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Based on the developments in exo-planet research along with discoveries like this over the past couple of years, I would conjecture that life is ridiculously co

Based on the developments in exo-planet research along with discoveries like this over the past couple of years, I would conjecture that life is ridiculously common. But by life, I mean microbial life. I would imagine that multi-cellular life is much rarer, and life capable of reaching human-level intelligence and beyond is probably absurdly rare, on the level of something like one species per galaxy. It's all worthless conjecture, of course, but the point is I wouldn't be surprised if microbial life is very, very common.

Retric 10y ago
On earth the jump from single celled life to multi celled life was very rapid relative to how long planets can probably support life on average. The first evidence of multicellularity is from cyanobacteria-like organisms that lived 3–3.5 billion years ago.[5] https://en.m.wikipedia.org/wiki/Multicellular_organism https://en.m.wikipedia.org/wiki/Multicellular_organism Now this is a Biofilms ala mats of multi celled organisms so it's hard to draw a clear line based on the fossils. Other contenders are much younger, but even if you use sexual reproduction as the benchmark that's still within the first 3 billion years and earth likely has another 1.75 billion to 3.25 billion years before it gets to hot.
nostrademons 10y ago
I'm kinda curious if there's any evidence that would support or rule out intelligent life having existed on earth before. I mean, if humanity goes extinct and it's another 65 million years before another intelligent species evolves, what evidence would they have of our existence? All our buildings would've long since crumbled into dust or been crushed by plate tectonics. Metal will corrode and rust away after a few thousand years. Our largest stone monuments will be gone after 10,000 or so. You'll find occasional fossilized skeletons, but all that would tell future species is that a bipedal mammal with a large brain once existed. Even plastics, the bane of environmentalists, degrade over a couple thousand years. Probably the only thing we'd see would be a huge mass extinction and an unusually rapid change in the earth's climate. Which we've seen several times in the geologic record already.
- herbstein 10y ago
  Isaac Arthur has a very interesting video that touches on that specific topic, but with a space exploration angle. https://www.youtube.com/watch?v=k7fLNvpl0c8 https://www.youtube.com/watch?v=k7fLNvpl0c8
  - Ataraxy 10y ago
    My favorite youtube channel out in the wild! His videos are such a treat every week.
  - nikolasavic 10y ago
    I love his channel! I'm surprised it isn't more popular, it has top notch content and regularly scheduled releases.
  - leonroy 10y ago
    That was incredibly good. Some of the ethical and practical implications raised in that video by humans actually achieving interstellar travel were pretty eye opening.
- ddinh 10y ago
  What about space artifacts? Out in the vacuum stuff corrodes/degrades much slower - would satellites still be around or would they have had their orbits degraded and burned up in the atmosphere? Also, how detectable would the stuff we've left behind on Moon (the mirror, perhaps? Only thing that can probably destroy evidence of our presence on the moon would be asteroid impacts) be to a civilization that doesn't know it's there?
  - nostrademons 10y ago
    Most satellite orbits should decay and burn up in the atmosphere long before a few million years has passed. Most of the near-earth orbits become unstable within decades, and the ones that don't are subject to gravitational perturbations from the moon and other planets. The stuff on the moon will remain there for a very very long time, but until another civilization acquires the technological capability to explore a good amount of the moon's surface, it's doubtful they would stumble across the exact same spot as the Apollo landings.
moomin 10y ago
I'd guess that microbial life would evolve into cellular life almost anywhere there was enough heat.
- blacksmith_tb 10y ago
  Multicellular? Most organisms on earth are unicellular[1] even now. My impression is that multicellular organisms evolved because the 'easy' evolutionary niches were already occupied by single-celled species, and it took new tricks to compete for new niches. 1:https://www.quora.com/What-is-the-biomass-of-bacteria-What-is-the-estimated-percentage-of-bacteria-species-that-have-been-identified https://www.quora.com/What-is-the-biomass-of-bacteria-What-i...
  - theparanoid 10y ago
    It's not known exactly how multicellular life came to be. It's happened only once in the history of the earth. Nuclear dna is from Archaea and Mitochondrial dna is from bateria. Lynn Margulis was the first to propose and substantiate symbiogenesis for this.
- Symmetry 10y ago
  You need more than heat for life to evolve. You also need a source of useful energy. Probably a long-lasting chemical gradient like you see in undersea vents but there are a number of possibilities. Life has evolved on Earth to use other sources of energy too, most commonly sunlight, but the machinery to use those is much more complex.
ars 10y ago
> Based on the developments in exo-planet research along with discoveries like this over the past couple of years, I would conjecture that life is ridiculously common. In that case you must not ignore the corollary: If there is no life on those moons, then it must follow that life is ridiculously rare. And in that case, then it's pretty likely we are indeed alone in the universe.
- andrewflnr 10y ago
  (Life on enceladus -> Life is common) does not entail (No life on enceladus -> Life is rare) by any length of proof, much less one short enough to let you call it a "corollary" with a straight face. This would be so even if "Life is common" and "Life is rare" were perfect logical complements, rather than being endpoints on a wide spectrum.
