PDA

View Full Version : Superhabitable Worlds



A.DIM
2014-Feb-06, 03:17 PM
Superhabitable Worlds (http://online.liebertpub.com/doi/pdf/10.1089/ast.2013.1088)

Abstract:
To be habitable, a world (planet or moon) does not need to be located in the stellar habitable zone (HZ), and worlds in the HZ are not necessarily habitable. Here, we illustrate how tidal heating can render terrestrial or icy worlds habitable beyond the stellar HZ. Scientists have developed a language that neglects the possible existence of worlds that offer more benign environments to life than Earth does. We call these objects ‘‘superhabitable’’ and discuss in which contexts this term could be used, that is to say, which worlds tend to be more
habitable than Earth. In an appendix, we show why the principle of mediocracy cannot be used to logically explain why Earth should be a particularly habitable planet or why other inhabited worlds should be Earth-like. Superhabitable worlds must be considered for future follow-up observations of signs of extraterrestrial life. Considering a range of physical effects, we conclude that they will tend to be slightly older and more massive than Earth and that their host stars will likely be K dwarfs. This makes Alpha Centauri B, which is a member of
the closest stellar system to the Sun and is supposed to host an Earth-mass planet, an ideal target for searches for a superhabitable world.

Notions of "habitability" or "goldilocks zones" are ever-changing but they may be guiding us in the wrong directions in our searches for life elsewhere.

I'm of the opinion that just as earth-life has evolved and adapted to countless niches on this planet, so too would cosmic-life evolve and adapt to countless niches in this universe.

Selfsim
2014-Feb-06, 09:05 PM
… Notions of "habitability" or "goldilocks zones" are ever-changing but they may be guiding us in the wrong directions in our searches for life elsewhere.The most striking point of note from this article is that its slowly becoming clear for some that no-one, anywhere, has the slightest idea of what they're looking for, or where to look for it!

The search for exo-life has become some kind of obsession, and has no place in a scientifically based, systematic exploration strategy of our planetary surroundings.


I'm of the opinion that just as earth-life has evolved and adapted to countless niches on this planet, so too would cosmic-life evolve and adapt to countless niches in this universe.… Opinion based science … in its purest form!

Noclevername
2014-Feb-06, 11:20 PM
mediocracy

Do they mean mediocrity?

A.DIM
2014-Feb-07, 01:36 AM
The most striking point of note from this article is that its slowly becoming clear for some that no-one, anywhere, has the slightest idea of what they're looking for, or where to look for it!

The search for exo-life has become some kind of obsession, and has no place in a scientifically based, systematic exploration strategy of our planetary surroundings.

Rubbish.
"Science" was born out of a desire to understand our place in the universe; "Are we alone?" is paramount.
Ironically, however "obsessed" you perceive those looking for exo life are, the was I see it they haven't been looking since the Viking landers.


… Opinion based science … in its purest form!

Rather, science based opinion.

I'm sorry, do you fancy yourself doing science here?

A.DIM
2014-Feb-07, 01:48 AM
Do they mean mediocrity?

That could be deduced from the rest of that sentence, no?
That's what I assumed.

Selfsim
2014-Feb-07, 02:08 AM
… "Science" was born out of a desire to understand our place in the universe; "Are we alone?" is paramount.Why is this question 'paramount' for science?
Science can proceed just fine with precisely no answers to this ideologically based question(??)


Ironically, however "obsessed" you perceive those looking for exo life are, the was I see it they haven't been looking since the Viking landers.Whilst this comment seems lost in editing errors, I'll interpret your point as being that because there have been no specific life detection missions since Viking, there appears to be no 'empowered people', actually undertaking such a quest … Which is a good thing … It seems the futility of the Viking mission lessons have been learned by those who actually accept the responsibility which goes with their empowerment to explore.

They also appear to treat claims of 'Martian Mushrooms', (made by those who accept no responsibilities for their actions), with an appropriate degree of light-heartedness, too. :)

KlausH
2014-Feb-07, 03:23 AM
Rubbish.
"Science" was born out of a desire to understand our place in the universe; "Are we alone?" is paramount.

Why is this question 'paramount' for science?
Science can proceed just fine with precisely no answers to this ideologically based question(??)

I definitely agree with A.DIM that the question whether or not we are alone is paramount to science.
It is certainly one of the most interesting ones.

If you are happy just analyzing the movement of billiard balls on a pool table, be my guest.

Everybody here knows: you clearly have huge problems with the topic of the LiS forum.

Why do you keep posting the same stuff here over and over again?

It seems to me you are the one with an ideological bias.
The question whether or not we are alone most certainly does not qualify as "ideologically biased".

Selfsim
2014-Feb-07, 06:28 AM
... The question whether or not we are alone most certainly does not qualify as "ideologically biased".I didn't actually use the term 'bias', I used 'based'.

However, as I look at the question of: "Are we alone?" more closely, it is by necessity biased .. 'We' is clearly self-reflective .. which is about as biased as it gets, I suppose(?)

