6 ms·

Even though we have only one datapoint, I wonder how much can be inferred from this planet's life characteristics. First, life came about rather shortly after

Even though we have only one datapoint, I wonder how much can be inferred from this planet's life characteristics. First, life came about rather shortly after the planet was able to sustain it. So this timing is either very unlikely, or biogenesis has a high probability of happening, or the initial life got seeded from off planet (from a very rare initial phenomenon). Second, all the biosignatures from all forms of life are similar. For example, corality (left handed versus right handed molecules) is the same in all life examples we had. So that means that biogenesis happened only once. Otherwise we would have multiple unrelated examples (yes, there is the possibility that one form "ate everything else", but we have all kinds of variety instead of only one organism becoming dominate). So if biogenesis happened only once (for all of our bio examples), then it is either a rare event that just happened to occur very shortly after the planet cooled, or it happened sometime before Earth was hospitable for life and elsewhere in the universe. Does any of this make sense? Or am I reading too much into the tea leaves?

inflatableDodo 7y ago
>Even though we have only one datapoint I think we can wrangle a few more datapoints if we are creative with perspective, for example, we have extremely good evidence to suggest that the planet Mars is currently inhabited by alien robots.
infectoid 7y ago
Your tea leaves are sound. I think this is why those of us interested in this are very much hanging out for results from our explorations of Mars. It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. What are the chances? On the positive side Mars had pretty much all the ingredients for life (chemically) and had a long enough period for at least something intersting to develop. On the negative side, the environment was still different to ours (gravity, climate, whether, etc). We still aren't clear on what conditions need to met for like to get going. This is why both positive or negative results on Mars are exciting. My favourite theory is that life actually takes ages to get started so much so that it started on Mars and finished on Earth (from Mars being impacted and debris making it to Earth). Kind of like a passing of the torch. Mars: "Crap. I'm dying. Hey Earth, can you take this thing I've been working on?" Earth: "Yep. No worries. I got this. Will try to send some back in a few billions years. Take care."
- opportune 7y ago
  >It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. Well there's also Titan, Enceladus, and Europa right? Titan is by far the most exotic but it could serve as an example of what happens when life evolves under a radically different environment. It has some complex organic molecules there and a very interesting/varied geology and topology. Enceladus and Europa could exhibit very similar conditions to those of the deep sea on Earth as well, which could very well be where life originated. Also at one point even Earth could have became a "snowball" planet and still able to sustain life: https://en.wikipedia.org/wiki/Snowball_Earth https://en.wikipedia.org/wiki/Snowball_Earth
- codesushi42 7y ago
  >It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. You mean carbon based life. Methane based life may be a possibility, and you wouldn't have found it on Mars. You might find it on Titan.
  - dredmorbius 7y ago
    Methane is an organic (carbon-chain) molecule: CH4. Titan would have a low-temperature carbon-based chemistry, but it would remain carbon-based if focused on methane. Alternative hypothetical biochemistries usually focus on silicon.
    - codesushi42 7y ago
      True. But a methane based lifeform would be radically different than the carbon based lifeforms found on Earth, and would have emerged separately.
      - dredmorbius 7y ago
        Oddly, that wasn't your claim.
dragonwriter 7y ago
> So that means that biogenesis happened only once. No, it just means that only one lineage did well enough in competition that we can find examples to study its biomarkers. Or that there are factors we don't yet understand that favor similar biomarkers in independent lineages. Or...luck. > if biogenesis happened only once (for all of our bio examples), then it is either a rare event that just happened to occur very shortly after the planet cooled, or it happened sometime before Earth was hospitable for life and elsewhere in the universe. Or biogenesis itself changed the environment in a way which made it no longer conducive to biogenesis.
data_required 7y ago
A very minor note on your fun comment- the word is spelled "chirality" not "corality" :).
throwaway2048 7y ago
The new life may have spread very rapidly and ended the conditions that abiogenesis required, in a sense it had a massive "leg up" on the "evolution" of non-living compounds, and we already know that species that get out competed are quickly driven to extinction. Consider for example that abiogenesis is probably impossible in an atmosphere containing oxygen, because everything gets oxidized too fast, although free oxygen in the air happened quite a long time after life arose. To abiogenicly form long chain carbons you need a free oxygenless reducing environment, oxygen from the new microbes could have easily poisoned all the viable sites for abiogenesis.
natch 7y ago
I like the thoughts you're exploring here. But I would be cautious calling a billion years or so "shortly" even in the context of a four-something billion year old planet. A billion is a very big number, especially when you multiply it by how many trillions of little potential multi-dimensional petri dish situations were around for each second of each year of those billion years. And it could have happened only once because once established, it tends, on a timescale orders of magnitude shorter than a billion years, to squelch the appearance of other forms, at a minimum by guiding them along with its template, or alternatively by smothering them. But this all says nothing about whether it happened on Earth or elsewhere. Either one could still be true.
- derekp7 7y ago
  I thought it was more like 400 million years between water and the first life -- and that is the oldest life we have evidence of. It could conceivably take a couple hundred million years for life to go from the initial spark, to having evolved enough (and have a sufficient population) to leave detectable fossils.
marcosdumay 7y ago
> So this timing is either very unlikely, or biogenesis has a high probability of happening, or the initial life got seeded from off planet Or life can only appear on young planets (maybe while it's hot), or some astronomical event triggered it (Moon?), or there are enough hard steps on the path to intelligence that it couldn't appear if life took too long to form. It's a good question anyway. > So that means that biogenesis happened only once. Life has repeatedly shown a tendency of consuming all available raw matter and populating every niche. Biogenesis happening only once is completely non-surprising.
- mar77i 7y ago
  There is a rather intriguing BBC documentary "Do we really need the moon?" about the topic on YouTube. The argument being made was that the moon propelled the chemical clockworks to develop life in a time when the moon was much closer, hence its tidal forces much stronger. To me that would mean that, Mars has, for a lack of such history, a weaker case for being dubbed the origin of life, unless research came across really strong evidence. Like, it would have to be from a time before Earth cooled down enough to even remotely harbor life.
rjurney 7y ago
How long did it take for life to exist after there were oceans?