komali2 10y ago
I dunno man, the galaxy alone is pretty darn big.
guelo 10y ago
That is bad conjecture. We have no evidence of life anywhere besides earth, microbial or otherwise. Exoplanet research and this new data has found planets that could conceivably host life, but that's it.
- Symmetry 10y ago
  Well, we do have evidence of past life on Mars - just not conclusive evidence. See https://en.wikipedia.org/wiki/Allan_Hills_84001 https://en.wikipedia.org/wiki/Allan_Hills_84001 and https://en.wikipedia.org/wiki/Microbially_induced_sedimentary_structure https://en.wikipedia.org/wiki/Microbially_induced_sedimentar... And, of course, that's not evidence that there's still life on Mars.
- deleted 10y ago
  [deleted]
Grue3 10y ago
Why would life be ridiculously common? It cannot appear by itself, that would be "spontaneous generation" [1], a long rejected theory. The Earth is extremely suitable for life. It could've easily supported independently evolved life-forms. Yet every living thing we know has a common ancestor, including extinct organisms. Just based on that fact, the odds are firmly stacked against other life anywhere near us. The fact that we can observe life on Earth is just a consequence of Anthropic principle [2] and says nothing about the probability of life emerging on other planets. [1] https://en.wikipedia.org/wiki/Spontaneous_generation https://en.wikipedia.org/wiki/Spontaneous_generation [2] https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle
- rnet85 10y ago
  Spontaneous generation was never a valid scientific theory. For a more accurate one look at https://en.wikipedia.org/wiki/Abiogenesis https://en.wikipedia.org/wiki/Abiogenesis Also, the probablity of generation of organic compounds which are precursors to life is pretty high given right environment, https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment
otempomores 10y ago
I think addhoc multicellular life could be very comon too
fauria 10y ago
I don't think it's a worthless conjecture. A couple days ago I submitted a link to the Great Filter article on Wikipedia https://news.ycombinator.com/item?id=14095912 https://news.ycombinator.com/item?id=14095912 It basically proposes a theory where life, being very common in the universe, eventually reaches a point (filter) that prevents it from stepping up in the Kardashov scale: http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-content/uploads/2014/05/Great-Filter1.png http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-c... You are simply putting ourselves beyond the Great Filter, although finding life in Enceladus could drastically affect that: http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-content/uploads/2014/05/Great-Filter-RARE1-1024x538.png http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-c... More info on this topic: https://news.ycombinator.com/item?id=14113461 https://news.ycombinator.com/item?id=14113461
nnq 10y ago
What intuition makes you believe that once you have microbial live + some kind of stability (low levels of ionizing radiation + a decent level of chemical stability, so not too hot), evolution to advanced multicellular organisms is not pretty much the default? I'd be more or less inclined to believe that once you have the first microbes advanced enough to support cell2cell signaling, and some kind of "condensed blueprint information mechanism" (what DNA is on Earth), the rest of the ring would pretty much be unavoidable, though slow. Human-level intelligence might be rarer, in that you'd probably need a quite few evolutions to plateau + extinction cycles (think cambrian extinction, dinosaurs' extinction and probably a few others), most likely more than we had on Earth (I's assume we kind of got lucky), probably since what you get to something like "monkey level intelligence", most increases in intelligence would be disadvantageous for survival, unless they happen in a species with a tool-usage-friendly body plan + some pack/social tendency + environment change to challenge them to evolve but not to extinct + "construction friendly solid-ish environment" (I imagine dolphins, squids and octopuses, and most monkeys plateaued because they lacked at least one ingredient of the magic combination, and this tends to be the rule...), but this should pretty much happen. And then you have the fact that our galaxy should have a few billions or tens of billions of Earth like planets based on what we know (probably more "life friendly" planets if you allow that other chemistries than "carbon + liquid water" could support life), it's pretty much unavoidable that there are quite a few human level species in the gallaxy. The scary bit it that there should be quite a few above that, that probably went past their first singularity/transcendence event and are no longer constrained by biology and individual mortality and probably dumped their biological bodies long ago... scary being the fact that we don't see any sign of their presence.
- Symmetry 10y ago
  The problem is that basic microbes only resperate over their surfaces so they have big square/cubed law limits on how large they can be and, by extension, on how complex their genomes can be. You need a hopeful monster that can run its metabolism throughout the cell to develop large genomes of the type that can support differentiated cells in multi-cellular creatures.
  - 10y ago
cJ0th 10y ago
On a related note, there has been an interesting episode of BBC's CrowdScience. They reported that robots which go to Mars (to find out about microbial life) have to go through an extreme cleaning process to make sure that they contaminate Mars as little as possible with microbial life from our planet . http://www.bbc.co.uk/programmes/p04nmxzl http://www.bbc.co.uk/programmes/p04nmxzl

