NASA: We'll find signs of alien life by 2025

[Jimster41]

Man, what a time to be alive... If they do.

I read this guy Chaisson (Harvard, Tufts) and his proposal is that complexification, is driven by the expansion of the universe and the laws of thermodynamics (toward nucleosynthesis and abiogenesis?) His writing left me with a sense that complex emergent replicating systems are probably ubiquitous. The physics is aimed at them. I believe we will find it in our solar system. I'd bet a sixer on it. In fact someday I think we'll look back and be embarrassed we thought we were remotely rare, or at least that the biochemistry of life was rare. We'll realize we are just mobile and chatty, for garden variety replicating slime.

The problem is distance. Distance is possibly the punchline to a very cruel joke.

 

[PWiz]

Man, what a time to be alive... If they do.

I read this guy Chaisson (Harvard, Tufts) and his proposal is that complexification, is driven by the expansion of the universe and the laws of thermodynamics (toward nucleosynthesis and abiogenesis?) His writing left me with a sense that complex emergent replicating systems are probably ubiquitous. The physics is aimed at them. I believe we will find it in our solar system. I'd bet a sixer on it. In fact someday I think we'll look back and be embarrassed we thought we were remotely rare, or at least that the biochemistry of life was rare. We'll realize we are just mobile and chatty, for garden variety replicating slime.

The problem is distance. Distance is possibly the punchline to a very cruel joke.

You do realize that if we find life not as complex as humans, it would spell danger for us, right?

 

[Jimster41]

Yeah, I think I buy that. It would probably be nice if we could spot them before they spot us...

 

[PWiz]

Erm, that's not exactly my point . Did you read the article in post #22?

 

[Monsterboy]

http://www.universetoday.com/113153/is-our-solar-system-weird/

Other stellar systems don’t seem to have the division of small rocky planets closer to the star and larger gas planets farther away. In fact, large Jupiter-type planets are generally found close to the star. This makes our solar system rather unusual.

Computer simulations of early planetary formation shows that large planets tend to move inward toward their star as they form, due to its interaction with the material of the protoplanetary disk. This would imply that large planets are often close to the star, which is what we observe. Large planets in our own system are unusually distant from the Sun because of a gravitational dance between Jupiter and Saturn that happened when our Solar System was young.

According to this article and a documentary i saw on discovery ,if we want to find life supporting planets in other star systems ,we need to find a weird solar system just like like our own where the gas giant (in our case Jupiter) is not too close to the sun indicating that it did not gobble up all the matter meant for inner rocky planets during the early days of the formation of solar system and allowed 2 or 3 rocky planets to exist between itself and it's star.

Without Saturn's intervention Jupiter might have gobbled up all the matter meant for inner planets i.e mercury,venus,earth and Mars would not exist ! This happens to be the case with most of the solar systems that we have spotted i.e a large gas giant orbiting close to it's star.

The movie "Avatar" offered an alternative theory of life evolving on a moon orbiting a gas giant.

 

[PWiz]

http://www.universetoday.com/113153/is-our-solar-system-weird/
According to this article and a documentary i saw on discovery ,if we want to find life supporting planets in other star systems ,we need to find a weird solar system just like like our own where the gas giant (in our case Jupiter) is not too close to the sun indicating that it did not gobble up all the matter meant for inner rocky planets during the early days of the formation of solar system and allowed 2 or 3 rocky planets to exist between itself and it's star.

Without Saturn's intervention Jupiter might have gobbled up all the matter meant for inner planets i.e mercury,venus,earth and Mars would not exist ! This happens to be the case with most of the solar system that we have spotted i.e a large gas giant orbiting close to it's star.

The movie "Avatar" offered an alternative theory of life evolving on a moon orbiting a gas giant right.

There's some evidence of life evolving in interstellar gas clouds under the presence of strong e.m. radiation. The asymmetric presence of amino acids on Earth (the left handed "bias") is also predicted to occur in these gas clouds when circularly polarized ultraviolet radiation is absorbed by different degrees by the chiral amino acids. Right handed amino acids have a higher peak absorbance for UV light, causing a greater proportion of them to be degraded by photolysis. However, for this enantioselectivity to occur, the band of polarized radiation must be small. Nevertheless, this mechanism provides some ground to assume that life doesn't necessarily need to begin on a rocky planet.

