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Asked by Molly to Cristiane, Nikolai, Richard, Samuel on 18 Mar 2015. This question was also asked by Emmmaaaa.
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Samuel Ellis answered on 18 Mar 2015:
There are 2 main scientific schools of thought when it comes to the origin of life.
The first is that life developed spontaneously on Earth a very long time ago through chemistry. This theory is that chemical reactions randomly made some of the basic molecules needed for life, which eventually joined together in a way which made the first simple microbial life forms.
The other idea is that life came from outer space. The thinking is that either microscopic life forms, or even just key organic molecules needed for life forming, may have come to our planet on meteoroids or asteroids. If this is possible, then life could maybe exist in lots of other places spread by objects in space too.
Obviously this all had to happen many billions of years ago, so it is very difficult to prove either option!
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Nikolai Adamski answered on 18 Mar 2015:
Sam has nicely laid out the two main theories on that question.
Let me add that scientists have done experiments simulating the impact of an asteroid on earth. On impact, enormous amounts of energy are released. In their simulations, scientists seem to have discovered that complex molecules could form after the impact (when there was still a lot of energy left). These complex molecules are thought to have been essential for life.
So life on earth seemed to have needed a kick start from an asteroid. But as Sam says, this is all hard to prove.
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