Retric 10y ago

On earth the jump from single celled life to multi celled life was very rapid relative to how long planets can probably support life on average. The first evidence of multicellularity is from cyanobacteria-like organisms that lived 3–3.5 billion years ago.[5] https://en.m.wikipedia.org/wiki/Multicellular_organism https://en.m.wikipedia.org/wiki/Multicellular_organism Now this is a Biofilms ala mats of multi celled organisms so it's hard to draw a clear line based on the fossils. Other contenders are much younger, but even if you use sexual reproduction as the benchmark that's still within the first 3 billion years and earth likely has another 1.75 billion to 3.25 billion years before it gets to hot.

nostrademons 10y ago

I'm kinda curious if there's any evidence that would support or rule out intelligent life having existed on earth before. I mean, if humanity goes extinct and it's another 65 million years before another intelligent species evolves, what evidence would they have of our existence? All our buildings would've long since crumbled into dust or been crushed by plate tectonics. Metal will corrode and rust away after a few thousand years. Our largest stone monuments will be gone after 10,000 or so. You'll find occasional fossilized skeletons, but all that would tell future species is that a bipedal mammal with a large brain once existed. Even plastics, the bane of environmentalists, degrade over a couple thousand years. Probably the only thing we'd see would be a huge mass extinction and an unusually rapid change in the earth's climate. Which we've seen several times in the geologic record already.