 

[Jimster41]

Just went back and read it. I've read just about everything by Alistair Reynolds. Some chilling (but also beautiful) stuff. In one (I can't remember which), humanoid life itself is considered a plague and a race of "Inhibitors" has set traps for it all over the place. We think they are pretty, and curious.

If everyone thinks it's better that we hide out, okay. But that seems existentially problematic also. For my part, I do like to think that the evolutionary principles of cooperation and symbiosis are also likely to propagate. Maybe that's Pollyanna, on the other hand fear is a defense mechanism, important surely, but also a potential barrier to thought and action.

 

[mfb]

You do realize that if we find life not as complex as humans, it would spell danger for us, right?

That is a very strong statement. It lowers our estimate of the probability that we will ever colonize the galaxy - especially if that life is quite complex (so it took more steps). It does not mean we would be doomed - there could be many inhabitated planetary systems if interstellar colonization turns out to be too difficult.

@Monsterboy: I don't see where they get that conclusion from, but the fact that they do not seem to account for observation bias indicates a poor quality of the article. Most gas giants we know are close to the star - simply because they are much easier to detect there. Finding a hot Jupiter is quite easy, finding a true Jupiter-analog is very hard (there are just a few stars where we would have found a planet like Jupiter). All those rocky Kepler planets could have gas giants further away.

 

[PWiz]

@mfb If complex life is discovered, it will be proof that the formation and evolution of life to complex levels is not uncommon (if we are able to find it in just another decade, then that means life was in close proximity to us, and considering the size of the observable universe, I would attribute this to a very high 'life' density). This would suggest that some very strong factor has prevented all such species formed in the past from evolving and reaching the level of development that would enable them to colonize the galaxy (we don't see them here right now), and since we're talking about a timescale were a million years amount to a sneeze, this is tantamount to saying that humans too must go through the same rigorous barrier, and there is no reason to assume we will succeed where most probably thousands have failed.

 

[mfb]

I know that argument, there is no need to repeat it. "Staying within the planetary system forever" is one sort of "fail to colonize the galaxy" - but certainly not the worst way to fail.

And this filter does not have to exist - we could be the first to start colonizing. The likelihood of that depends on several parameters that are poorly known.

 

[PWiz]

I know that argument, there is no need to repeat it. "Staying within the planetary system forever" is one sort of "fail to colonize the galaxy" - but certainly not the worst way to fail.

And this filter does not have to exist - we could be the first to start colonizing. The likelihood of that depends on several parameters that are poorly known.

Are you saying that was no habitable epoch? That in 13.8 billion years we are the only species to have come this far? A failure at galactic colonization of one specied can only delay the inevitable success of some other species. Five thousand years ago we were living in caves, and today we have GPS satellites out in space. I'm not entirely convinced by your argument.

 

[mfb]

Are you saying that was no habitable epoch?

No. But it certainly did not start a few million years after the big bang - long before the first stars formed, and even longer before the concentration of heavier elements from supernovae was sufficient to create planets like earth? A few billion years could be more realistic.

That in 13.8 billion years we are the only species to have come this far?

Let's say "within our galaxy". Well, can you rule it out?

Five thousand years ago we were living in caves, and today we have GPS satellites out in space.

And in five thousand years we could have extrasolar colonies. Finding other species capable of radio transmissions would indeed make this very unlikely, finding some photosynthesis happening somewhere does not.

 

[PWiz]

And in five thousand years we could have extrasolar colonies.

Exactly. Following your chain of reasoning/speculation that we could be one of the first intelligent species in the universe, I would say that it's very likely many other intelligent organisms formed in our galaxy around the same time. From such a large sample space, there would be so many who would have evolved to our current stage a few (hundred) thousand years before us (and that's not a lot on cosmological timescales). If 5 thousand years can make so much of a difference in development, then shouldn't there be a swarm of species beating us by leaps and bounds in technology? Even interstellar travel should be a piece of cake for them. This again doesn't answer why we don't see extraterrestrials all around us.

 

[mfb]

I would say that it's very likely many other intelligent organisms formed in our galaxy around the same time.

That looks like pure speculation to me.

Even interstellar travel should be a piece of cake for them.

And that as well.

 

[Monsterboy]

I don't see where they get that conclusion from, but the fact that they do not seem to account for observation bias indicates a poor quality of the article. Most gas giants we know are close to the star - simply because they are much easier to detect there. Finding a hot Jupiter is quite easy, finding a true Jupiter-analog is very hard (there are just a few stars where we would have found a planet like Jupiter). All those rocky Kepler planets could have gas giants further away.