In as far as this ideology permeates into the study in the OP; the concept of a 'Habitable Zone', (as it applies beyond Earth's immediate locale), is clearly viewed by the authors as being sufficiently unconstrained, (due to the dearth of .. no .. non-existent empirical data from beyond Earth-life), as to be able to be rewritten by merely altering the commonly held perception that the coupling between Earth's life amenable Astrophysical location and the observation of long established Earth-life are in fact, the only criteria for 'likely' finding life elsewhere. The very fact that they are attempting to question (and readdress) this perception, demonstrates a recognition by the authors that the commonly held belief, (that these two observations, when coupled together, will lead to a 'more likely' exo-life discovery), is alterable ... even in the absence of any pertinent empirical data from beyond Earth (which could lead to any conclusion that this might actually be so). If the perception they are addressing, (albeit a logically principled one), is also not the very definition of an ideology, then I don't know what is ...

Selfsim
2014-Feb-07, 07:29 AM
Take a look at this ...
Eventually, just as the Solar System turned out to be everything but typical for planetary systems, Earth could turn out everything but typical for a habitable or, ultimately, an inhabited world. Our argumentation can be understood as a refutation of the Rare Earth hypothesis. Ward and Brownlee (2000) claimed that the emergence of life required an extremely unlikely interplay of conditions on Earth, and they concluded that complex life would be a very unlikely phenomenon in the Universe. While we agree that the occurrence of another truly Earth-like planet is trivially impossible, we hold that this argument does not constrain the emergence of other inhabited planets. We argue here in the opposite direction and claim that Earth could turn out to be a marginally habitable world. In our view, a variety of processes exists that can make environmental conditions on a planet or moon more benign to life than is the case on Earth.They seem to think 'an argument' and even a subsequent 'agreement', occurring in a debate here on Earth, might actually have some bearing on what may or may not have emerged on other planets! Completely hilarious!

Also, their reasoning seems to allow them to 'trivially' dismiss the possibility of another 'truly Earth-like planet', (whatever that is), ... outright! ... whilst simultaneously allowing them to favor the possibility of Earth being only 'a marginally habitable planet'!

Their 'arguments' are just as ideologically based (biased?) as those they are attempting to counter!

Not much wonder there hasn't been any serious life detection missions since Viking, if this is the quality of reasoning being presented to guide such a (hypothetical) search!

Van Rijn
2014-Feb-07, 09:06 AM
In as far as this ideology permeates into the study in the OP; the concept of a 'Habitable Zone', (as it applies beyond Earth's immediate locale), is clearly viewed by the authors as being sufficiently unconstrained, (due to the dearth of .. no .. non-existent empirical data from beyond Earth-life), as to be able to be rewritten by merely altering the commonly held perception that the coupling between Earth's life amenable Astrophysical location and the observation of long established Earth-life are in fact, the only criteria for 'likely' finding life elsewhere.


So you didn't read the article? Actually, they go into a fair amount of technical detail when defining "habitability" as they are using the term. They do not appear to claim that the entire "set" of life must be constrained to the requirements of Earth life, but of course the requirements for Earth life are known, so is a reasonable place to start. They then are considering those requirements and applying what has been learned about other star systems. This is to help establish what may be the better systems to look at as telescopes and instruments improve.

For example, they note that Alpha Centauri B will have a longer time on the main sequence than our sun, and its luminosity will not change as quickly as the Sun's, yet still not a particularly dim star. Planets around stars like Alpha Centauri B could have habitable conditions longer than Earth ("super-habitable") and may be better candidates for future study than hotter stars like our sun.

There is no absolute claim of what must be. Rather it is just a part of the scientific process I would expect given our expanding knowledge and increasing observational capability. Dismissing this process is like dismissing all the work and consideration that led to finding and evaluating exoplanets.

Van Rijn
2014-Feb-07, 09:25 AM
Take a look at this ...They seem to think 'an argument' and even a subsequent 'agreement', occurring in a debate here on Earth, might actually have some bearing on what may or may not have emerged on other planets! Completely hilarious!


Right! And it's laughable that anyone ever thought the existence of planets in our solar system could have any bearing on the existence of planets elsewhere! Pure ideology! Unscientific thinking!


Also, their reasoning seems to allow them to 'trivially' dismiss the possibility of another 'truly Earth-like planet', (whatever that is), ... outright! ... whilst simultaneously allowing them to favor the possibility of Earth being only 'a marginally habitable planet'!


Which leads me to think you didn't actually read the article. They were pointing out that true Earth-twins are unlikely, but that other worlds could have more widespread habitable areas, or be habitable for a longer period than the Earth likely will be.


Not much wonder there hasn't been any serious life detection missions since Viking, if this is the quality of reasoning being presented to guide such a (hypothetical) search!

I have no idea why you'd think those are even connected issues.

Selfsim
2014-Feb-07, 10:40 AM
So you didn't read the article? Actually, they go into a fair amount of technical detail when defining "habitability" as they are using the term. They do not appear to claim to claim that the entire "set" of life must be constrained to the requirements of Earth life, but of course the requirements for Earth life are known, so is a reasonable place to start. They then are considering those requirements and applying what has been learned about other star systems. This is to help establish what may be the better systems to look at as telescopes and instruments improve.

For example, they note that Alpha Centauri B will have a longer time on the main sequence than our sun, and its luminosity will not change as quickly as the Sun's, yet still not a particularly dim star. Planets around stars like Alpha Centauri B could have habitable conditions longer than Earth ("super-habitable") and may be better candidates for future study than hotter stars like our sun.