herbstein 10y ago
Isaac Arthur has a very interesting video that touches on that specific topic, but with a space exploration angle. https://www.youtube.com/watch?v=k7fLNvpl0c8 https://www.youtube.com/watch?v=k7fLNvpl0c8
- Ataraxy 10y ago
  My favorite youtube channel out in the wild! His videos are such a treat every week.
- nikolasavic 10y ago
  I love his channel! I'm surprised it isn't more popular, it has top notch content and regularly scheduled releases.
- leonroy 10y ago
  That was incredibly good. Some of the ethical and practical implications raised in that video by humans actually achieving interstellar travel were pretty eye opening.
ddinh 10y ago
What about space artifacts? Out in the vacuum stuff corrodes/degrades much slower - would satellites still be around or would they have had their orbits degraded and burned up in the atmosphere? Also, how detectable would the stuff we've left behind on Moon (the mirror, perhaps? Only thing that can probably destroy evidence of our presence on the moon would be asteroid impacts) be to a civilization that doesn't know it's there?
- nostrademons 10y ago
  Most satellite orbits should decay and burn up in the atmosphere long before a few million years has passed. Most of the near-earth orbits become unstable within decades, and the ones that don't are subject to gravitational perturbations from the moon and other planets. The stuff on the moon will remain there for a very very long time, but until another civilization acquires the technological capability to explore a good amount of the moon's surface, it's doubtful they would stumble across the exact same spot as the Apollo landings.

moomin 10y ago

I'd guess that microbial life would evolve into cellular life almost anywhere there was enough heat.

blacksmith_tb 10y ago
Multicellular? Most organisms on earth are unicellular[1] even now. My impression is that multicellular organisms evolved because the 'easy' evolutionary niches were already occupied by single-celled species, and it took new tricks to compete for new niches. 1:https://www.quora.com/What-is-the-biomass-of-bacteria-What-is-the-estimated-percentage-of-bacteria-species-that-have-been-identified https://www.quora.com/What-is-the-biomass-of-bacteria-What-i...
- theparanoid 10y ago
  It's not known exactly how multicellular life came to be. It's happened only once in the history of the earth. Nuclear dna is from Archaea and Mitochondrial dna is from bateria. Lynn Margulis was the first to propose and substantiate symbiogenesis for this.
Symmetry 10y ago
You need more than heat for life to evolve. You also need a source of useful energy. Probably a long-lasting chemical gradient like you see in undersea vents but there are a number of possibilities. Life has evolved on Earth to use other sources of energy too, most commonly sunlight, but the machinery to use those is much more complex.

ars 10y ago

> Based on the developments in exo-planet research along with discoveries like this over the past couple of years, I would conjecture that life is ridiculously common. In that case you must not ignore the corollary: If there is no life on those moons, then it must follow that life is ridiculously rare. And in that case, then it's pretty likely we are indeed alone in the universe.

andrewflnr 10y ago
(Life on enceladus -> Life is common) does not entail (No life on enceladus -> Life is rare) by any length of proof, much less one short enough to let you call it a "corollary" with a straight face. This would be so even if "Life is common" and "Life is rare" were perfect logical complements, rather than being endpoints on a wide spectrum.

komali2 10y ago

I dunno man, the galaxy alone is pretty darn big.

guelo 10y ago

That is bad conjecture. We have no evidence of life anywhere besides earth, microbial or otherwise. Exoplanet research and this new data has found planets that could conceivably host life, but that's it.

Symmetry 10y ago
Well, we do have evidence of past life on Mars - just not conclusive evidence. See https://en.wikipedia.org/wiki/Allan_Hills_84001 https://en.wikipedia.org/wiki/Allan_Hills_84001 and https://en.wikipedia.org/wiki/Microbially_induced_sedimentary_structure https://en.wikipedia.org/wiki/Microbially_induced_sedimentar... And, of course, that's not evidence that there's still life on Mars.
deleted 10y ago
[deleted]