So ,even if we come across a solar system exactly identical to ours which 10 or 20 light years away ,we will not able to detect either the Earth-analog or the Jupiter-analog ?

If gas giants as big as Jupiter can't be found because they are a little far away from their star ,then how did we find kepler planets or super Earth's ? these are quite small compared to the gas giants right? and they not very close to their star either.

 

[PWiz]

@mfb Us being the first and only intelligent organisms to develop in the galaxy does not seem very probable either. Where are you getting at?

On 4 November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sizedplanets orbiting in the habitable zonesof Sun-like stars and red dwarfs in the Milky Way,[4][5] 11 billion of which may be orbiting Sun-like stars.[6] The nearest such planet could be 12 light-years away, according to the scientists.[4][5]

Doesn't seem far from speculation. I mean only one planet with intelligent life in 40 billion?
And is it fair to rule out what can and cannot be achieved in thousands of years when we don't know what the next century might hold for us? In the early 1800s, scientists would laugh at you if you talked about sending a man-made object on Mars. I think the only thing about the future which we should be sure of is not to be sure about anything.

 

[rootone]

The fact remains though, that although Earth-like planets in a Sun-like solar system and within 100 ly seems a reasonable prospect,
and some such planets could provide a habitable environment, we have not yet discovered any sign of life, let alone intelligent life.
To me this implies that having the right conditions for life to survive, does not imply that life inevitably must arise.
There has to be some particularly rare circumstance which allows for a crucial step in abiogenesis to occur.
Hand-wavey guess here - that rare circumstance is whatever it takes to produce a simple self replicating molecule, and sufficient resources in the environment for the replication to actually occur.

 

[Astudious]

@mfb If complex life is discovered, it will be proof that the formation and evolution of life to complex levels is not uncommon (if we are able to find it in just another decade, then that means life was in close proximity to us, and considering the size of the observable universe, I would attribute this to a very high 'life' density). This would suggest that some very strong factor has prevented all such species formed in the past from evolving and reaching the level of development that would enable them to colonize the galaxy (we don't see them here right now), and since we're talking about a timescale were a million years amount to a sneeze, this is tantamount to saying that humans too must go through the same rigorous barrier, and there is no reason to assume we will succeed where most probably thousands have failed.

Clever argument but the flaw, as I see it, is that humanity has almost certainly passed this barrier way behind.

If the fruition of life is common (or at least reasonably probable) then we can suppose it likely that the emergence of complex and (ultimately) intelligent and advanced life is itself highly uncommon, simply by observing the number of species which fail to make it to any kind of high degree of complexity. Then the extraordinary event that has occurred to place us in front of our computers today is not abiogenesis on Earth (which we have suggested here, is not that extraordinary) but rather that we developed from the simplistic biochemical machines that barely constitute "life" into the evolved emergent, highly-complex products we are. The barriers to this occurring are (in my opinion almost certainly) in the first steps of complex growth; once complex physiology/biology gets well underway, evolution takes over and from there a highly-intelligent species seems almost certain to arise.

Therefore, finding life less complex than humans is just a sign that the really-rare event on Earth is the formation of highly-complex life here.

If we were to find traces of several civilizations as complex as ours that failed to make it further, that would corroborate your point. But think about how unlikely that is!

I myself am, by the way, not of the opinion that complex growth of life is truly the extraordinary step but rather than abiogenesis is itself (but this is fairly unsubstantiated by scientific standards of evidence, just speculation).

 

[Astudious]

I know that argument, there is no need to repeat it. "Staying within the planetary system forever" is one sort of "fail to colonize the galaxy" - but certainly not the worst way to fail.

Interesting. Population growth could cause serious problems at that point, and it doesn't seem as far off into the future necessarily as being able to travel to and easily colonize other solar systems. May this will be the end of the human race?!

