Day 76: The Eons

So I had a question: What was the atmosphere like when the asteroid hit all those years ago? I mean, how did the air feel? How did the air feel when the dinosaurs were alive? ‘Cause, how is it that the atmosphere led to such creatures being created? I mean, we were created recently and this is what the flora and fauna is like.

I guess, I got that question because I realized I have a vague idea of the animals of the time but no idea about the atmosphere that made it possible.

So let’s start at the very beginning, the Hadean Eon: Hadean is the earliest eon, it marks the moment the planet was created 4.5 billion years ago and about 500 million years after the fact. The atmosphere then was the most hostile of the three main atmsopheres that the planet has experienced throughout its lifetime. Temperatures of 230 ℃ going up to 500℃ during asteroid impacts, heavy atmospheric pressures of 27 atmospheres, nebular climates with frequent volcanic eruptions mark this eon. Oceans did exist despite the extreme temperatures because the atmospheric pressure was so high, and the Moon likely formed then as well.

Then came the Archaen Eon. Despite it not having the most hospitable atmosphere, it did give rise to prokaryote life early on. Mainly filled with volcanic and greenhouse gases, the temperatures were in fact moderate. But the atmosphere is believed to have had less than 0.001% of free oxygen that we have today, some studies indicating way less than that.

Now let’s venture into more complex life forms, the Proterozoic Eon and after.