Life as we know it?

[Moontanman]

Is "life as we know it" common in the universe or is "life as we know it" an oddity of the Earth and it's charmed environment?

 

At some point the organic chemical bath of various chemical reactions, some replicating and some simply making the molecules necessary for replication came together to form a cell and these cells combined the chemical reactions that had been going on independently in the surrounding ocean and incorporated them into what we would recognize as a reproducing cell or "life as we know it". (shopping bag theory of life)

 

Was this first cell inevitable? Or was it the result of the Earth's environment providing an unusually long span of time for the chemical reactions of life to come together to form a cell. Or was it an oddity that seldom if ever arises on a planet. Will we find planet after planet with oceans covered only by oily organic chemical systems with nothing we would recognize as "life as we know it"?

 

It is my contention that the Earth was alive before the first cell as a an entire ocean of metabolizing chemicals. Also that this is the natural state of "life" and that the more advanced "cell" form of life is an oddity that may very well never come into being anywhere else.

[Boerseun]

Whether "Life as we know it" is prodiguous in the universe is, indeed, a question for the ages. And one for which we simply don't have an answer.

 

But we can speculate.

 

And I'm of the opinion, that given the complexities of organic chemistry, and the seemingly endless combinations possible with carbon, hydrogen and nitrogen, if you have an Earth-like planet roughly the same distance from a sun-like star than we are, with roughly the same mix of chemicals found on Earth, and a few billion years to play with, then, yes - life as we know it is inevitable. But that's just my opinion.

 

Earth-like planets are hardly the norm. Heck, look at our own solar system. The norm seems to be gas giants existing in a deep freeze. Which might make other life-forms possible based on other chemistries, totally foreign to what we are used to. Silicon might take the place of carbon, producing such strange lifeforms that we might not even recognize it as such. Which might very well mean that Earth-like life is the exception - carbon-based life might be a shortcut, coming into existance in the hectic inner regions of solar systems which are awash with plentiful energy, where species' lifetimes are measured in millions of years, whereas silicon-based lifeforms come to the fore in the more stable outer regions, where species' lifetimes are measured against the ages of stars.

 

I dunno, really. We can merely speculate, given the evidence. But, I'm a bit of a carbon-chauvinist, myself. And as crazy as organic chemistry appears on Earth, it'll be equally crazy and full of potential on any other planet, given the right conditions.

[Moontanman]

My point is that life doesn't have to be a cellular machine with DNA and RNA that has the potential to become complex. Life was a world wide complex of interacting chemicals, I see no reason to expect life to always or ever advance to the cellular level. a less than stable environment would be enough to cause life to remain at the less complex stage for the entire life time of a planet. so many unlikely things go into making the earth a stable environment for life as we know it I don't see any reason to expect it to happen with any regularity anywhere else.

[Donk]

Life as we know it depends first and foremost on liquid water. That gives a very narrow temperature range. But in that narrow temperature range, water on rock will give Moontanman's stew of interacting chemicals; from there it's likely that one will hit on a way of growing by absorbing nearby chemicals and then replicating itself.

 

Once that stage is reached, the rest becomes inevitable. At first the chemicals have an endless supply of building materials, but eventually they get used up. Then the proto-life chemicals start on each other - dismantling rivals, absorbing them, replicating. Those chemicals that do it best make more replicas. That's the start of the ongoing arms race called Life, which is continuing through us and will end who knows where?

 

If "life as we know it" means land life, and intelligent land life at that, it seems a lot less likely. The Earth managed for most of its history without any land life, and tool-using animals are very recent indeed. I like the theory that early land life was swept ashore on high tides and managed to learn how to survive without constant immersion in water. Without our oversized moon, there would be no tides. Life wouldn't have the same incentive to colonise the land, and it might have taken many billions more years, if ever.

[DI5STURBED]

Moontanman,

This is one of the questions I find most fascinating, seeing as there are so many different answers too it. I think a good start may be the anthropic principle, which states the we should take into account the set of constraints that can support human life. With that we can say that if there was only one universe ever made than the way it develops and the formation of planets and life for that matter was not random at all. Since the universe the anthropic principle is talking about is one that revolves around us, and why shouldn't it? We do exist.

 

Another way of looking at it is that all of this is completely random and that we are a fluke happening on chance alone. This may not be far from the truth, in science a lot of things are left to chance; quantum theory, probability for a chemical reaction, the weather, So why should we be so special and not just as random as everything else?

 

As for life on other planets I don't believe it is looking too promising since I believe only Mars and Titan have the organic compounds to support life. Although there is no reason that a different form of life that doesn’t need organic compounds to survive shouldn't exist. Personally I am an optimist and believe that there is some other form of life out there just because we haven't found life elsewhere in our little sliver of the universe we call the solar system doesn’t mean there isn’t life in this huge still expanding universe.