Somehow, I find it unconvincing that other lifeforms were stopped at the same place. :P

 

[PWiz]

@rootone I think drawing any conclusions at this stage would be premature considering the fact that we haven't even fully explored the Martian surface yet, let alone any other planet in the solar system. My entire argument is based on "if NASA finds life by 2025."
@Astudious Evolution is like a wheel on top of a very tall hill. It's difficult to get the wheel rolling, but once it does, it will definitely lead to more complex organisms over time (even though it's random). One of the "hiccups" to the evolution of intelligent species like us (other than the formation of primordial life itself) is the transition from unicellular prokaryotes to multicellular eukaryotes (if I remember correctly, it nearly took a billion years for this transition to occur, and life on Earth itself is just about 3.5 billion years old; the longer the transition period, the greater the probability that the transition was unlikely and rare). I guess I should clarify: by discovering complex organisms, I mean discovering a "composite" organism - a collective group of structures (cells) in which the chemistry of life occurs, functionally related to each other, but fundamentally distinct (or something along those lines; you get the idea). Now that would be proof that formation of life to that level of complexity is not rare, and we have extremely few likely candidates left for "The Great Filter" which would stop the wheel from rolling towards levels of intelligence comparable to humans, since we don't have any other period of evolutionary stagnation worth mentioning on this timescale. It would be a sign that the filter is ahead of us intead, and that wouldn't be a very pretty scenario.

 

[rollingstein]

How is that a conflict of interest? Everyone has the right to flog their own livelihood.

Yes. But I'd be very wary of believing that estimate.

 

[Astudious]

@Astudious Evolution is like a wheel on top of a very tall hill. It's difficult to get the wheel rolling, but once it does, it will definitely lead to more complex organisms over time (even though it's random). One of the "hiccups" to the evolution of intelligent species like us (other than the formation of primordial life itself) is the transition from unicellular prokaryotes to multicellular eukaryotes (if I remember correctly, it nearly took a billion years for this transition to occur, and life on Earth itself is just about 3.5 billion years old; the longer the transition period, the greater the probability that the transition was unlikely and rare). I guess I should clarify: by discovering complex organisms, I mean discovering a "composite" organism - a collective group of structures (cells) in which the chemistry of life occurs, functionally related to each other, but fundamentally distinct (or something along those lines; you get the idea). Now that would be proof that formation of life to that level of complexity is not rare, and we have extremely few likely candidates left for "The Great Filter" which would stop the wheel from rolling towards levels of intelligence comparable to humans, since we don't have any other period of evolutionary stagnation worth mentioning on this timescale. It would be a sign that the filter is ahead of us intead, and that wouldn't be a very pretty scenario.

I agree: this falls under, I suppose, the category "if we find traces of several civilizations as complex as ours" in my post, which must be extended to "if we find traces of several biological entities that would be foreseen by the standard procedure of evolution as we know it to proceed to the same degree of advancement or complexity as our civilization within a timescale of a few billion years at most".

Which, personally, I do not think probable.

 

[Chronos]

There are as many possible explanations for the Fermi paradox as odds against any particular one being true. It is ridiculously improbable that abiogenesis is a process unique to earth. Yes, we haven't duplicated it in the lab, but, that's not the first example of a natural process we struggle to reproduce. Life, and intelligent life, are two different questions. In a utopian environment, there is scarcely any point in intelligence. You need sustained selection pressure to elicit a learn or burn response from DNA, IMO. The nature and timing of events sufficient to prod intelligence without destroying it could be the 'great filter'. We humans spent most of our history closer to extinction than success, before we began to collectivize knowledge and create civilizations. Intelligent life like our own might truly be a statistical oddity that has only occurred a few handfuls of times over the history of this galaxy. However disappointing, it is not unreasonable to suspect we could currently be the most advanced inhabitants of our galaxy.

 

[mfb]

So ,even if we come across a solar system exactly identical to ours which 10 or 20 light years away ,we will not able to detect either the Earth-analog or the Jupiter-analog ?

Depends on how hard we look and how lucky we are with the orientation of the orbits, but it would be very challenging unless we are very lucky.

If gas giants as big as Jupiter can't be found because they are a little far away from their star ,then how did we find kepler planets or super Earth's ? these are quite small compared to the gas giants right? and they not very close to their star either.

Kepler needs at least three transits to find a planet. At about 4 years observation time in the primary mission, Kepler could not find planets with an orbital period of more than two years at all, and if you add the time of the first transit and various downtimes every observation with a period above one year is very lucky. Also, the planets have to transit the host star - this is becoming less likely for planets with a larger separation from the star. All that is independent of the size of the planet.
To find earth-sized planets you have to measure the luminosity very precisely, better than 1 part in 10000. That was not possible for all stars, but there are many stars where it was possible.

Us being the first and only intelligent organisms to develop in the galaxy does not seem very probable either.

