Life is something we take for granted, I do it myself as well. We live on a planet with such great diversity. Earth has multiple continents, climates, and the most amazing forms of life live on it. In this series, I want to take you on a journey. The journey of the evolution of the earth and life that lives on it. So we start at the beginning, the creation of the earth. We must travel almost 5 billion years back in time to see what caused the creation of our planet.
Off course, we cannot know for sure how Earth was created, but I will stick to the most accepted theories.
Core accretion model:
A newborn star, our own sun, is completely surrounded by dust. Planets, including earth are nowhere to be found. The tiny dust particles start to cling together by themselves because of electrostatic charges. This keeps on going until a rock of half a mile in diameter is created. This is big enough for a rock to have its own gravity in space. This attracts more rocks, eventually creating the earth (figure 1).
Figure 1. Core accretion model.
But 4,5 billion years ago, the earth looks nothing like we know it today. The surface is around 1,093 degrees Celsius (2000 degrees Fahrenheit). There is no atmosphere or air, just carbon dioxide, nitrogen, and water vapor. Earth is a giant ball of liquid boiling rock, an endless ocean of lava. Earth’s core forms first, because the heavy elements, mostly Iron and Nickel, sink towards the center. The lighter elements sink less far and thus created a layer on top of the Iron and Nickel layer, and so on. This created the layers of the earth that we have now, as well as our gravitational field.
Creation of the moon:
Millions of years pass on, until another planet, Theia, around the same size of Mars, is headed straight for Earth. The planet travels with a speed of 10 miles per second. The two planets collide, destroying the smaller one, Theia, completely. Earth is hit with enough force to tilt Earth’s orbital plane by 23 degrees. It shoots billions of tons of Earth's crust and mantel into space. This debris started orbiting around the Earth, like the rings you see orbiting Saturn currently. Again, the rocks cling together, slowly creating a ball again, big enough to have its own gravity, pulling more debris towards it. Within a few thousand years, this quickly formed wat we now know as the moon (figure 2).
Figure 2. Schematic images of the formation of our moon.
Time passes on, and space around the earth is at a constant -268 degrees Celsius (-450 degrees Fahrenheit), while the earth is still a ball of liquid rock. Space cools off the surface of the earth from the outside inwards. This creates the earth's crust.
Water and land:
We fast forward until 4.2 billion years ago. Leftover from the formation of the solar system, debris starts raining down on earth with an astounding rate. Constant meteors are hailing down. But inside these meteors, is perhaps the most vital aspect of life as we know it. Inside are crystals that look like grains of salt, and inside the crystals are miniscule droplets of water (figure 3). When a meteor crashes down on Earth, water is released out of the crystals, leaving it on Earth’s crust. The number of meteors falling down is enough to form pools on the Earth. Still, meteors keep falling, releasing more and more droplets of water. Eventually oceans form, and the number of meteors decreases. Earth starts to look like the Earth as we know it.
Figure 3. Photograph of a fluid inclusion in the Monahans meteorite. V indicates a small bubble (composed of H2O); L indicates liquid salty water. Bubbles are rare in the inclusions, indicating a formation temperature of the fluids of less than 100 degrees Celsius.
But volcanoes are still erupting, because below the crust, Earth is still a liquid chaos. Erupting volcanoes causes land to push upwards, reaching above water level, creating islands bigger and bigger. Now, the basis is formed for the origin of life. In the next episode, we will dive into the oceans, where life started.
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Sources:
National geographic's 'the story of the earth'.
National geographic's 'creation of the earth'.
https://www.space.com/19175-how-was-earth-formed.html
Image sources:
https://www.pinterest.co.uk/pin/317574211199649783/
https://pt.slideshare.net/mj_d/6-terra-planetastelricos
http://www.astro-photography.net/Formation-of-the-Moon.html
http://www.psrd.hawaii.edu/Nov99/PurpleSalt.html