Earth was also too low, despite the submarine vent systems that would have provided a variety of chemicals, including nitrogen compounds. It is believed that there could be other origins of prebiotic compounds, namely from nebular dust. This belief has since been studied.

Using nebular iron silicate condensate as a catalyst that is most similar to what would be found in solar nebulae, the iron silicate was exposed to high temperatures of about 500 kelvin (K) to 900K and underwent both the Fischer-Tropsch experiment and the Haber-Bosch experiment. The Fischer-Tropsch experiment consisted of converting carbon monoxide and deuterium to nitrogen and water, while the Haber-Bosch experiment involved the creation of ammonia from deuterium and dinitrogen. The experiments yielded surprising results when carbon monoxide, deuterium, and dinitrogen simultaneously reacted and resulted in the synthesis of various nitrogen organics such as methyl amine, acetonitrile, and N-methyl methane imine, which are involved with the creation of the building blocks of life.

how did life begin

These results not only have consequences for the early Earth, but also for any part of space that has decent amounts of nebular dust. If nebular dust was able to catalyze organic prebiotic molecules that reached Earth to eventually give rise to basic and complex life forms, it may be reasonable to assume that most of the universe’s contents ranging from meteors, planetesimals, moons, and planets may have at one time or another harbored the building blocks of life obtained from nebular dust. Furthermore, if certain celestial objects were able to hold onto prebiotic molecules from solar nebulae, there may be a possibility that life could have independently evolved many times throughout the universe if the life forms were able to accommodate the host object’s environment.

The Details

But how did life begin exactly? The researchers of this study provided detailed explanations of what they proposed to analyze, how they proposed to study it, what their results were, and the conclusive significance of those results, all of which are important factors of a scientific paper. They described what chemical components and environmental conditions would be needed for organic prebiotic molecules to naturally arise, and elaborated that since early Earth’s environment and composition was far different than what the Miller-Urey experiment utilized, it could be assumed that prebiotic molecules likely did not arise on earth and that the Muller-Urey experiment was not accurate for what it was testing. Instead, the researchers turned to the possibility of solar nebulae as being the origin of prebiotic molecules as the nebulae naturally had ideally high temperatures and were composed of many imperfect iron silicate grains with substantial surface areas that would have been perfect surfaces for various chemical reactions to take place.

An asteroid, possibly the size of LAX, will fly by the Earth in April - The  Jerusalem Post

Using the Fischer-Tropsch and Haber-Bosch experiments to replicate the environmental and chemical conditions of nebular dust, including iron silicate dust, also known as “smokes,” as a catalyst and a material analogous to nebular dust, the researchers were able to synthesize various organic compounds The Fischer-Tropsch technique was typically involved in the synthesis if methane compounds while the Haber-Bosch technique was directed more towards the synthesis of ammonia compounds, both of which had uses in other fields such as for explosive manufacturing, fertilizer, and gasoline syntheses before being used to examine how their chemical reactions could have had potential in the early solar system.

More than 50 of these experiments were conducted over a period of 12 months with the typical length of the individual experiments running from 1 day to a few weeks, with several different temperature ranges and iron silicate smokes being used for various experiments. The results found that the iron silicate smokes were successful catalysts of organic prebiotic molecules along with the assistance of dinitrogen, deuterium, and carbon monoxide, which the researchers found surprising because the iron silicates were unlike any of the metals used in typical Fischer-Tropsch experiments.

This study is particularly important for a variety of reasons. For example, since silicates are so ubiquitous in the solar nebula, the researchers conclude that it may be possible for there to be a large amount of prebiotic molecules present in the nebular dust. Furthermore, since nebular dust often leads to the formation of planetesimals, moons, and sometimes even planets, it may also be a possibility for the building blocks of life and perhaps even life itself to have existed on other celestial objects.

So, how did life begin? Now you know.

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