Hadic Aeon

The hadic eon, also known as hadean or hadean, is the oldest period on Earth. Comprehends from the formation of the Earth about 4.550 billion years ago to about 4.000 / 3.800 billion years ago. The period is not entirely exact, but an informal one because these boundaries have not been officially established or recognized. The commission responsible for establishing the boundaries and studying the stratigraphy, geology, and geochronology on a global scale is the International Commission on Stratigraphy.

This period, so unknown, is at the same time the starting point of our planet. It is estimated that the entire solar system was probably forming in the midst of a large cloud of gas and dust. The Hadean eon is also the period in which Earth undergoes great changes. Due to large volcanic eruptions, and even the time when the Earth and many inner planets of the solar system were hit by huge asteroids. One of them was the Moon hitting the Earth (which we talked about recently, in curiosities of the Earth, point 5).

Evidences of the Hadic Aeon

Searching the oldest rocks, we are going to Greenland, Canada and Australia. These rocks are 4.400 billion years old. and are highly relevant to the study of the Hadean Eon, as they offer insight into the beginning of the Earth. Hadean rocks, discovered in the final decades of the 20th century, are individual zircon crystal minerals. Although they are the oldest known minerals, and are buried deep beneath sediments in western Canada and the Jack Hills region of Western Australia, they do not belong to rock formations.

The oldest rock formations that are known date from ago 3.800 million yearsThe oldest known is found in Greenland, known as the «supracortical belt of Isua». They are somewhat altered by volcanic dikes that penetrated the rocks after they were deposited. In the book "Conceptions of the Origin of Life" by Diego Sebastián González and Maricel Ciela Gutiérrez, we find, with technical but very magical data, one of the questions we have always asked ourselves: Where does life begin? And there it is, the first early evidence, in the Isua supracrustal belt, in the Hadean Eon. You can also read about the Archean eon to understand how the history of the Earth continued.

The Origin of Life on Earth

Greenland sediments contain banded iron formations. Initially, it was thought that they possibly contained organic carbon, indicating that the first self-replicating molecules were likely the beginning of their existence. Now, there is early evidence that life comes from the Isua supracortical belt, West Greenland, and also the Akilia Islands, in the same area. It must be kept in mind that, although scientific evidence was found in that area, we cannot point it to the past. Let us remember that the Earth had not only just formed, but that almost after its formation, the movement of the continental plates continued. You can also consult about the history of the cardinal points which has also been influenced by these events.

The rock formations that comprise it have a concentration of -5,5% of Carbon (C) 13, C13. This is due to the biotic environment, which prefers the lighter C12 isotope. C13 in biomass has concentrations of -20 and -30, much lower than the concentrations found in the rock formations. Based on these techniques, it is speculated that life on our planet could actually begin 3.850 million ago years, at the end of the Hadean eon, which coincides with the interest in understanding more about the different geological periods and its relationship to the origin of life on Earth.

The beginning of the water

It is considered that among the particles with which the planet was formed, there must have been a certain amount of water. These molecules should not have succumbed to gravity, and moving away from the center, they remained on its surface. After the planet reached 40% of its formationThese water molecules, together with other highly volatile ones, must also have been found on the surface, in very large quantities already. The lack of many noble gases that must have escaped is striking, such as helium or hydrogen. This led to the belief that something catastrophic must have happened in the early atmosphere. Among the hypotheses, we have the Theia theory, which we discussed in that article, which explained why the Moon exists as such. In addition, you can read about the composition of the asteroid belt which could be related to these events.

Its catalytic effect on life

Suggestions as to how water acted as a catalyst were first put forward by Lazcano and Miller in 1994. The connection, they explained, would be due to the circulation of water through oceanic vents. The total recirculation time would last 10 million years, but all organic compounds could be destroyed at temperatures above 300°C. Thus, after this gradual cooling, a primitive organism DNA-protein heterotroph with a genome of 100 kilobases, it would take about 7 million years to end up evolving to a cyanobacterial genome with 7.000 genes. This process, as it relates to the aquatic environment, is also linked to studies of bioluminescence in marine animals that could have had their origins in these stages.

And there is something that we have not said, that perhaps one day will receive an answer. Today is still the big question to answer. Life, as far as is known, can only exist in the form of carbon or siliconOn our planet, it exists as carbon, not silicon; who knows, maybe it does elsewhere. But the real question is, how could life have developed if the probability of it happening was practically zero?

It's inevitable that if we think about it at night, we raise our gaze to the stars, allowing ourselves to be invaded by the great thoughts that emerge.

After the Hadean eon, the eon continued. If you're interested in learning how it continued, click here.