Pure speculation from your side again. We don't know. If there is no great filter, it is likely. For your claim you would have to show the existence of such a filter, which would be a great publication on its own.

I mean only one planet with intelligent life in 40 billion?

Not one, just the first one. Also, where is your point?

And is it fair to rule out what can and cannot be achieved in thousands of years

To follow your argument, you have to do exactly that.

If we were to find traces of several civilizations as complex as ours that failed to make it further, that would corroborate your point.

That for sure.

Evolution is like a wheel on top of a very tall hill. It's difficult to get the wheel rolling, but once it does, it will definitely lead to more complex organisms over time (even though it's random).

If you can prove that, write a paper about it. If you cannot, please don't write speculations as facts.

 

[lpetrich]

I could not find out what Dr. Stofan expects to be detected in that time. I also think that that is very overoptimistic. Let's see what an organism needs to metabolize and grow:

1. Liquid water, to serve as a solvent and raw material: H2O
2. Several other elements: C, N, P, S, various metal ions (can be trace amounts)
3. Usable thermodynamic disequilibrium, like chemical disequilibrium or suitably-energetic photons

These are all extrapolated from the Earth's biota, but there are plausible arguments for the first two, and the third one is a necessity. It enables organisms to appear to violate the Second Law of Thermodynamics by metabolizing and growing and reproducing and moving and the like.

Organisms can alter their environments in various observable ways, sometimes massively, like photosynthesizers releasing large quantities of molecular oxygen into the atmosphere. This is in chemical disequilibrium with its producers and with the less-oxidized crustal rocks. Rocks with Fe++ instead of Fe+++. But there can be nonbiological processes that produce chemical disequilibria. Like serpentinization: FeO + (1/2)*H2O -> (1/2)*Fe2O3 + (1/2)*H2. FeO has Fe++ and Fe2O3 has Fe+++. The resulting hydrogen will be out of equilibrium with a neutral or oxidizing atmosphere. Neutral: lots of CO2 and/or N2. Oxidizing: lots of O2.

Mars

Its surface is borderline at best for liquid water, being cold with a thin atmosphere, though there is an abundance of evidence that it had oceans and rivers some 4 billion years ago.

However, a few km down may be more friendly to organisms, and there is possible evidence of their presence: methane. Tiny amounts of it have been detected in Mars's atmosphere. (Mars methane detection and variability at Gale crater: Science magazine) It's typically a part per billion by volume, though it is sometimes greater.

It could be produced by 4H2 + CO2 -> 2H2O + CH4, where the H2 comes from serpentinization. It could be some nonbiological reaction alongside the serpentinization, or it could be organisms like Earth's methanogens. These organisms get their energy from the aforementioned reaction, and are a major source of methane in the Earth's atmosphere.

It might be possible to go further by finding the isotopic composition of Martian methane and comparing it to that of Martian water and Martian CO2. As a check, this ought to be done on Earth methanogens to see if they produce any distinctive signatures of isotopes.

Interior oceans of large icy moons

Moons like Europa, Ganymede, Callisto, Enceladus, and maybe also Titan, Triton, and Ceres (not a moon, but it has a similar size). They have the first two ingredients, but there is a serious question of whether any of them have the third ingredient: some usable disequlibrium like chemical disequilibrium.

There is a possibility for that. Several of them have rocky interiors, and they may get heated enough from radioactivity or tides to cause serpentinization and its production of hydrogen. This would likely be in disequilibrium with some of the contents the interior ocean.

Titan's surface

That would require some rather exotic biochemistry, starting with having hydrocarbons as a solvent. It would be biochemistry with H, C, N, but not much O or others. It doesn't look like it could make the necessary amount of complexity.

Extrasolar planets

The best chance here is doing spectroscopy and looking for out-of-equilibrium atmosphere gases like O2. That's going to be VERY difficult. For starters, one would have to do it in the infrared to get away from the bulk of the planet's star's light.

 

[PWiz]

Pure speculation from your side again. We don't know.

You don't need to know the actual result to ascribe a probability to it (no one tosses a fair coin 1000 times to assign a probability, now do they?) . What is unlikely is unlikely, nothing more to it. I'm not claiming anything, just commenting on how probable it is. After looking at the numbers I posted in #46, one would require some serious convincing (looking at the size and age of the universe) to think we are the first one. A lot of evidence is required to believe what is not obvious at all.

Not one, just the first one. Also, where is your point?