There is no absolute claim of what must be. Rather it is just a part of the scientific process I would expect given our expanding knowledge and increasing observational capability. You need to re-read what I said.

They are attempting to counter the idea that Earth's specific Astrophysical environment is what the search should focus on.
Which is what I said.
(And what you just said, again).


Dismissing this process is like dismissing all the work and consideration that led to finding and evaluating exoplanets.The finding and evaluation of exoplanets was directly attributable to precise astronomical techniques, tightly constrained by known physical laws (backed by a myriad of repeatable local and remote observations), to the extent which rules out other possibilities. (Ie: RV, transit, orbital brightness modulation, TV, microlensing, direct imaging, polarimetry and astrometry).

Name one demonstrated method for remotely detecting life over light-year distances, which can provide the same degree of consistency and constraint as the above. (Even SETI searches are dependent on the assumption that the target is transmitting under a myriad very specific conditional probability based assumptions, at the same instant of observation ... Compare this with a star/planet pair whose 'signal' can be precisely and repeatedly predicted!!)

The idea that 'the work and consideration' that led to exoplanet detection, and 'the work and consideration' that would lead to a hypothesised remote exo-life detection over light year distances are alike, simply doesn't take cognizance of the nature of the fundamental differences between the two problems.

Selfsim
2014-Feb-07, 08:09 PM
Right! And it's laughable that anyone ever thought the existence of planets in our solar system could have any bearing on the existence of planets elsewhere! Pure ideology! Unscientific thinking! The 'existence' of another instance of something already known to exist, can only established by empirical testing/verification.
What anyone thought about the 'existence' of exo-planets before testing/verification was merely anecdotal information.

Which leads me to think you didn't actually read the article. They were pointing out that true Earth-twins are unlikely, but that other worlds could have more widespread habitable areas, or be habitable for a longer period than the Earth likely will be.I choose to assign little weight to 'likely' or 'could'. These are opinions or beliefs .. nothing more. And I have obviously read the paper .. where do you think the quotes came from?

I have no idea why you'd think those are even connected issues.Then you must be the only person around these parts who hasn't learnt the lessons from the LR/PR/GEX Viking experiments and why they haven't been repeated by any probe since! You should read up on what Gil Levin has to say about this!

Noclevername
2014-Feb-07, 08:41 PM
The search for exo-life has become some kind of obsession, and has no place in a scientifically based, systematic exploration strategy of our planetary surroundings.


If science were pure and had unlimited funding, you'd be correct. But in order to gain access to resources, science also has to appeal to those outside the scientific communities. And so it needs a selling point. "What's out there?" is too vague. "Is there anybody out there?" gets people interested, gets the purse strings loosened. No, it doesn't cover everything. No one goal can. But appealing to our "are we alone" curiosity makes as good a starting point for directing our limited resources as any. And along the way, even if we never find any life, we'll pick up lots of useful information about the universe.

And who knows, we may even find life someday.

R.A.F.
2014-Feb-07, 09:07 PM
...we illustrate how tidal heating can render terrestrial or icy worlds habitable beyond the stellar HZ.

Sounds like the Nibiru "hotfoot". :D

Swift
2014-Feb-07, 10:09 PM
… Opinion based science … in its purest form!

I'm sorry, do you fancy yourself doing science here?
If you too can't leave out the snarky comments, I'll happily infract either or both of you

blueshift
2014-Feb-08, 12:20 AM
Science can grow without intention of seeing if we are alone. Many people are oriented more toward methodology than with reaching for the universe. To study how an auto operates I would take apart an old beater, see how its parts were arranged, and slowly rebuild it, replacing those parts that needed replacing. ( I even built a visible V8.) I would give it a test run in a controlled risk environment and the results would demonstrate whether I needed to rethink my steps or proceed to escalate the risk. The goal of getting the car or motorcycle to operate was only a minor detail because driving doesn't fulfill me. Watching dashed lines go by is a dreadful bore to me. Working on the project was neater. So I would look for other things to tear apart It is just that such a methodology takes one past the limits of cars and motorcycles into the universe whether someone who tinkers likes it or not.

Not all scientists got their start by dreaming about the universe, watching Carl Sagan and/or going to college. Some started by taking apart their tricycles, then the toaster, the TV, the radio, everything in the house and garage, always looking for more.

Noclevername
2014-Feb-08, 12:24 AM
Science can grow without intention of seeing if we are alone.

True, but it grows slowly without public support.


Not all scientists got their start by dreaming about the universe, watching Carl Sagan and/or going to college. Some started by taking apart their tricycles, then the toaster, the TV, the radio, everything in the house and garage, always looking for more.

That sounds like engineers more than scientists. :)

blueshift
2014-Feb-08, 12:32 AM
True, but it grows slowly without public support.



That sounds like engineers more than scientists. :)Good point that does describe many engineers -but it also describes science because the method is still there. Study, practical testing and restudy. The minute the Challenger blew up all the tradesmen I knew smiled at one another and said, "Looks like someone took a shortcut somewhere, trying to save a buck at all costs or making a deadline, and then proceeded to go ahead based on 'trust' or fear of being fired. Science can't be rushed. It has to have a firm grasp and understanding."