inflatableDodo 7y ago

>Even though we have only one datapoint I think we can wrangle a few more datapoints if we are creative with perspective, for example, we have extremely good evidence to suggest that the planet Mars is currently inhabited by alien robots.

infectoid 7y ago

Your tea leaves are sound. I think this is why those of us interested in this are very much hanging out for results from our explorations of Mars. It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. What are the chances? On the positive side Mars had pretty much all the ingredients for life (chemically) and had a long enough period for at least something intersting to develop. On the negative side, the environment was still different to ours (gravity, climate, whether, etc). We still aren't clear on what conditions need to met for like to get going. This is why both positive or negative results on Mars are exciting. My favourite theory is that life actually takes ages to get started so much so that it started on Mars and finished on Earth (from Mars being impacted and debris making it to Earth). Kind of like a passing of the torch. Mars: "Crap. I'm dying. Hey Earth, can you take this thing I've been working on?" Earth: "Yep. No worries. I got this. Will try to send some back in a few billions years. Take care."

opportune 7y ago
>It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. Well there's also Titan, Enceladus, and Europa right? Titan is by far the most exotic but it could serve as an example of what happens when life evolves under a radically different environment. It has some complex organic molecules there and a very interesting/varied geology and topology. Enceladus and Europa could exhibit very similar conditions to those of the deep sea on Earth as well, which could very well be where life originated. Also at one point even Earth could have became a "snowball" planet and still able to sustain life: https://en.wikipedia.org/wiki/Snowball_Earth https://en.wikipedia.org/wiki/Snowball_Earth
codesushi42 7y ago
>It's pretty much our only opportunity to see if life emerged twice in the same planetary system under similar conditions. You mean carbon based life. Methane based life may be a possibility, and you wouldn't have found it on Mars. You might find it on Titan.
- dredmorbius 7y ago
  Methane is an organic (carbon-chain) molecule: CH4. Titan would have a low-temperature carbon-based chemistry, but it would remain carbon-based if focused on methane. Alternative hypothetical biochemistries usually focus on silicon.
  - codesushi42 7y ago
    True. But a methane based lifeform would be radically different than the carbon based lifeforms found on Earth, and would have emerged separately.
    - dredmorbius 7y ago
      Oddly, that wasn't your claim.

dragonwriter 7y ago

> So that means that biogenesis happened only once. No, it just means that only one lineage did well enough in competition that we can find examples to study its biomarkers. Or that there are factors we don't yet understand that favor similar biomarkers in independent lineages. Or...luck. > if biogenesis happened only once (for all of our bio examples), then it is either a rare event that just happened to occur very shortly after the planet cooled, or it happened sometime before Earth was hospitable for life and elsewhere in the universe. Or biogenesis itself changed the environment in a way which made it no longer conducive to biogenesis.

data_required 7y ago

A very minor note on your fun comment- the word is spelled "chirality" not "corality" :).

throwaway2048 7y ago

The new life may have spread very rapidly and ended the conditions that abiogenesis required, in a sense it had a massive "leg up" on the "evolution" of non-living compounds, and we already know that species that get out competed are quickly driven to extinction. Consider for example that abiogenesis is probably impossible in an atmosphere containing oxygen, because everything gets oxidized too fast, although free oxygen in the air happened quite a long time after life arose. To abiogenicly form long chain carbons you need a free oxygenless reducing environment, oxygen from the new microbes could have easily poisoned all the viable sites for abiogenesis.

natch 7y ago

I like the thoughts you're exploring here. But I would be cautious calling a billion years or so "shortly" even in the context of a four-something billion year old planet. A billion is a very big number, especially when you multiply it by how many trillions of little potential multi-dimensional petri dish situations were around for each second of each year of those billion years. And it could have happened only once because once established, it tends, on a timescale orders of magnitude shorter than a billion years, to squelch the appearance of other forms, at a minimum by guiding them along with its template, or alternatively by smothering them. But this all says nothing about whether it happened on Earth or elsewhere. Either one could still be true.

derekp7 7y ago
I thought it was more like 400 million years between water and the first life -- and that is the oldest life we have evidence of. It could conceivably take a couple hundred million years for life to go from the initial spark, to having evolved enough (and have a sufficient population) to leave detectable fossils.

marcosdumay 7y ago

> So this timing is either very unlikely, or biogenesis has a high probability of happening, or the initial life got seeded from off planet Or life can only appear on young planets (maybe while it's hot), or some astronomical event triggered it (Moon?), or there are enough hard steps on the path to intelligence that it couldn't appear if life took too long to form. It's a good question anyway. > So that means that biogenesis happened only once. Life has repeatedly shown a tendency of consuming all available raw matter and populating every niche. Biogenesis happening only once is completely non-surprising.

mar77i 7y ago
There is a rather intriguing BBC documentary "Do we really need the moon?" about the topic on YouTube. The argument being made was that the moon propelled the chemical clockworks to develop life in a time when the moon was much closer, hence its tidal forces much stronger. To me that would mean that, Mars has, for a lack of such history, a weaker case for being dubbed the origin of life, unless research came across really strong evidence. Like, it would have to be from a time before Earth cooled down enough to even remotely harbor life.

rjurney 7y ago

How long did it take for life to exist after there were oceans?