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us. Also, the probability of being the first one is not very different from being the only one. I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

To follow your argument, you have to do exactly that.

I have - please read the last sentence of post #46.

If you can prove that, write a paper about it. If you cannot, please don't write speculations as facts.

I would like to see some figures here. Has any period of evolutionary stagnation exceeded the nuclear transition of cells? How many early eukaryotes do we see around us? How do their numbers compare to prokaryotes? The vast number of bacteria and archaea still present is staggering - the evolution step still hasn't managed to convert most prokaryotes. I thought that this was a well established fact.

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable. And I was unaware that assigning probabilities to events in large sample spaces after looking at some well known facts counted as speculation. However, I'll drop the argument here if you insist.

 

[mfb]

(no one tosses a fair coin 1000 times to assign a probability, now do they?)

We are not tossing a fair coin, we are tossing an object where we don't even know how many sides it has. Saying one side is unlikely is pure speculation.

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us.

Yes, if such a filter exists. And even then it is just a relative statement, not an absolute one.

Also, the probability of being the first one is not very different from being the only one.

It is a massive difference. There could be millions of planets with life where intelligent life like ours might evolve within the next billions of years.

I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

Which is pure speculation, yes.

I would like to see some figures here.

Why do I have to provide evidence for a claim you made?

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable.

I did not claim that.
I said "if there is no great filter and the probability that life eventually colonizes the galaxy is high, then it is likely that we are the first - based on the observation that we do not see evidence of alien life doing that before us.
Note that I did not assign any probability to this "if" condition.

I don't think this discussion is moving forwards, my last post on those probabilities.

 

[PWiz]

@mfb Alright, so in short, all of this is mostly dependent on the existence of a filter (for which we have no evidence yet, yes) in the first place, right?

 

[mfb]

That will certainly be relevant for probability estimates, sure.

 

[Astudious]

You don't need to know the actual result to ascribe a probability to it (no one tosses a fair coin 1000 times to assign a probability, now do they?) . What is unlikely is unlikely, nothing more to it. I'm not claiming anything, just commenting on how probable it is. After looking at the numbers I posted in #46, one would require some serious convincing (looking at the size and age of the universe) to think we are the first one. A lot of evidence is required to believe what is not obvious at all.

I had a look at Post 46. Doesn't convince (read on).

This: the more complex the organisms discovered, the greater the probability that the great filter is ahead of us. Also, the probability of being the first one is not very different from being the only one. I've already stated in my previous posts how low the probability of there being no Great Filter at all is.

Sure. If by "Great Filter" you mean to include potentially, abiogenesis itself.

I have - please read the last sentence of post #46.

I'd really appreciate if you can give some statistics to support your argument that "Earth being 1 in 40 billion planets in the galaxy to support (complex) life first in a universe 13.8 billion years old" is probable. And I was unaware that assigning probabilities to events in large sample spaces after looking at some well known facts counted as speculation. However, I'll drop the argument here if you insist.

Unfortunately giving some number of "Earth-sizedplanets orbiting in the habitable zonesof Sun-like stars and red dwarfs in the Milky Way ...orbiting Sun-like stars" is deeply insufficient. Hell, every planet in the universe could meet these criteria without it necessarily proving your point.

The Goldilocks Zone is not considered a serious barrier in the question of whether there is extraterrestrial life, because, of course, there are billions (at least) of planets which would match this criterion. The real barrier must be in the biochemistry of abiogenesis. Whether or not that is a process of any reasonable repeatability is unknown. Perhaps it was a freak occurrence on the order of (pulling a number from nowhere) 1 in 10²⁰⁰ Goldilocks planets. We cannot know or say that this is improbable ^until we a) see life elsewhere having emerged independently or b) understand abiogenesis and its initiation pathways better. This is something humans have crucially not been able to kickstart in the lab. We don't know how it happens and it looks like a fairly rare event from all lab trials; the point is, it could be almost infinitesimally improbable (and thus the chance of it happening elsewhere in our same universe is practically 0, regardless of how many Goldilocks planets there are), because we are just here to talk about it as its product.

We can only suppose that, if it is more probable than this, there are not too many other filters before our stage of evolution. I am inclined to suggest that the only reasonable "Great Filter", besides the first generation of life, would be amalgamation into working complex life that we discussed before. I'd be surprised to learn the "Great Filter" is actually something that hits civilizations once already well-evolved.