Re: Panspermia OR mystic sky Daddy
Panspermia comes in two forms:
1) Life here started out there (true panspermia)
2) Life here started because things out there delivered to earth the relevant complex chemistry during or after the late heavy bombardment (pesudo-panspermia)
The first is unknowable until we explore a lot more.
The second is highly likely, given the formation of the moon, and the damage done to the surface during the late heavy bombardment.
To the best of our knowledge, this is the history of the earth:
1) Earth accretes from the protoplanetary disk, accumulating all sorts of yummy elements.
2) Earth is whacked by Theia, a body roughly the size of mars. This completely liqufies the mantle. Heavy elements sink to the core. Silicates rise. Lots of stuff gets thrown into orbit, but not much of the really interesting stuff (like Uranium, gold, etc), because that was too heavy, and sunk to the core of the Eath.
3) The Earth resolidifies (mostly), trapping virtually all volatiles in a silicon, iron and magnesium matrix.
4) Massive volcanism is accompanied by continued bombardment from space. Carbon dioxide and methane are vented from the young planet en masse.
5) The bombardment seeds a young earth with Nitrogen, Hydrogen and more complex chemicals based upon them. (Ammonia, water, etc.) Enough falls to form the early oceans. Very little land is above sea level.
6) The planet continues cooling. Plate tectonics starts. Life arises.
7) Early carbon dioxide metabolism begins. Most oxygen absorbed by oceans, rocks.
8) The oxygen catastrophe occurs.
9) Multicellular life arises.
Panspermia here is of the "pesudo-pansermia" variety: the volatiles necessary to make things go were delivered to a young earth by comets after the big whack. Considering that fits with standard accretion theory, I don't see your beef.
It doesn't mean that the goo which became us congealed "out there" as opposed to "here". But it does mean that it's somewhat unlikely that all the chemical processes required to make every single chemical required for life arose on Earth itself.
Which, if you think about it, makes perfect sense. The various chemicals required for life all have different formation requirements. A protoplanetary disk is huge. The idea that some of these molecules formed elsewhere in the system and then found their way here after the big whack is pretty logical. I'm sure that some of the chemicals required to make it all go did form on Earth as a result of volcanism after the big whack. I'm equally sure that we needed the late heavy bombardment to seed Earth with things like nitrogen and hydrogen or we simply wouldn't be here to have this debate in the first place.
So please, do some research into "pesudo-panspermia" or "soft panspermia". It is not the same as "all life floated in from elsewhere", but it is a great metric fuck of a lot more likely than "all life started here".
Biting the hand that feeds IT
