...come from out there? The "Starseed" theory is something which has been debated - and no, it doesn't involve intelligent aliens. At least not the version seriously considered by scientists.
The version seriously considered doesn't even involve microbes. It involves the precursor molecules for life being dropped on Earth by meteorites. In just the right conditions, they rapidly create RNA - which then becomes DNA and thus our kind of life.
If this is true, then it makes it more likely that extraterrestrial life will be based on DNA or something similar - good news if we ever want to expand beyond this planet (although bad news if worried about biocontamination).
The alternative is that life started spontaneously near hydrothermal vents.
Here's one thought, though:
Does one of these actually prevent the other?
I would argue that RNA forming in ponds hit by meteors and RNA forming by hydrothermal vents don't cancel each other out and an even more intriguing possibility is life starting by both methods and then combining. If both methods happened to produce the same chemicals, then we would never know.
Or did life, even at the start, compete with each other and are we descended from the winner?
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