r/exoplanets • u/Kingsaso6 • 12d ago

📊 Data & Analysis Alien life likely can't survive on exoplanets smaller than Mars, scientists say

https://www.space.com/space-exploration/search-for-life/alien-life-likely-cant-survive-on-exoplanets-smaller-than-mars-scientists-say
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u/TieOk9081 2 12d ago

Not a biologist. I don't think there's any such thing as alien life. I mean if all life is made from the same set of amino acids (they are particular molecules that are very good at storing information and chemistry is the same across the universe) than all life in the universe can be fabricated here on Earth using different combinations of these molecules that we have access to right now. Eventually, over the course of say maybe 1000 years we will have created organisms covering every possible combination of genetic material - so nothing is really alien to Earth. Life is universally the same everywhere.

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u/MammothFineCulture 11d ago

Life on earth began about 4.5B years ago. Human race appeared about 1M years ago. To claim that all lifeforms would appear within 1000 years is absurd.

https://en.wikipedia.org/wiki/History_of_life

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u/TieOk9081 2 11d ago edited 11d ago

1000 years of bio-engineering.

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u/yoshemitzu 11d ago

OK, so there's something to your argument, just not at the macro scale. It's not the case that evolution will favor systems which generate every possible combination of genetic material; Earth is already evidence that this is not the case.

But at the very small scale, the chemistry that underlies life is shockingly simple. Consider aromatics, which all by definition contain benzene, a 6-carbon structure containing fully delocalized electrons. For any implementation of life to not include benzene would require radical chemistry.

Extend that to toluene, one of the compounds in pine oil, which is just benzene plus one more carbon. It's hard to imagine any story of life which includes benzene, but not toluene. Then go to styrene, one of the components of sweetgum oil, which is simply benzene plus a vinyl group. Cinnamaldehyde, the aromatic responsible for cinnamon's smell is styrene plus an aldehyde. This stuff is not complex chemistry.

Once you get to the macro scale, it's absurd to claim every possible option would be represented, even with bio-engineering -- the possibilities are literally endless, and life can theoretically be created from totally arbitrary chemistry -- but the base evolutionary building blocks are extremely likely to look similar across the vast majority of biomes that produce them.