[Moontanman]

Life as we know it depends first and foremost on liquid water. That gives a very narrow temperature range. But in that narrow temperature range, water on rock will give Moontanman's stew of interacting chemicals; from there it's likely that one will hit on a way of growing by absorbing nearby chemicals and then replicating itself.

 

This act of reproduction was already going on before cells formed.

 

Once that stage is reached, the rest becomes inevitable. At first the chemicals have an endless supply of building materials, but eventually they get used up. Then the proto-life chemicals start on each other - dismantling rivals, absorbing them, replicating. Those chemicals that do it best make more replicas. That's the start of the ongoing arms race called Life, which is continuing through us and will end who knows where?

 

The chemical pathways of chemosynthesis were already present and producing ever more chemicals for other reproducing chemicals to feed on. Even photosynthesis was already present in the soup of interacting molecules. Most all the things that go on inside cells today were already present in the world wide sea of organic chemicals both dissolved and floating on the oceans of our planet.

 

 

If "life as we know it" means land life, and intelligent land life at that, it seems a lot less likely. The Earth managed for most of its history without any land life, and tool-using animals are very recent indeed. I like the theory that early land life was swept ashore on high tides and managed to learn how to survive without constant immersion in water. Without our oversized moon, there would be no tides. Life wouldn't have the same incentive to colonise the land, and it might have taken many billions more years, if ever.

 

"Life as we know it" in my definition is cellular life, from bacteria on.....Once the level of bacteria was reached even more "charmed" aspects of our planet come into play. what I am questioning is the idea that cellular life is inevitable once the world wide soup of living chemicals is under way.

[Moontanman]

Moontanman,

This is one of the questions I find most fascinating, seeing as there are so many different answers too it. I think a good start may be the anthropic principle, which states the we should take into account the set of constraints that can support human life. With that we can say that if there was only one universe ever made than the way it develops and the formation of planets and life for that matter was not random at all. Since the universe the anthropic principle is talking about is one that revolves around us, and why shouldn't it? We do exist.

 

Another way of looking at it is that all of this is completely random and that we are a fluke happening on chance alone. This may not be far from the truth, in science a lot of things are left to chance; quantum theory, probability for a chemical reaction, the weather, So why should we be so special and not just as random as everything else?

 

As for life on other planets I don't believe it is looking too promising since I believe only Mars and Titan have the organic compounds to support life. Although there is no reason that a different form of life that doesn’t need organic compounds to survive shouldn't exist. Personally I am an optimist and believe that there is some other form of life out there just because we haven't found life elsewhere in our little sliver of the universe we call the solar system doesn’t mean there isn’t life in this huge still expanding universe.

 

I ascribe to the idea that life is a natural occurrence that will come about any time the correct conditions come together.

 

Our own solar system is probably not full of cellular life other than the Earth. Mars is too small to really retain an atmosphere capable of allowing the metabolism first hypothesis to work. If we find cellular life on Mars them my idea of a planet awash with metabolisms with out cells is obviously false.

 

Titan on the other had is perfect for silicon life using liquid hydrocarbons as a life fluid. Possibly when we go there we will find an entire planet awash in metabolisms but no cells. If so this would lend credence to my suggestion.

 

I'm sure I will not live long enough to know details about planets on other stars other than the fact they exist but the more we visit the more data points we will have on the curve.

[Donk]

"Life as we know it" in my definition is cellular life, from bacteria on.....Once the level of bacteria was reached even more "charmed" aspects of our planet come into play. what I am questioning is the idea that cellular life is inevitable once the world wide soup of living chemicals is under way.

Once the arms race is under way, the living chemicals have a lot of different things to do: defence, attack, digestion/growth, replication. This implies a cell wall to contain and protect the different parts of the organism: hence, cellular life - voila!! :rolleyes:

[Moontanman]

Once the arms race is under way, the living chemicals have a lot of different things to do: defence, attack, digestion/growth, replication. This implies a cell wall to contain and protect the different parts of the organism: hence, cellular life - voila!! :rolleyes:

 

Why does this imply cell walls? You have metabolizing chemicals producing all the raw materials the reproducing chemicals need, why bother with cell walls? What would the incentive be to cause cells to have an edge over free roaming chemicals? Cells had to figure a way to allow certain chemicals in and allow others out with out allowing the wrong ones in or out. Sounds like a lot of trouble when free roaming chemicals were already reproducing everywhere with no bounds or limits, exploiting new chemical pathways, able to be there to reap any and all necessary chemicals.