Noclevername
2014-Feb-08, 12:33 AM
Good point that does describe many engineers -but it also describes science because the method is still there. Study, practical testing and restudy. The minute the Challenger blew up all the tradesmen I knew smiled at one another and said, "Looks like someone took a shortcut somewhere, trying to save a buck at all costs or making a deadline, and then proceeded to go ahead based on 'trust' or fear of being fired. Science can't be rushed. It has to have a firm grasp and understanding."

Very true.

Selfsim
2014-Feb-08, 01:31 AM
If science were pure and had unlimited funding, you'd be correct. But in order to gain access to resources, science also has to appeal to those outside the scientific communities. And so it needs a selling point. "What's out there?" is too vague. "Is there anybody out there?" gets people interested, gets the purse strings loosened. No, it doesn't cover everything. No one goal can. But appealing to our "are we alone" curiosity makes as good a starting point for directing our limited resources as any. And along the way, even if we never find any life, we'll pick up lots of useful information about the universe.

And who knows, we may even find life someday.So you're saying the: "Are we alone?" quest is inauthentic ... a 'front' ... perhaps even a lie!?
And you say this is the way to gain the trust of those allocating resources?

The search is limited by what is technically achievable. There is no need for some inauthentic front 'excuse'. In fact such a 'front' simply detracts from the credibility of what science can achieve if allowed to proceed with intellectual honesty.

"Are we alone?" will be answered if "we are not alone". The question only introduces negative impacts on finding out, because it is an obvious diversion from science's key exploration/research aim. If I can see this plainly, then so can 'empowered others' ... Make no mistakes about it.

HZs are another diversion when applied beyond light year distances. Eg: if intelligent life actually does exist, the intellectually honest test strategy for discovering it is to scan the entire visible universe for intelligent signals. Developing the technologies capable of doing that, requires no artificial, intellectually dishonest, synthesised constraints, (under the guise of a concept like 'believed HZs'). This is also the way exo-planets were discovered ... they were not discovered because of some fantasy someone once wrote for a sci-fi movie, or by assuming they existed all along, (and by then attempting to re-write history to give the impression that 'the assumption led the way' all along!)

The OP paper demonstrates the arbitrary nature of the alleged constraint, referred to as 'Habitable Zone' (given their chosen definition of it).

Noclevername
2014-Feb-08, 07:08 AM
So you're saying the: "Are we alone?" quest is inauthentic ... a 'front' ... perhaps even a lie!?

I am absolutely not saying that. I'm saying that it makes as useful a goal as any. It is a long-range, open ended goal, but a goal nevertheless, and it gives us direction and a human, understandable motivation. The search is as useful as the find.



And you say this is the way to gain the trust of those allocating resources?

I'm saying people need something "big picture" to motivate them.



"Are we alone?" will be answered if "we are not alone". The question only introduces negative impacts on finding out, because it is an obvious diversion from science's key exploration/research aim. If I can see this plainly, then so can 'empowered others' ... Make no mistakes about it.

Then what would be your starting point to allocate limited resources point? And how would you convince the masses and the politicians they vote for that space exploration and examination is worth their time?



HZs are another diversion when applied beyond light year distances.

As I said, we have to start somewhere.



The OP paper demonstrates the arbitrary nature of the alleged constraint, referred to as 'Habitable Zone' (given their chosen definition of it).

Variable by condition does not mean arbitrary, and does not make them invalid as things to look at or for. Should we say "don't look at planets" because their definition has varied? No, no more than we should say "don't look for HZs". Yes, liquid water is a thing worth basing a definition around, even if water is liquid under a variety of planetary conditions.

Our definition of "outer space" can be considered arbitrary, as the Earth's atmosphere continues to thin out above that height and does not have any clear upper boundary. (Don't tangent on this one example, I don't want to derail.)

Now, I don't agree with A. DIM on most of his ideas, and I have no idea what the relative merits of this article are ("superhabitable" sounds like a meaningless buzzword to me; a world either has life or it doesn't, if it does then it's "habitable" by definition and if there's no life then it doesn't matter how nice the conditions are) but "follow the water" as general advice isn't bad advice.

Van Rijn
2014-Feb-08, 11:03 AM
Now, I don't agree with A. DIM on most of his ideas


Same here, but he's not the I would say that about (and I'm not implying you).



"superhabitable" sounds like a meaningless buzzword to me; a world either has life or it doesn't


They're talking about conditions important to life. So, for instance, a planet around a somewhat cooler star could have a stable temperature regime for billions of years longer than Earth. Or a planet could simply have greater habitable area than Earth. They go into a fair about of detail on their terminology they use for classification.

Van Rijn
2014-Feb-08, 11:30 AM
You need to re-read what I said.

They are attempting to counter the idea that Earth's specific Astrophysical environment is what the search should focus on.
Which is what I said.
(And what you just said, again).


Okay, I've read it again. What you wrote was dismissive, and did not appear to me to properly represent what was written in the article.


Name one demonstrated method for remotely detecting life over light-year distances, which can provide the same degree of consistency and constraint as the above.


