3 ms·

The most likely scenario is that it would be microbes, but even microbes would be pretty amazing if they turned out to be based on something other than DNA/RNA

by jl6 3y ago

The most likely scenario is that it would be microbes, but even microbes would be pretty amazing if they turned out to be based on something other than DNA/RNA or proved sufficiently distinct from Earth life to suggest a second abiogenesis event.

tessierashpool 3y ago
it's more interesting if they're not that different from Earth life. many species of fungi, bacteria, and lichen can survive in space. it's not just tardigrades. they're not a fluke; they're part of a pattern. I think it's extremely likely that we'll not only find life is very common, but that many species found on earth are also found on other planets.
- jvm___ 3y ago
  Rocks and dust, from what we've seen so far are governed by the same rules of physics for their size and composition. Will life obey the same rules?
- empyrrhicist 3y ago
  Species? Surely they would diverge over the timescales involved...
  - tessierashpool 3y ago
    species is probably the wrong word. maybe genus or phylum. apologies for the rusty biology. but sharks have been sharks for 400 to 450 million years. I'm sure sharks are terrestrial in origin, but that's an intergalactic timescale during which very little evolutionary change occurred, or was necessary, for a particular category of creature. maybe tardigrades have been tardigrades for 450 million years too.
  - keepamovin 3y ago
    And maybe evolve into the dominant life or civilization. It may turn out that upright bipedal “5 star” form is very conserved in advanced civilizations. So maybe you have the Lion people planet, the lizard people planet, the wolf people planet. We are the chimp people planet haha :)
    - Tao3300 3y ago
      We're the lizard people planet that appears to be a chimp people planet.
      - spacecadet 3y ago
        lol but why trade being lizard people for chimp people? are we ashamed?
      - midoridensha 3y ago
        No, we're the chimp people planet that's been taken over by disguised invaders from the lizard people planet. They even made a TV show about this back in the 1980s, called "V".
        Tao3300 3y ago
        Exactly
        keepamovin 3y ago
        Hahaha. Maybe, maybe. But what if (at least some of) the lizard people are actually not from another planet but are from an alternate timeline dimension of Earth where the Cretaceous-Paleogene extinction event didn't happen and it was reptiles that evolved into a "humanoid" 5 pointed upright form? o_O
gus_massa 3y ago
Nobody is sure, but my guess is that perhaps DNA and RNA are inevitable, because perhaps they are the best/easiest solution for the problem. Even proteins and amino acids are probably inevitable, but there are more variants here. The interesting part to detect a second abiogenesis event is the translation table from DNA to amino acids https://en.wikipedia.org/wiki/Genetic_code https://en.wikipedia.org/wiki/Genetic_code It's almost blocked, but as far as we know, the blocks are random. And there are even a few small variants here on Earth, that suggest in a second abiogenesis event it would work with a different randomization. I wrote a comment with more details a long time ago https://news.ycombinator.com/item?id=34229988 https://news.ycombinator.com/item?id=34229988 Self nitpicking: The DNA could be twisted in the oposite direction. As far as we know it should work if you have the "mirrored" version of all the helper proteins and stuff. This could be a strong evidence of a second abiogenesis event.
- hoseja 3y ago
  They are certainly not. Open your imagination.
  - gus_massa 3y ago
    It's not clear that the only option is DNA, but we will not know until we find a few independent live origins. Anyway, even if there is a unknown biology law that says that DNA and proteins are inevitable and that confuses us when we detect a second planet with life, if they have an independent origin there is absolutely no way that they have a "genetic code" that can be confusing.
- civilitty 3y ago
  Some form of DNA, RNA, and proteins are all technically inevitable because they're just polymers built up of standard monomers just like complex carbohydrates, fiber, plastics, waxes, etc. It's just an accident of history that carbon based life on earth settled on the specific nucleotides and amino acids. What's likely to be the most different is the transcription and translation machinery. On the nucleotide side there are synthetic creations like Hachimoji DNA [1] and xDNA [2] and a grand total of over 500 (!) amino acids have been found in nature but only 22 are encoded in DNA. IIRC it's mostly a question of the initial conditions on Earth, specifically the acidity and temperature that decides the possible chemistry available to evolving life. [1] https://en.wikipedia.org/wiki/Hachimoji_DNA https://en.wikipedia.org/wiki/Hachimoji_DNA [2] https://en.wikipedia.org/wiki/XDNA https://en.wikipedia.org/wiki/XDNA
BurningFrog 3y ago
If there are microbes on/in Europa, I think they're most likely from Earth. You just need one rock with live microbes to splash into the Europa ocean, and over 4 billion years, many such rocks must have been knocked off Earth.
- cmrdporcupine 3y ago
  Between here and there is... a lot of cold, vacuum, and extremely intense radiation. I'd be surprised if anything that evolved here could survive the trip.
  - fbdab103 3y ago
    Tardigrades can survive in space[0]. > In September last year, a team of scientists launched a squad of tiny animals into space aboard a Russian satellite. Once in orbit, the creatures were shunted into ventilated containers that exposed them to the vacuum of space. In this final frontier, they had no air and they were subjected to extreme dehydration, freezing temperatures, weightlessness and lashings of both cosmic and solar radiation. It’s hard to imagine a more inhospitable environment for life but not only did the critters survive, they managed to reproduce on their return to Earth. [0] https://www.nationalgeographic.com/science/article/tardigrades-become-first-animals-to-survive-vacuum-of-space https://www.nationalgeographic.com/science/article/tardigrad...
    - cmrdporcupine 3y ago
      Yes, but. https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Jupiter_s_radiation_belts_and_how_to_survive_them https://www.esa.int/Enabling_Support/Space_Engineering_Techn... The radiation around Jupiter is... really crazy. Like, not around-orbit-of-earth crazy, way worse.
      - tessierashpool 3y ago
        Deinococcus radiodurans has enough radiation resistance to handle the trip from Mars to Earth (or vice versa). And that's just one we know about. We are very, very far from having ever performed an exhaustive catalog of all bacterial species, let alone one which determined the full range of bacterial radiation resistance.

