Yay, first blog post! For the sake of manners - Hi! My name's CJ, I'm 21 years old, and I'm from Wollongong in Australia. I am currently halfway through my third year of university study, but I have almost twice as long again before I get out of uni due to my decision to pursue my Masters and PhD. How are you today? Well, I hope! I have a hundred thousand different kinds of passion for life, and, as such, I'd like to share with you in this first post what incredible luck we've had! To explain this, we're going to go on a bit of a trip over the course of several blogs, and, for the sake of doing it properly, I'm going to start this trip at the best place I can think of. At the beginning of our planet – or, specifically, the beginning after our planet was formed.
Now, I want you to remember, in the beginning, there was not darkness. There was day, and night, and heat so darn intense the bonds between our cells would literally let go and we'd disintegrate. We had a moon, which is really just a conglomeration of magmas thrown out into orbit after a MAR-SIZED object collided with the ball of molten rock that we now call home, gravity, and a very thin atmosphere composed primarily of gasses from the solar nebula such as hydrogen and helium and, eventually, as we go big enough (~40% of our current mass), managed to retain an atmosphere with other elements. Then, some 4 BILLION years ago, the earth underwent a period of intense asteroid bombardment. Now, asteroids are largely composed of two elements - hydrogen and oxygen - and they are combined in a very specific way. Two Hydrogen atoms for every Oxygen atom (H2O). Recognise that formula? You should. After all, is does compose 70% of your mass - Water! But back to that later.
Right now, we’re on the Earth, it’s hot, and we’re being utterly HAMMERED by asteroids, which not only provide additional water but cause what steam has been allowed to collect in the mantle to escape in massive volcanic eruptions and vents. This event, catastrophic as it sounds, actually allowed for life, as what is now known as the second atmosphere, a thick layer of steam and other gasses, was formed, held onto our planet by its ever increasing gravitational force. Then, the planet cooled - on the outside, at least, and this cool outer shell became what we now call the mantle. Clouds gathered as the steam cooled and it rained. For a very, very long time – about 750 million years, to be exact (Told you it was a long time!). But if you think about it, it makes sense – it takes an hour, maybe two, of constant, steady rain to make a puddle: a day to make any significant change in the water level of a lake; and a week to cause a massive flood and overflow of rivers, right? Well, these rains made the oceans. Relative speaking, it makes sense, particularly considering that there were several collisions with major bolides in this time which may well have re-evaporated the forming oceans and forced the process to restart.
What was left in the atmosphere after the formation of the oceans was probably this: ammonia, methane, carbon dioxide, nitrogen, hydrogen and trace amounts of helium as well as any remaining water vapour and the masses of tephra, ash and dust thrown up from the planet’s surface due to the ongoing bolide impacts and volcanic activity on the surface. There was no ozone layer, so ultraviolet rays would have been incredibly high, no oxygen, and the temperatures still exceeded several hundred degrees Celsius. But regardless – miraculously! - something incredible happened. Something that, to the best of our knowledge, hasn’t happened anywhere else in the universe (though, personally, I think the probability of this only happening here is minute!) – tiny bacteria, capable of living in the anoxic (oxygen-less) environment of the early oceans sprang up seemingly from out of nowhere. They were undeniably simple – single celled organisms with only one function: to reproduce, to replicate... to evolve. And evolve they did. Over the course of millions of years, and possibly hundred of millions of replication models and forms, these bacteria began to collect into prokaryotes, some of which then became the earliest plants. And with plants come another ingredient for more complex life – OXYGEN.
Plants have a remarkable ability – they take all their energy from the sun, convert this energy into simple sugars called carbohydrates, and survive on those through a process called photosynthesis. However, a by-product of this reaction, amazingly, is oxygen. So as more and more of these very simple plants (mostly algae’s) came into being, more oxygen was produced, which then proceeded to bond with Limestone, Iron and other minerals that were present in the oceans and the surrounding waterlogged areas. The result of these reactions was that the oceans turned green for some time – would have been a sight to behold but for one major problem. There was still very, very little free oxygen in the atmosphere, as, while it had other elements to bond with, the gasses produced by photosynthesis gave them preferential treatment, so the green oceans view would have been pretty for the 2 seconds you’d have survived to see them. Free atmospheric oxygen did not really begin to collect until all the reactions had stopped, and the oxygen atoms were able to escape from the oceans and collect in the atmosphere, forming the Earth’s third atmosphere. This was number one of three major impacts that the effects of photosynthesis had.
Number two was the development of the ozone layer, which sharply decreased the amount of radiation reaching the Earth’s surface, allowing for life to form on and near to the surface of the oceans for the first time and opening the door for life to move onto land.
Ironically, what opened the door for complex lifeforms to evolve shattered the fragile system of simple lifeforms that already had. The third effect was what has come to be known as the “Oxygen Catastrophe”, where much of the life on Earth at the time was completely decimated due to oxygen poisoning, with only a few resistant lifeforms surviving and thriving.
I think we’ll leave it there for this week. I should have the next chapter of our little journey posted by next Sunday. For now, here’s a little something to think on:
How do you think life developed on Earth? Was it an extra-terrestrial source such as an asteroid carrying simple lifeforms locked in it’s ice, or was life of terrestrial origin?
Let me know what you think!
Cheers!
Cheers!
- CJ
For an amazing documentary series which provides an amazing visual representation of the kinds of ideas in the blog, please go to: from the PBS-Nova series
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