Grue3 10y ago

Why would life be ridiculously common? It cannot appear by itself, that would be "spontaneous generation" [1], a long rejected theory. The Earth is extremely suitable for life. It could've easily supported independently evolved life-forms. Yet every living thing we know has a common ancestor, including extinct organisms. Just based on that fact, the odds are firmly stacked against other life anywhere near us. The fact that we can observe life on Earth is just a consequence of Anthropic principle [2] and says nothing about the probability of life emerging on other planets. [1] https://en.wikipedia.org/wiki/Spontaneous_generation https://en.wikipedia.org/wiki/Spontaneous_generation [2] https://en.wikipedia.org/wiki/Anthropic_principle https://en.wikipedia.org/wiki/Anthropic_principle

rnet85 10y ago
Spontaneous generation was never a valid scientific theory. For a more accurate one look at https://en.wikipedia.org/wiki/Abiogenesis https://en.wikipedia.org/wiki/Abiogenesis Also, the probablity of generation of organic compounds which are precursors to life is pretty high given right environment, https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment

otempomores 10y ago

I think addhoc multicellular life could be very comon too

fauria 10y ago

I don't think it's a worthless conjecture. A couple days ago I submitted a link to the Great Filter article on Wikipedia https://news.ycombinator.com/item?id=14095912 https://news.ycombinator.com/item?id=14095912 It basically proposes a theory where life, being very common in the universe, eventually reaches a point (filter) that prevents it from stepping up in the Kardashov scale: http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-content/uploads/2014/05/Great-Filter1.png http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-c... You are simply putting ourselves beyond the Great Filter, although finding life in Enceladus could drastically affect that: http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-content/uploads/2014/05/Great-Filter-RARE1-1024x538.png http://28oa9i1t08037ue3m1l0i861.wpengine.netdna-cdn.com/wp-c... More info on this topic: https://news.ycombinator.com/item?id=14113461 https://news.ycombinator.com/item?id=14113461

nnq 10y ago

What intuition makes you believe that once you have microbial live + some kind of stability (low levels of ionizing radiation + a decent level of chemical stability, so not too hot), evolution to advanced multicellular organisms is not pretty much the default? I'd be more or less inclined to believe that once you have the first microbes advanced enough to support cell2cell signaling, and some kind of "condensed blueprint information mechanism" (what DNA is on Earth), the rest of the ring would pretty much be unavoidable, though slow. Human-level intelligence might be rarer, in that you'd probably need a quite few evolutions to plateau + extinction cycles (think cambrian extinction, dinosaurs' extinction and probably a few others), most likely more than we had on Earth (I's assume we kind of got lucky), probably since what you get to something like "monkey level intelligence", most increases in intelligence would be disadvantageous for survival, unless they happen in a species with a tool-usage-friendly body plan + some pack/social tendency + environment change to challenge them to evolve but not to extinct + "construction friendly solid-ish environment" (I imagine dolphins, squids and octopuses, and most monkeys plateaued because they lacked at least one ingredient of the magic combination, and this tends to be the rule...), but this should pretty much happen. And then you have the fact that our galaxy should have a few billions or tens of billions of Earth like planets based on what we know (probably more "life friendly" planets if you allow that other chemistries than "carbon + liquid water" could support life), it's pretty much unavoidable that there are quite a few human level species in the gallaxy. The scary bit it that there should be quite a few above that, that probably went past their first singularity/transcendence event and are no longer constrained by biology and individual mortality and probably dumped their biological bodies long ago... scary being the fact that we don't see any sign of their presence.

Symmetry 10y ago
The problem is that basic microbes only resperate over their surfaces so they have big square/cubed law limits on how large they can be and, by extension, on how complex their genomes can be. You need a hopeful monster that can run its metabolism throughout the cell to develop large genomes of the type that can support differentiated cells in multi-cellular creatures.
- 10y ago

cJ0th 10y ago

On a related note, there has been an interesting episode of BBC's CrowdScience. They reported that robots which go to Mars (to find out about microbial life) have to go through an extreme cleaning process to make sure that they contaminate Mars as little as possible with microbial life from our planet . http://www.bbc.co.uk/programmes/p04nmxzl http://www.bbc.co.uk/programmes/p04nmxzl