Telescopes are improving constantly. The idea of finding exoplanets started really going into high gear about a decade before the first successful exoplanet discoveries, then started building up fast once the discoveries came through. Specialized telescopes like Kepler were developed to do mass screenings for exoplanets.

Now we're getting much larger telescopes, the James Webb space telescope, and after that probably a next generation visual range space telescope that will be able to directly image earth sized planets.

That's when we'll start seriously look for evidence of life in other solar systems.



The idea that 'the work and consideration' that led to exoplanet detection, and 'the work and consideration' that would lead to a hypothesised remote exo-life detection over light year distances are alike, simply doesn't take cognizance of the nature of the fundamental differences between the two problems.

I see no fundamental difference between the two problems. They both deal with physical processes that can be studied scientifically. Life is complex chemistry. Complex chemistry working on a worldwide basis can have detectable effects. We had initial difficulty finding exoplanets, and none of the existing techniques are considered exhaustive: It is virtually certain there are many other worlds they haven't detected even in the systems that have been studied. The point, however, is to find some exoplanets, and for some it is easier than others.

In these discussions, you seem to be so dismissive of arguments regarding ET life it seems like you are treating life as something that can not be evaluated scientifically - a type of magical thinking. You seem to just throw up your hands and declare impossibilities while others are going ahead and working the problem.

Van Rijn
2014-Feb-08, 12:03 PM
The 'existence' of another instance of something already known to exist, can only established by empirical testing/verification.


And considering what we know about the instances already known to exist to help guide and suggest future research is a reasonable action, and doesn't deserve your mocking dismissal ("Completely hilarious!").



What anyone thought about the 'existence' of exo-planets before testing/verification was merely anecdotal information.


People make hypotheses based on known science to help guide searches for exo-planets. I see no reason why that should be avoided here.



I choose to assign little weight to 'likely' or 'could'. These are opinions or beliefs .. nothing more. And I have obviously read the paper .. where do you think the quotes came from?


You conflated two different arguments and asked questions that could have been easily answered if you had read the paper. It looked to me like you might have skimmed the paper for terms that seem to annoy you, but it didn't appear you actually studied the arguments that were being made.


Then you must be the only person around these parts who hasn't learnt the lessons from the LR/PR/GEX Viking experiments and why they haven't been repeated by any probe since! You should read up on what Gil Levin has to say about this!

:rolleyes:

Completely missing the point. I have discussed the Viking experiments before in threads you were participating in, I'm quite familiar with them, and I certainly "learned the lessons" about doing those types of experiments in probes within the solar system.

No, the bit I didn't understand is why you thought this paper should have any bearing on doing repeats of Viking style life experiments in the solar system. Your comment appeared to be a complete non sequitur.

Local Fluff
2014-Feb-08, 01:23 PM
This thread has been totally derailed by the usual trolls and their personal problems.
I suggest that the moderator erase all comments after #1 and hope that it then could develop this very interesting TOPIC instead of the EGO of some trolls who spend too much time here.

captain swoop
2014-Feb-08, 03:00 PM
This thread has been totally derailed by the usual trolls and their personal problems.
I suggest that the moderator erase all comments after #1 and hope that it then could develop this very interesting TOPIC instead of the EGO of some trolls who spend too much time here.

If you have a problem with a post or poster then use the Reporting Triangle and report the post. Comments like this are not helpful. Do not attempt to moderate a thread yourself. Be Nice. Any more like this and you will be infracted. Take some time to read the Rules For Posting linked at the bottom of this post.

Noclevername
2014-Feb-08, 03:15 PM
So from what I understand of the paper, they are saying greater energy and stability make for a "more habitable" world; but I'm wondering if too much of a good thing can be a detriment.

Without occasional instabilities to prune out excess, the planet can become "clogged" with mutations that weaken the odds of species survival, and perhaps the survival of most life. Then when an actual extinction event does come along, WHAM, it hits far harder than it would to a planet with hardier biomes.

As for energy, I have been told elsewhere (http://cosmoquest.org/forum/showthread.php?147249-Chlorophyll&p=2168661#post2168661) that Earth plants don't use the most energetic light frequencies, in part because they are too energetic; they produce more waste heat than plant cells can stand. So perhaps a cooler planet would have better development than a hothouse.

Van Rijn
2014-Feb-09, 08:12 AM
Looking at my last two posts in this thread, I'd like to apologize for the tone in the posts. I do disagree on the issues mentioned, but I made the posts too personal.

iquestor
2014-Feb-09, 03:03 PM
superhabitable" sounds like a meaningless buzzword to me; a world either has life or it doesn't, if it does then it's "habitable" by definition and if there's no life then it doesn't matter how nice the conditions are) but "follow the water" as general advice isn't bad advice. 'super habitable' is probably not a good word for the intent, in my opinion. It just means conditions there for LAWKI are better than Earth's (based on what we know): More stable sun. Longer stable atmosphere, longer presence of liquid water. More stable axial tilt, Greater chance of radium and thorium which drives plate tectonics, etc. The thinking is that if conditions are just right for longer periods of time, the likelihood of life developing is greater.


So from what I understand of the paper, they are saying greater energy and stability make for a "more habitable" world; but I'm wondering if too much of a good thing can be a detriment.