by jl6 3y ago

tessierashpool 3y ago

it's more interesting if they're not that different from Earth life. many species of fungi, bacteria, and lichen can survive in space. it's not just tardigrades. they're not a fluke; they're part of a pattern. I think it's extremely likely that we'll not only find life is very common, but that many species found on earth are also found on other planets.

jvm___ 3y ago
Rocks and dust, from what we've seen so far are governed by the same rules of physics for their size and composition. Will life obey the same rules?
empyrrhicist 3y ago
Species? Surely they would diverge over the timescales involved...
- tessierashpool 3y ago
  species is probably the wrong word. maybe genus or phylum. apologies for the rusty biology. but sharks have been sharks for 400 to 450 million years. I'm sure sharks are terrestrial in origin, but that's an intergalactic timescale during which very little evolutionary change occurred, or was necessary, for a particular category of creature. maybe tardigrades have been tardigrades for 450 million years too.
- keepamovin 3y ago
  And maybe evolve into the dominant life or civilization. It may turn out that upright bipedal “5 star” form is very conserved in advanced civilizations. So maybe you have the Lion people planet, the lizard people planet, the wolf people planet. We are the chimp people planet haha :)
  - Tao3300 3y ago
    We're the lizard people planet that appears to be a chimp people planet.
    - spacecadet 3y ago
      lol but why trade being lizard people for chimp people? are we ashamed?
    - midoridensha 3y ago
      No, we're the chimp people planet that's been taken over by disguised invaders from the lizard people planet. They even made a TV show about this back in the 1980s, called "V".
      - Tao3300 3y ago
        Exactly
        keepamovin 3y ago
        Hahaha. Maybe, maybe. But what if (at least some of) the lizard people are actually not from another planet but are from an alternate timeline dimension of Earth where the Cretaceous-Paleogene extinction event didn't happen and it was reptiles that evolved into a "humanoid" 5 pointed upright form? o_O

