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Comment by hydrogen7800 | Hacker News Reader

>But it seems unclear to me how the researchers would distinguish between one super-Earth and >10^10 smaller rocks?

I have a similar feeling when life on earth is suggested to be "alien", arriving via debris in the solar system as the earth formed. Isn't everything in the solar system coalesced from the same debris?

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That always felt like a deus ex machina answer to me too. We don't know exactly how abiogenesis happened on earth so some people just like to cut off the chain of causation with the idea of, "it was seeded"... but then how did abiogenesis happen elsewhere?

I don't think that's a very popular theory among anyone who knows what they're talking about though.

A hypothesis I'd seen (from the "aliens" guy, Abraham "Avi" Loeb, at Harvard) is that early in the evolution of the Universe everything was roughly in the Goldilocks zone (warm enough for liquid water, not so hot as to generate steam, not so cold as to result in ice), and ... more dense. If life more-or-less inevitably arises under such circumstances, then there's some credence to the argument that life might have arisen in many parts of the Universe, potentially hybernating in some sort of spore / inactive form, until rocky planets arose later. But we have no specific proof of this, and it seems strongly plausible that life could instead have arisen independently on individual planets and/or moons.

See this thread: <https://news.ycombinator.com/item?id=37850997>.

From which:

Kurzgesagt did a video on the concept: <https://www.youtube.com/watch?v=JOiGEI9pQBs>.

Avi Loeb, "The habitable epoch of the early Universe". International Journal of Astrobiology, vol. 13, 4."

<https://www.cambridge.org/core/journals/international-journa...>

Well if we found current or fossil life with a common ancestor on other bodies it would certainly demonstrate that it arrived via debris; whereas if we find life with no common ancestor or find no evidence of life at all that would reject the hypothesis. It wouldn't necessarily answer which body was the original birthplace, but for the purposes of modelling, whether life happened to start here is a much less impactful question than whether life had to start here. If all life here started here, then life had to develop quickly; if we could potentially descend from stuff in the pre-solar system debris field that could add billions of years to the clock, and makes interstellar panspermia highly plausible.

Same thing with people who naively believe that amino acids can only be formed in space and can only be brought to Earth in asteroids, as opposed to forming *ON* Earth.

Our current best guess is a geothermal vent in a high phosphorus 'soda lake' like the one in Canada. https://www.science.org/content/article/unusual-soda-lakes-m...

The life-bearing debris would have to arrive quite some time after formation of Earth, as it was molten. Surviving atmospheric entry is hard, surviving after landing in lava is impossible.

I was going to expand on my comment about the difference between alien and non-alien being a difference only in time. It's all from the same stuff.

It makes a difference to our understanding of the conditions under which life can form.

If life-bearing debris exists, it would surely be floating around the galaxy forever.

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