Without occasional instabilities to prune out excess, the planet can become "clogged" with mutations that weaken the odds of species survival, and perhaps the survival of most life. Then when an actual extinction event does come along, WHAM, it hits far harder than it would to a planet with hardier biomes.

As for energy, I have been told elsewhere that Earth plants don't use the most energetic light frequencies, in part because they are too energetic; they produce more waste heat than plant cells can stand. So perhaps a cooler planet would have better development than a hothouse.

I would think Darwinian evolution would smooth these things out, its self-correcting in many ways. Instabilities come in many forms, and its the nature of evolution to constantly improve life forms and balance the biome. I doubt so much specialization would occur that life would be completely stamped out.


Habitable Zones: We base these on what we know, and that is fundamentally that LAWKI requires liquid water and an energy source, so we can place limits on a planets size and location to these constraints. We also strongly suspect that the presence of Radium and Thorium are essential to drive Plate tectonics, which is essential to the development of higher LAWKI life forms. There are a few other items as well.

Please note I said LAWKI, and not any Life. We cannot speculate well on what constraints NON-LAWKI HZs would have.

We look for LAWKI because that is what we would recognize.

We can detect life through spectroscopy; we have done it within our own solar system and there is no physical constraint on doing so with light years distance involved, if life does exist out there. It would be difficult, and very tedious, and doing so will likely require some luck in finding a target that is aligned well to reduce variables that could lead to errors. However it has been shown that we can detect CHON , Radium, Thorium, Water vapor and photosynthetic processes now, so better technology will allow us to do so is well within reason, and is expected within a few decades.

What if the photosynthesis on a target planet isn't like earth's? It doesn't matter, according to Dr. Garik Isrealian. If enough surface plants of microbes are converting their sun's light into energy, it will show up on a spectrum analysis.

Also if the spectrum shows the presence of artificial elements, i.e., impossible to occur naturally, then this is direct evidence of an industrial civilization.

Selfsim
2014-Feb-09, 08:39 PM
1. The Viking life detection experiments were capable of locally isolating samples of interest for direct testing purposes, yet they still returned ambiguity.

2. Remote exo-planet direct observation techniques have the same fundamental flaw. Ambiguity of results, (in terms of exo-life interpretation), will be the outcome. No remote spectrographic analysis of targets over light-year distances, can isolate or diagnose any specimen of interest. The necessary degree of confinement resolution for excluding false positive diagnoses of biology, is many orders of magnitude finer than any such remote observation can achieve, (physically or functionally), and is dependent on the nature of the target itself, (which by definition is undistinguished from its background environment, before any test is conducted). It is also dependent on our incomplete state of knowledge about undiscovered natural processes elsewhere in the universe.

3. So called 'Habitability Zone' definitions are thus a completely irrelevant concept for achieving such confinement resolution.

4. The idea of redefining 'Habitability Zones', (in the context of exo-life), is an obfuscatory diversion from the core principle of unbiased, non-premeditated exploration of all there is to explore (as opposed to a myopically focussed fixation on believed 'exo-life'). The development of fine resolution remote sensing technologies, capable of being repeatedly applied across all regions of the observable universe, on the other hand, can be guaranteed to return knowledge of the unknown within empirically measurable error constraints (irregardless of whether such targets might be life related or not).

5. The functional roles of the various Space administrations in the development of empirically sourced knowledge in science, goes way beyond the emotive belief that discovering aliens 'is of paramount importance'. Such a belief has no place in an exploration strategy of the observable universe.

Selfsim
2014-Feb-09, 09:07 PM
… We can detect life through spectroscopy; we have done it within our own solar system and there is no physical constraint on doing so with light years distance involved, if life does exist out there.We can detect elements and compounds through spectroscopy. Their sources (or causes) is a matter of interpretation. A proper test has to be capable of ruling out non-biological causes. We have almost no understanding of such 'causes' in order to do this, taken from from outside of Earth's immediate environment. Remote spectroscopy's application over light-year distances does not allow for the isolation of a specimen, which is a fundamental for distinguishing between biological signatures and a background environment.


It would be difficult, and very tedious, and doing so will likely require some luck in finding a target that is aligned well to reduce variables that could lead to errors. However it has been shown that we can detect CHON , Radium, Thorium, Water vapor and photosynthetic processes now, so better technology will allow us to do so is well within reason, and is expected within a few decades.What is capable of being detected is not the issue. What leads to the exclusion of other causes, is.


What if the photosynthesis on a target planet isn't like earth's? It doesn't matter, according to Dr. Garik Isrealian. If enough surface plants of microbes are converting their sun's light into energy, it will show up on a spectrum analysis.Basing an entire exploration strategy on the sole assumption that its target exists in the appropriately prepared form, (conducive to meeting the requirements of the test), is a futile waste of resources. This is the lesson learned from the Viking life tests.


Also if the spectrum shows the presence of artificial elements, i.e., impossible to occur naturally, then this is direct evidence of an industrial civilization.I may be prepared to concede my argument on this specific single scenario. It depends on being able to demonstrate that such a detection is repeatable, independently verifiable, and within measurement error bounds. The error limits must be sufficient to rule out all interpretive uncertainties and it is by no means clear how this can be done with an incomplete knowledge of natural processes throughout the observable universe.