gus_massa 3y ago

Nobody is sure, but my guess is that perhaps DNA and RNA are inevitable, because perhaps they are the best/easiest solution for the problem. Even proteins and amino acids are probably inevitable, but there are more variants here. The interesting part to detect a second abiogenesis event is the translation table from DNA to amino acids https://en.wikipedia.org/wiki/Genetic_code https://en.wikipedia.org/wiki/Genetic_code It's almost blocked, but as far as we know, the blocks are random. And there are even a few small variants here on Earth, that suggest in a second abiogenesis event it would work with a different randomization. I wrote a comment with more details a long time ago https://news.ycombinator.com/item?id=34229988 https://news.ycombinator.com/item?id=34229988 Self nitpicking: The DNA could be twisted in the oposite direction. As far as we know it should work if you have the "mirrored" version of all the helper proteins and stuff. This could be a strong evidence of a second abiogenesis event.

hoseja 3y ago
They are certainly not. Open your imagination.
- gus_massa 3y ago
  It's not clear that the only option is DNA, but we will not know until we find a few independent live origins. Anyway, even if there is a unknown biology law that says that DNA and proteins are inevitable and that confuses us when we detect a second planet with life, if they have an independent origin there is absolutely no way that they have a "genetic code" that can be confusing.
civilitty 3y ago
Some form of DNA, RNA, and proteins are all technically inevitable because they're just polymers built up of standard monomers just like complex carbohydrates, fiber, plastics, waxes, etc. It's just an accident of history that carbon based life on earth settled on the specific nucleotides and amino acids. What's likely to be the most different is the transcription and translation machinery. On the nucleotide side there are synthetic creations like Hachimoji DNA [1] and xDNA [2] and a grand total of over 500 (!) amino acids have been found in nature but only 22 are encoded in DNA. IIRC it's mostly a question of the initial conditions on Earth, specifically the acidity and temperature that decides the possible chemistry available to evolving life. [1] https://en.wikipedia.org/wiki/Hachimoji_DNA https://en.wikipedia.org/wiki/Hachimoji_DNA [2] https://en.wikipedia.org/wiki/XDNA https://en.wikipedia.org/wiki/XDNA

BurningFrog 3y ago

If there are microbes on/in Europa, I think they're most likely from Earth. You just need one rock with live microbes to splash into the Europa ocean, and over 4 billion years, many such rocks must have been knocked off Earth.

cmrdporcupine 3y ago
Between here and there is... a lot of cold, vacuum, and extremely intense radiation. I'd be surprised if anything that evolved here could survive the trip.
- fbdab103 3y ago
  Tardigrades can survive in space[0]. > In September last year, a team of scientists launched a squad of tiny animals into space aboard a Russian satellite. Once in orbit, the creatures were shunted into ventilated containers that exposed them to the vacuum of space. In this final frontier, they had no air and they were subjected to extreme dehydration, freezing temperatures, weightlessness and lashings of both cosmic and solar radiation. It’s hard to imagine a more inhospitable environment for life but not only did the critters survive, they managed to reproduce on their return to Earth. [0] https://www.nationalgeographic.com/science/article/tardigrades-become-first-animals-to-survive-vacuum-of-space https://www.nationalgeographic.com/science/article/tardigrad...
  - cmrdporcupine 3y ago
    Yes, but. https://www.esa.int/Enabling_Support/Space_Engineering_Technology/Jupiter_s_radiation_belts_and_how_to_survive_them https://www.esa.int/Enabling_Support/Space_Engineering_Techn... The radiation around Jupiter is... really crazy. Like, not around-orbit-of-earth crazy, way worse.
    - tessierashpool 3y ago
      Deinococcus radiodurans has enough radiation resistance to handle the trip from Mars to Earth (or vice versa). And that's just one we know about. We are very, very far from having ever performed an exhaustive catalog of all bacterial species, let alone one which determined the full range of bacterial radiation resistance.