For life to emerge in the span of a few million years within liquid interiors of early solar system bodies, life would need to be a relatively high probability event. I don't think this changes the probability of life calculus vs the traditional life emerging on Earth story.

Unless life can only appear on that kind of environment for some reason.

It's hard to imagine any such reason. Honestly I don't think there's any to find. But it's still an open question.

No, that's wrong. You're ignoring that if it didn't happen, we wouldn't be here to see the result. Observer selection bias. The less common OoL is, the more biased our observation is.

Observer selection bias is independent of the earth vs non earth body question, it's an issue regardless.

Yes, it also demolishes the naïve Copernican argument that because life is on Earth, it must be common.

The more subtle argument was that because life originated early on Earth, OoL must be a high probability event. But that argument implicitly assumes the probability of OoL is relatively constant with time, so it wouldn't be biased to occur early. OoL on small planetesimals is naturally biased to occur early, due to decay of those short lived radioisotopes. After the planetesimals freeze OoL there doesn't seem possible.

Ok. What is an Ool?

Watch the movie Caveman to find out! Ool anyone?

In this context "Origins of life"

I would suggest replacing 'Ool' by 'origin of life' or even better just 'life' then. Is much easier to understand and it just adds one character to the term

I would think this point would be obvious, but apparently not given the many frustrating discussions I’ve had with smart people on the topic. (Maybe there is a subtlety I’m not appreciating?) It’s a relief to see the good solid sense in all your comments on this thread.

If there were enough of these warm, water-bearing bodies, then the probability could be low and still result in early life formation, right?

Especially if the "enough" is "enough around any star, anywhere". The a priori probability of it happening around any particular star need not be high. And "anywhere" can be something extremely broad, as in "on any branch of a universal Many Worlds wave function".

Yes but the window of time during which these bodies could have contained liquid water was very narrow, so there would have needed to be a very high number of such bodies to support the low probability of life hypothesis

Maybe i lack imagination but i don't see how rock formed in a deep ocean could survive relatively unchanged by the kind of impact that would launch it out into space.

Your idea fixes that for me.

Tons of assumptions, we can go hyperbolic onto almost anything if you lean into it hard enough.

Unless there is some solid proof that life happened on Earth well before larger bodies of water formed, I'd go for the most obvious theory - biggest stable body of water around and that is our pretty unique planet.

The current mass of asteroids is estimated to be about the same as the current mass of Earth's oceans. The mass of asteroids early in the solar system was likely much larger. So I don't see why one would necessarily prefer Earth to be the OoL location.

I think the current contender for biggest body of water in the solar system is Europa.

It's still a heck of a coincidence that one of these life-bearing asteroids hit Earth at exactly the time life could survive here. This becomes more likely if a lot of asteroids develop life, pushing it back into high-probability. Though it's still more susceptible to view bias, since you could have lots of stellar systems where life freezes before it makes it to a planet.

Either way, the notion of asteroids being more hospitable to OoL than planets, with their complex and varied environments and chemistry, would require quite the extraordinary evidence in my book.

Since we don't have a great idea how life originated, preferring Earth to these small bodies seems to me to be mere prejudice. This is especially the case when early Venus and Mars were likely more habitable than early Earth.

It wouldn't be necessary for a life bearing asteroid to hit Earth in order to seed Earth. Rather, a collision of a life-bearing asteroid (perhaps since frozen) in space would create a large number of fragments, any one of which could seed Earth. This strikes me as the most certain part of the scenario. After all, this is how meteorites are created.

> preferring Earth to these small bodies seems to me to be mere prejudice.

I really don't think it is. For any favorable condition you might find in asteroids, early planets can probably match it, and a bunch of other possible conditions besides, with the additional benefit of not requiring a stage where the nascent life has to survive an impact at orbital speeds, subsequent flight through cold irradiated vacuum, and then re-entry through a dense planetary atmosphere. I'm not saying it's impossible, but I'm saying it needs a lot more evidence to take it seriously.