Colin Robinson
2014-Feb-11, 03:08 AM
Superhabitable Worlds (http://online.liebertpub.com/doi/pdf/10.1089/ast.2013.1088)

Abstract:
To be habitable, a world (planet or moon) does not need to be located in the stellar habitable zone (HZ), and worlds in the HZ are not necessarily habitable. Here, we illustrate how tidal heating can render terrestrial or icy worlds habitable beyond the stellar HZ. Scientists have developed a language that neglects the possible existence of worlds that offer more benign environments to life than Earth does. We call these objects ‘‘superhabitable’’ and discuss in which contexts this term could be used, that is to say, which worlds tend to be more
habitable than Earth. In an appendix, we show why the principle of mediocracy cannot be used to logically explain why Earth should be a particularly habitable planet or why other inhabited worlds should be Earth-like. Superhabitable worlds must be considered for future follow-up observations of signs of extraterrestrial life. Considering a range of physical effects, we conclude that they will tend to be slightly older and more massive than Earth and that their host stars will likely be K dwarfs. This makes Alpha Centauri B, which is a member of
the closest stellar system to the Sun and is supposed to host an Earth-mass planet, an ideal target for searches for a superhabitable world.

Notions of "habitability" or "goldilocks zones" are ever-changing but they may be guiding us in the wrong directions in our searches for life elsewhere.

I'm of the opinion that just as earth-life has evolved and adapted to countless niches on this planet, so too would cosmic-life evolve and adapt to countless niches in this universe.

I think they're right to question the common assumption that present Earth conditions are optimal for life. As distinct from being optimal for present forms of Earth life, which are adapted to present Earth conditions.

A serious argument can be made that Earth of the Hadean epoch was actually much more life-friendly:

* plenty of volcanoes spreading nutrients around,
* plenty of solar energy reaching the surface in the form of ultraviolet light,
* temperature favoring formation of peptide bonds, making metabolism easy,
* and of course no atmospheric dioxygen to endanger the lives of anaerobic organisms.

Since then, it's been all downhill...

Noclevername
2014-Feb-11, 03:16 AM
Since then, it's been all downhill...

"You multi-celled, eukaryotic young punks get off my bacterial lawn!"

A.DIM
2014-Feb-14, 03:56 PM
I think they're right to question the common assumption that present Earth conditions are optimal for life. As distinct from being optimal for present forms of Earth life, which are adapted to present Earth conditions.


Agreed, it is "supposed to illustrate that a range of physical characteristics and processes can make a world exhibit more benign environments than Earth does. Given the amount of planets that exist in the Galaxy, it is therefore reasonable to predicate that worlds with more comfortable settings for life than Earth exist."

One thing we know for certain is that life adapts to and survives myriad previously-thought-and-so-called "hostile" environments. I see no reason to assume life in the universe could not do the same and so any alleged "habitable zone" is the universe at large, in my opinion of course.

Noclevername
2014-Feb-14, 05:42 PM
One thing we know for certain is that life adapts to and survives myriad previously-thought-and-so-called "hostile" environments.

By that very same logic, then, calling a world "super-habitable" is a misnomer; life adapts to its environment, therefore any environment with life is habitable.

publiusr
2014-Feb-15, 08:20 PM
Well, maybe not super-habitable. But if (intelligent) life developed on a moon of a gas giant, they would have a lot more toys to look at suspended over their bed as it were to play with and get spaceflight started earlier...so super quickstarting maybe?

Colin Robinson
2014-Feb-15, 10:08 PM
By that very same logic, then, calling a world "super-habitable" is a misnomer; life adapts to its environment, therefore any environment with life is habitable.

Life adapts, but are there not specific places on Earth (such as rainforests and coral reefs) where living things are especially abundant and diverse? What word would you use for a planet where biomass and biodiversity are substantially more than Earth's?

Noclevername
2014-Feb-16, 02:14 AM
Life adapts, but are there not specific places on Earth (such as rainforests and coral reefs) where living things are especially abundant and diverse? What word would you use for a planet where biomass and biodiversity are substantially more than Earth's?

I'd call it terrific. Got one?

There have been times when Earth has been such a world, far more full of life than it is today. There have been times where it's been almost wiped clean of life. It's still the only one we know of that's inhabited. Until we come up with other actual life-bearing worlds, calling something "habitable" is guesswork at best.

Colin Robinson
2014-Feb-16, 06:15 AM
I'd call it terrific. Got one?

I've made no such claim, and neither do the authors of the paper mentioned in the OP.


There have been times when Earth has been such a world, far more full of life than it is today. There have been times where it's been almost wiped clean of life. It's still the only one we know of that's inhabited. Until we come up with other actual life-bearing worlds, calling something "habitable" is guesswork at best.

Making educated guesses, and testing them, is an important part of how science moves forward. Karl Popper used the phrase "conjectures and refutations".

Paul Wally
2014-Feb-16, 07:53 AM
Life adapts, but are there not specific places on Earth (such as rainforests and coral reefs) where living things are especially abundant and diverse? What word would you use for a planet where biomass and biodiversity are substantially more than Earth's?

I'd call such a planet "super-inhabited". "Habitable" is the potential to support life, but this leads to a problem: What if different planets are habitable to different kinds of life? For example, Titan could be habitable to a different kind of life than Earth-like life. That's why I think it is best to define habitability, for the time being, as the potential to support Earth-like life, because for this we at least have a set of testable criteria like liquid water, CHON and so forth.

