Inhabitable Zone

[Tormod]

cwes and alxian, you are discussing two completely different things. I suggest alxian takes his ideas into a new thread, since they are about requirements for civilisations rather than the emergence of life (forgive me if I'm mistaken).

[cwes99_03]

I believe you are mistaken only in your definition of habitable. I understood the connotation to be on the grand scale of habitability. While some life form, say a few bacteria, or even that methane wolly bear worm that lives deep in the frozen methane under the sea, may survive the harsh climates, alxian points out that large civilization type of habitability requires more. Humans are the only animal so adapted to extremes that they can build themselves vast fortresses from the elements and live in nearly uninhabitable regions (say on a space station) where they normally could not survive.

As for a region where life easily evolve as the theory would suggest, it would take much less extremes to create a great biome.

[Tormod]

I believe you are mistaken only in your definition of habitable. I understood the connotation to be on the grand scale of habitability.

 

I must admit I find your argumentation convoluted - I am not sure what you are trying to say.

 

You wrote (previous page):

 

The habitable zone for the earth is fairly narrow. I believe that if the orbit of the earth were to take it more than 1% further in orbit than it currently does, there would only be a habitable zone on the earth of about +/- 22 degrees north and south of the equator

 

...which I refuted.

 

I don't see how this has anything to to with my definition of habitable. I am trying to stay on the topic of whether the actual orbital parameters of the Earth are so narrow that a small change would put us outside of the habitable zone - to which my response is "no".

[cwes99_03]

Does anyone know how wide the Inhabital Zone is for our Solar System?

 

Considering it freezes at the poles, and gets fairly hot at the equator, the inhabital zone must be fairly fine tuned, because doesn't this suggest that if earth was 'the radius of earth' further away there would be ice around the equator?

Based off of this post, I made my assumptions on habitability. You obvoiusly made some assumptions based off of something else as to your definition of habitability. I do not refute your point that many organisms can live in much harsher climate, thus widening the "habitability" zone considerably. I do not refute your idea that simply increasing the average radius of the earth's revolution around the sun would not be enough to greatly change the overall climate of the earth, though there would be a noticeable effect considering they can tell a mean temperature change of half a degree.

I do only post that increasing the average radius of the earth's revolution around the sun would significantly chance the climate. By significant I mean that humans would be uncomfortable in such a climate and on a large scale would choose to call these new regions of the earth that are regularly sub-zero uninhabitable. In this post, I am not allowing you to significantly change the makeup of the earth or anything else that I hold constant, only the average distance of the earth from the sun. I don't see your problem with this.

[alxian]

indeed tormod is right i should make another thread, and did, but it was ignored

 

what i was trying to say is that LHZ, life habitable zone, is as credible as phrenology. its not useful for modern science to consider an LHZ because life can survive pretty much anywhere. it just needs large enough area for simple life to flourish and more complex life to bud off from. self renewing energy systems life can slip into with ease and an abundance of raw resources. the planet itself is much more important than its proximity to a star. all an LHZ is good for is determining how much ambiant energy reaches a planet encouraging the proliferation of simple life forms. since simple life forms flourish essentially regardless of sunlight oxygen etc, the question isn't how much ambiant solar energy reaches life, the question is how complex life will become in a particular environment.

 

rather than considering solar radiation and water as the basis for life we should instead consider available resources. it should be assumed life will exists if there are enough self replenishing energy conversion systems. as long as energy flows through a system of abundant resources life probably could take advantage of excess energy. generating new chemicals in the process but in such small amounts it doesn't affect the larger energy system until those waste products themselves become abundant. and as long as a resource in the existing system is not exhausted energy will continue to flow. the more energy that is available in a given system the more life can take advantage, depending on the efficiency and the waste products a particularly rich system will sustain more life. the richer the system the more varieties of life can be sustained. thus the more energy that is moved through a very large and efficient system the more likely life will survive and evolve.

 

earth also has many niches life can occupy, while most other planets do not.

