How did life begin on earth?

Science Report

This is the first report on this blog.

So the topic of today’s report is 

How did life on Earth begin?

Introduction 

First of all, the earth formed about 4.5 billion years ago. Within a billion years, life on earth began. The first microorganism was found in the ocean. Through a process, we’ll discuss later.

Formation of our planet Earth

The planets and the sun in our solar system were made when a solar nebula collapsed by gravitation, which began to spin and flatten in a pancake-like shape disc also called a circumstellar disc. Then the sun and the planets grew out of that disc.

It is also speculated that a “Mars-sized” object called ” Theia” collided with early earth, fragmenting the surface of the earth to form the moon.

Do you know: It took 70-100 million years to form the earth.

Where did the water come from?

The simple answer is through volcanic activity and the release of gases that were trapped underneath the earth surface.

This water vapour condensed to form water on the surface of the earth.

Another theory is that through the ice and water of comets and asteroids slamming the surface of the earth, the oceans came.

Both theories hold as there was a so-called ” Late Heavy Bombardment” of asteroids, while the formation of the “then not so green” planet.

Tectonic plates

As the molten outer layer of Earth cooled it formed the first solid crust, which is thought to have been rich in minerals like quartz in its composition. The first continental crust, which was made up of igneous rocks in composition, formed by the partial melting of this crust.  There are two main models of how this initial small volume of continental crust evolved to reach its current abundance: (1) a relatively steady growth up to the present day, which is supported by the radiometric dating of continental crust globally and (2) an initial rapid growth in the volume of continental crust during the period, forming the bulk of the continental crust that now exists. The two models and the data that support them can be reconciled by large-scale recycling of the continental crust, particularly during the early stages of Earth’s history.

New continental crust forms as a result of plate tectonics, a process ultimately driven by the continuous loss of heat from Earth’s interior. Throughout hundreds of millions of years, tectonic forces have caused areas of continental crust to group together to form supercontinents that have subsequently broken apart. At approximately 750 Million years, one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia at 600–540 Million years, then finally Pangaea, which also began to break apart at 180 million years

Origin of life 

Chemical reactions led to the first self-replicating molecules about four billion years ago. A half billion years later, the last common ancestor of all current life arose. The evolution of photosynthesis allowed the Sun’s energy to be harvested directly by life forms. The resultant molecular oxygen (O2) accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer (O3) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called Eukaryotes. True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized Earth’s surface. Among the earliest fossil evidence for life are microbial mat fossils found in 3.48 billion-year-old sandstone in Western Australia, biogenic graphite found in 3.7 billion-year-old rocks in Western Greenland, and remains of biotic material found in 4.1 billion-year-old rocks in Western Australia. The earliest direct evidence of life on Earth is contained in 3.45 billion-year-old Australian rocks showing fossils of microorganisms.

Do you know: Once the whole earth was covered in snow around the 1000-541 million years era. That earth was called the “snowball earth”.

Cambrian explosion(The Cambrian explosion or Cambrian radiation was an event approximately 541 million years ago in the Cambrian period when practically all major animal phyla started appearing in the fossil record. It lasted for about 13 – 25 million years and resulted in the divergence of most modern metazoan phyla. The event was accompanied by major diversifications in other groups of organisms as well.)when multicellular life forms significantly increased in complexity. Following the Cambrian explosion, 535 Million years ago, there have been at least five major mass extinctions and many minor ones. Apart from the proposed current Holocene extinction event, the most recent was 66 Million years ago, when an asteroid impact triggered the extinction of the non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, mammals, lizards and birds. Mammalian life has diversified over the past many million years, and several million years ago an African ape gained the ability to stand upright. This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which led to the evolution of humans. The development of agriculture, and then civilization, led to humans having an influence on Earth and the nature and quantity of other life forms that continues to this day. 

Composition of earth

Earth’s mass is approximately 5.97×10^24 kg (that’s a lot!). It is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%), with the remaining 1.2% consisting of trace amounts of other elements. Due to mass segregation, the core region is estimated to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.

The most common rock constituents of the crust are nearly all oxides: chlorine, sulfur, and fluorine are the important exceptions to this and their total amount in any rock is usually much less than 1%. Over 99% of the crust is composed of 11 oxides, principally silica, alumina, iron oxides, lime, magnesia, potash, and soda.

What does the future hold?

Because carbon dioxide (CO2) has a long lifespan in the atmosphere, moderate human CO2 emissions may postpone the next glacial inception by 1,00,000 years. Earth’s expected long-term future is tied to that of the Sun. Over the next 1.1 billion years, solar luminosity will increase by 10%, and over the next 3.5 billion years by 40%. Earth’s increasing surface temperature will accelerate the inorganic carbon cycle, reducing CO2 concentration to levels lethally low for plants (10 ppm for C4 photosynthesis) in approximately 100–900 million years. The lack of vegetation will result in the loss of oxygen in the atmosphere, making animal life impossible. Due to the increased luminosity, Earth’s mean temperature may reach 100 °C (212 °F) in 1.5 billion years, and all ocean water will evaporate and be lost to space within an estimated 1.6 to 3 billion years. Even if the Sun was stable, a fraction of the water in the modern oceans will descend to the mantle, due to reduced steam venting from mid-ocean ridges.

The Sun will evolve to become a red giant in about 5 billion years. Models predict that the Sun will expand to roughly 1 AU (150 million km; 93 million miles), about 250 times its present radius. Earth’s fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, Earth will move to an orbit 1.7 AU (250 million km; 160 million miles) from the Sun when the star reaches its maximum radius.

So you know what’s gonna happen next so “Live your Life to its fullest.”

Bye!! have a great time.