Though I think the notion of "super-habitability" is an interesting concept, I also think it would apply more naturally to solar systems than to individual planets. A super-habitable solar system would be a solar system with a high potential (probability) of hosting a habitable planet in terms of our criteria for habitability.

Noclevername
2014-Feb-16, 10:24 AM
I've made no such claim, and neither do the authors of the paper mentioned in the OP.
Never said you had. But my point is that with only one example of an inhabited world, we can't call anything else habitable yet.



Making educated guesses, and testing them, is an important part of how science moves forward. Karl Popper used the phrase "conjectures and refutations".

Yes. That has nothing to do with what I said, but I completely agree with the concept. I was talking about terminology.

iquestor
2014-Feb-16, 02:21 PM
Quote Originally Posted by iquestor

What if the photosynthesis on a target planet isn't like earth's? It doesn't matter, according to Dr. Garik Isrealian. If enough surface plants of microbes are converting their sun's light into energy, it will show up on a spectrum analysis.
Basing an entire exploration strategy on the sole assumption that its target exists in the appropriately prepared form, (conducive to meeting the requirements of the test), is a futile waste of resources. This is the lesson learned from the Viking life tests.


Selfsim wrote:
Basing an entire exploration strategy on the sole assumption that its target exists in the appropriately prepared form, (conducive to meeting the requirements of the test), is a futile waste of resources. This is the lesson learned from the Viking life tests.

My understanding is that detecting alien photosynthetic processes wont be an assumption. Most earth photosynthetic processes occur at wavelengths that are highly optimal based on the light spectrum of our sun. This isn't an accident, it's Darwinian evolution. The spectral signatures of these processes is therefore predictable, and do not align with chemical non-biological signatures. Dr. Isrealian's point is that IF alien photosynthetic processes are abundant on planet, we can predict what their spectral lines would be, based on their stars light. This would be corroborated by detection of CHON and water vapor, as well as a seasonal variation of the photosynthetic lines discovered. While I agree it couldn't be 100% because there is an outside chance its produced by something we have never encountered, but if such spectral lines were predicted and discovered with the corroborating evidence, most scientists would conclude the most obvious reason would be life and photosynthetic processes.


Basing an entire exploration strategy on the sole assumption that its target exists in the appropriately prepared form,
That's not the entire exploration strategy, its one exploration strategy that we can apply to hundreds of thousands of stars. And the NULL result is as useful as the positive result. You seem to suggest we don't even try. It's either out there, or its not. We wont find it if we don't look.

SETI is looking for a far thinner needle in a much bigger haystack.

Selfsim
2014-Feb-17, 12:26 AM
… My understanding is that detecting alien photosynthetic processes wont be an assumption.And that: 'photosynthesis exists elsewhere', to detect, isn't eh?
Most earth photosynthetic processes occur at wavelengths that are highly optimal based on the light spectrum of our sun. This isn't an accident, it's Darwinian evolution. And that: 'Darwinian Evolution is a universal phenomenon' isn't also an assumption?
The spectral signatures of these processes is therefore predictable, and do not align with chemical non-biological signatures.And the test has been shown to be capable of discriminating between 'biological and non-biological spectral lines' over light year distances, when aimed at a varying phenomenon, whose variability is relative to measurables normalised to local observations of only Earth ... to the extent that all other explanations pertinent to that target can be eliminated, eh?

Where is the evidence for how this can be accomplished?

Dr. Isrealian's point is that IF alien photosynthetic processes are abundant on planet, we can predict what their spectral lines would be, based on their stars light.If the discrimination between 'bio- and non-bio spectral signatures', over light year distances, was somehow shown to be measurable to within the same precision as it is in Earth's case, then extrapolation of the idea might at least have some physical basis.

But alas, there is no evidence that it can be.

How has he calculated the error bars on his 'prediction'?

This would be corroborated by detection of CHON and water vapor, as well as a seasonal variation of the photosynthetic lines discovered. While I agree it couldn't be 100% because there is an outside chance its produced by something we have never encountered, but if such spectral lines were predicted and discovered with the corroborating evidence, most scientists would conclude the most obvious reason would be life and photosynthetic processes.What is 'outside chance'?

So, the correlation of a photosynthetic 'signature spectrum' along with CHON and water, is sufficient evidence to eliminate all other explanations for a measurement which has not yet been observed elsewhere, and consensus is a sufficient means for eliminating them?


That's not the entire exploration strategy, its one exploration strategy that we can apply to hundreds of thousands of stars. And the NULL result is as useful as the positive result.How are false positive and false negatives to be eliminated, so as to render the test reliable?


You seem to suggest we don't even try. It's either out there, or its not. We wont find it if we don't look.

SETI is looking for a far thinner needle in a much bigger haystack.What I'm saying is that exploration of accessible (reachable) goals where verification/falsification is practically feasible and demonstrable, is a worthy principle for basing a strategy on.

Show me how the inherent Type I and Type II statistical errors can be eliminated over light year distances, and I might buy in. Otherwise, the 'strategy' is all based on nothing more than conjecture and belief.