 

if you take a look at the earth you'll notice, according to the record, life on earth, at least the interesting varieties needed HUGE niches before they become stable. then more complex lifeforms evolved and they required HUGE niches.

 

the spice of life is size (of the environment) stability (of existing energy system) and variety (of raw resources)?

 

earths atmosphere (created by the life processes of promordial abundant life forms) and its interaction with the oceans creating weather renews many systems with raw resources while purging them of toxins. perhaps the single most important thing for life to survive to thrive is ceiling itself off from the toxicity of space in a semi permiable shell of atmosphere, that lets in some energy while blocking out other types. the question isn't can it happen again, because the particularities of our atmosphere is the result of adaptations of life on earth, other very different abundant simple lifeforms will form their own particular atmospheres. but the ability to create an atmosphere at all depends on the ability for abundant simple life to be able to source the materials from the planet. so again the bigger and richer the niche the more potential there is for life to create and sustain a productive shell of atmosphere then adapt to it once its in place.

 

which is yet another knock against an arbitrary zone where life can begin because earth did not automatically form its atmosphere, life created it then adapted itself to it. so it helps if the star radiates in a wide spectrum. life will adapt to it and thrive if enough ambient energy penetrates the shell that needs to block toxins. where the planet is is irrelevant as life will adapt itself to the new conditions gourging itself on a higher influx of free energy thus thickening the atmosphere with higher exhaust, or if further away thinning the atmosphere to let more light in but still moderating the toxins. too much toxin and life dies.

 

life on a planet far from the sun, inside a giant gaseous mass or a rocky mass or ice ball will also probably be dormant (wether it forms there from the heat of formation or dormant having formed elsewhere) because there isn't enough flowing energy or raw resources to convert to maintain lifes processes (which can be very simple or extremely complex). a possible source of energy is the heat from radiocative decay unfortunately that type of energy is generally toxic, some creatures may still be able to survive if they have so adapted.

 

another factor for life is time. given very high stabililty in an particular system life may have no need to evolve. say the clouds of jupiter. it would take very long time for life to saturate that system, so long in fact that even if microbes have saturated the clouds they move so quickly that more complex chemicals formed by those microbes like the refinement of sulphur into acids, those acids will take ages to reach a meaningful level for more complex life forms to take advantage of in their metabolisms. even longer if the acids are heavier and cleaned right out of the microbes biomes. if those acids settle into a particular cloud depth and those microbes haven't adapted to the toxin they'd be destroyed. also since the clouds are constantly being stired a storm could easily stir the acid wiping out huge swathes of microbes. but generally life has some level of immunity from its waste products.

 

also when you get bigger environments with tons of materials and systems with huge potential for energy conversions you'll see life taking hold with high variations occupying any space where excess energy can be captured and used. the higher the variety of resources the more systems are possible. the bigger the size of the biome the higher the potential for life to flourish, simple animals surviving on the most basic abundant and stable energy conversion systems. given time and the production of ever more complex materials the higher the potential for life to become more complex.

 

as long as the resources are in high enough abundance the longer the simple life forms will survive. depending on the diversity of resources adaptation/evolution will result in more complex life forms enhabiting the stable niche where the resources the require can be sourced and their wastes purged. if anything happens to the simple life forms upon which the more complex life forms depend for resources then they will die off unless they can adapt or have no dependencies on those simple creatures. it may be that initially a limited supply of a specific resources causes the periodic rise and fall of evolved species. as long as their adaptations are not lost or too complex to happen again when the resource is renewed the adaptations resurface. the simple life forms continue to prosper but the more complex evolved life forms will disappear and reappear. it could be that simple life forms don't move around much but more evolved creatures help to expand lifes foothold in a particular environment. when they (more complex animals) die off the process of evolution has to start over but there is an ever increasing abundance of simple life forms to speed up the process. so initially evolution is extremely slow but eventually as systems stabilize and expand ever more complex life forms appear in higher abundance.

 

the quesiton then would seem to be not where should a planet be, or what specific ingredients are required, but how stable a system is and how much diversity is there of resources and niches. beause a system can be as rich as can be with resources for simple life but if most of them are toxic to any adaptation evolution will not immediatly occur.

