Third Rock from the Sun

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Anupama Nair

Man, or Homo Sapiens i.e., the name of our species is an old entry in the chakra of evolution. We are just a few billion years old and has always been fascinating field of research and now a team of scientists have now found how climate and other planetary conditions influenced human life on the surface of the earth. The climate shifts over the last 2 million years have long been believed to have a pivotal role in the evolution of homo-sapiens.

Before I write about it, let me talk about the evolution of earth and the species living in our mother, the earth. What is evolution? “Evolution in layman term is the biological change of a species over a span of time. The process of evolution keeps a species alive and thriving, and allows organisms to successfully pass down their genes. Our planet earth started as part of a ‘cloud of dust and gas’. It has evolved now into our home, which has an abundance of rocky landscapes, an atmosphere that supports life, and oceans filled with mysteries unsolved.

Billions of years ago, Earth, along with the rest of our solar system, was not all recognizable, existing only as an enormous cloud of dust and gas. “Eventually, a ‘mysterious occurrence’: one that even the world’s foremost scientists have yet been unable to determine created a disturbance in that dust cloud, setting forth a string of events that would lead to the formation of life as we know it”. The scientists were of the belief that a distant star malformed, creating a supernova explosion, which disrupted the dust cloud and caused it to pull together. This formed a spinning disc of gas and dust, known as a ‘solar nebula’. The faster the cloud spun, the more the dust and gas became concentrated at the center, further fueling the speed of the nebula. Over time, the gravity at the center of the cloud became so intense that atoms of hydrogen began to move more rapidly and violently. The protons of hydrogen began fusing, forming helium and releasing massive amounts of energy. This led to the formation of the star which is the center point of our solar system, the sun nearly 4.6 billion years ago.

The formation of the sun consumed more than 99 percent of the matter in the nebula. The remaining material began to merge into various masses. The cloud was still spinning, and clumps of matter continued to collide with others. Eventually, some of those clusters of matter grew large enough to maintain their own gravitational pull, which molded them into the planets and dwarf planets that make up our solar system today. “Earth is one of the four inner, terrestrial planets in our solar system. Just like the other inner planets like Mercury, Venus, and Mars, it is relatively small and rocky. Early in the history of the solar system, rocky material was the only substance that could exist so close to the Sun and withstand its heat.

In the beginning, earth was not at all recognizable from its modern form. “At first, it was extremely hot, to the point that the planet probably comprised almost entirely of molten magma. Over the course of a few hundred million years, the planet began to cool and oceans of liquid water formed. Heavy elements began sinking past the oceans and magma toward the center of the planet. As this occurred, Earth discriminated into layers, with the outermost layer being a solid covering of relatively lighter material while the denser, molten material sunk to the center.

Scientists believe that Earth, like the other inner planets, came to its current position in three different stages. “The first stage, is known as ‘accretion’, or the formation of a planet from the existing particles within the solar system as they collided with each other to form larger and larger bodies”. Scientists believe “the next stage involved the collision of a proto-planet with a very young planet Earth”. This is said to have occurred more than 4.5 billion years ago and may have resulted in the formation of Earth’s moon. The final stage of development saw the ‘bombardment’ of the planet with asteroids. Other events were occurring on our young planet at this time as well. It is believed that during the early formation of Earth, asteroids were continuously bombarding the planet, and could have been carrying with them an important source of water. Scientists believe the asteroids that slammed into Earth, the moon, and other inner planets contained a significant amount of water in their minerals, needed for the creation of life. It seems the asteroids, when they hit the surface of Earth at a great speed, shattered, leaving behind fragments of rock. Some scientists suggest that nearly 30 percent of the water contained initially in the asteroids would have remained in the fragmented sections of rock on Earth, even after impact.

Many hundred million years after the process i.e., around 2.2 billion to 2.7 billion years ago ‘photosynthesizing’ bacteria evolved. They released oxygen into the atmosphere via photosynthesis and, in another hundred million years later, were able to change the composition of the atmosphere into what we have today. The atmosphere is comprised of 78 percent nitrogen and 21 percent oxygen, among other gases, which enables it to support the many lives residing within it. Earth’s early atmosphere was most likely composed of hydrogen and helium. As the planet changed, and the crust began to form, volcanic eruptions occurred frequently. These volcanoes pumped water vapor, ammonia, and carbon dioxide into the atmosphere around Earth. Slowly, the oceans began to take shape, and eventually, primitive life evolved in those oceans.


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