 

a lack of toxins and an over abundance of energy greatly encourages the development of huge niches. the slow addition of toxins or life adapting to more complex energy conversion system encourahes new forms of life to take hold. as long as those new systems are not toxic and can merge into existing systems then those new life forms will prosper. but the more complex life gets the more energy it needs. so while simple life can explode in a particular environment and survive for billions of years unless there are more complex niches possible life will not evolve.

 

so where LHZ theory maintained that a planet needed to be snug in the middle of a stars LHZ for life to gain a toe hold (which essentially meant scum saturating the earths oceans) it turns out that earth actually was almost not in the suns LHZ and life can survives virtually anywhere. life survived by creating a shell from space and them filling out the innumerable niches creating all forms of new life with all kinds of new chemicals produced from their wastes feeding other niches while poisoning others. time passed and niches stabilized into systems. all the while though those initial abundant resources are not yet exhausted.

 

if life hadn't evolved to use the new abundant resource, such as oxygen it could have been poisoned... good thing life was already abundant enough that it was able to adapt and flourish.

 

also you have to consider the LHZ is calculated based upon earths early toxic atmosphere before life started filling it with oxygen. if it was thicker the LHZ for earth would be different. or is life failed to adapt to oxygen it would never have survived.

 

thus other planets with other concentrations of raw materials could still be bastians for life outside of earths particular LHZ and would be toxic to life if they were in earths particular orbit. as long as life has the time to adapt to its constituants probably any raw atmosphere can be adapted to support a rich thriving biosphere.

 

so

 

and until we know what ingredients are need for massive atmosphere modifying amounts of simple life to form in the first place and then saturate a niche like the oceans we can't really be sure what an LHZ really is. all we know is they need tons of energy.... which the star provides but which their exhaust mollifies until enough toxins are blocked for life to continue to flourish.

 

LHZ = bunk

 

what complex lifeforms require are VERY large niches that are high in raw and refined resources that can quickly be purged of toxins as well as the ability to move between those niches efficiently. an abundance of water and a weather system granted by the atmosphere helped life on earth generate and sustain all those niches. the same possibly could happen in the clouds of venus and jupiter but those niches lack static niches... places where life imported or spontaneoulsy generated from complex chemical reactions can gain a toe hold in the first place.

 

the ocean for instance presents life with a low toxicity niche with an abundance of energy (from the sun and from the heat of the earth) and raw chemical materials for energy conversion of simple chemicals into more complex chemicals. which is funny because the more complex chemicals there are the more niches will allow life to convert complex chemicals to simple ones. life can thus use fission and fusion to source energy just in very small quantities and without very high efficiency.

 

i'm thinking it may actually be possible to extrapolate the forms life could take based mostly on the available raw materials and possibly for simple life forms to move between environments. it would be impossible to tell what physical form life would take but assuming a planet had the right materials and available abundance of energy it should be possible to guess what systems life could adapt itself to.

[lindagarrette]

If life had not begun way back when, what are the prospects it could take hold right now?

[alxian]

take hold or spontaneously spring to life

 

 

its been shown that complex amino acids can be created from sterile culture

 

if we had a way to see what becomes of those amino acids we would be able to say with certainty life can begin spontaneously from those ingredients.

 

those ingredients that are not exactly ubiquitous but neither unique to earth.

 

once the amino acids rippen into a simple creature and adaptations begin.... are those adaptations radom or predictable given the available resources?

[cwes99_03]

Ah nice to know you site studies that say that the atmosphere and ionic charge of the this occurence had to be one in billions of chances to produce just a small amount (microscopic really) of viable amino acids, and that if this occurence were to take place, the area would be so volatile that as soon as they were created they would also likely be destroyed.

Not to mention that in order for these things to take place, ambient temperatures would have to be right in the range of those of earth.

 

LHZ is simply a theory based upon observable information on earth. If information on other planets with life were to become available then more information then this theory would definitely be fleshed out quite a bit. Until that point however, we are the only known planet with life and civilization on it.