[Donk]

Why does this imply cell walls? You have metabolizing chemicals producing all the raw materials the reproducing chemicals need, why bother with cell walls? What would the incentive be to cause cells to have an edge over free roaming chemicals? Cells had to figure a way to allow certain chemicals in and allow others out with out allowing the wrong ones in or out. Sounds like a lot of trouble when free roaming chemicals were already reproducing everywhere with no bounds or limits, exploiting new chemical pathways, able to be there to reap any and all necessary chemicals.

You're postulating a single chemical able to do all the things I posted above: defence, offence, digestion/growth, replication. I'm suggesting that a community of specialised chemicals held in place by a cell wall would be able to outcompete the single-chemical forms and would therefore supersede them over time.

[Moontanman]

You're postulating a single chemical able to do all the things I posted above: defence, offence, digestion/growth, replication. I'm suggesting that a community of specialised chemicals held in place by a cell wall would be able to outcompete the single-chemical forms and would therefore supersede them over time.

 

No, I'm suggesting a lots of different chemicals doing everything a cell can do but outside a cell in solution. Lots of different metabolisms all doing their own thing as each uses the results of other reactions in it's own reactions. with chemosynthesis and photosynthesis operating in this solution to provide a continuous source of chemicals to feed the other reactions. This is called the metabolism first theory.

 

What I am suggesting is that there was no reason to expect cells to arise in this sea of chemicals. Cells would have been an oddity with no connection with the initial formation of life. Something must have given these cells some advantage over the free floating chemicals or cells were an accident that may not happen in most or any other planetary life.

 

The problems connected with cells would have been over whelming until cell walls that could differentiate between the chemicals that needed to come in the cell and chemicals that needed to stay out and chemicals that needed to leave and chemicals that needed to stay. Three maybe four steps away from the life soup and all of them needed to make a cell work.

 

Either there was some real and obvious reason cells needed to form or cells were an accident. I honestly can't think of a reason cells would be better than the living soup so that leaves accidental formation. I'm betting at the very least it took much longer to form cells than it did to form a living ocean of chemicals.

[Eclogite]

Either there was some real and obvious reason cells needed to form or cells were an accident.

There may be a real and obvious reason.

 

NASA scientist Dr Jason Dworkin and his team from the SETI institute were able to create bubbles of material with the appearance of cells. They did this by taking mixtures of ices, with compositions comparable to those thought to be commonplace in interstellar space, and bombarding them with ultra-violet radiation. When immersed in water, droplets +/-10 micro-m with an inner and outer layer formed.

 

A team of scientists from Oxford, University of Colorado and the National Oceanic and Atmospheric Administration postulated an important role for aerosols. These tiny droplets form as water evaporates from the ocean and may remain suspended in the atmosphere indefinitely. Today there is a significant content of organic material present in such droplets. Some of this material coats the outer surface of the particle. Evaporation increases the concentration of organics, while collision with meteoric dust could provide metallic elements. The droplets are exposed to a variety of temperature and radiation conditions that might promote chemical reactions.

The size, organic coating, and salinity that differs from sea water are all features of the particles shared by the simplest, prokaryote life forms, such as bacteria.

 

In short, it may be that a cellular structure is a pre-requisite for providing adequate concentrations of pre-biotic chemicals to allow auto-catalytic metabolisms to emerge.

 

[Note: I've lifted these comments (middle two paragraphs) from a working document of mine on the Drake equation. I think they are my own words paraphrasing the original articles, but they might be condensations from popular accounts at the time.]

[HydrogenBond]

Life as we know it requires water. No enzyme, DNA or RNA can work with any other solvent, nor do any of these work very well in air. Based on these simple observations and basic logic water is essential to life as we know it. The question becomes, what is there about water that gives water special properties needed for life? It has to do with hydrogen bonding, that same variable that is also important to bio-molecules. Simple logic would say maybe there is a connection, with life evolving hydrogen bonding because it is also important to water. This seems like the smartest way to extend the unique properties of water to life.

 

This connection does not discount the existing mechanisms for life. But what it suggests is these mechanisms are not complete since they leave out a variable which can be shown to be essential to all biological activity. In other words, let us take an enzyme and express its mechanism. Next, we will dehydrate it to see if the enzyme still holds true to that mechanism. Obviously it won't, so this mechanism does not tell the whole story.

 

Let me give an analogy for biology. We have a child learning to ride a bike with their dad (water). He is helping by holding the bike. What we do is concentrate all our attention on the child and bike, and ignore the dad and try to correlate the ride of the child out of the context of the dad. Even though the child won't even get going without his dad, dad is not important. We will assume somehow the child spontaneously gets going with a certain random magic. It has nothing to due with dad helping to hold up the bike or give a push. That is common wisdom in a nut shell. To move things into the future, we need to do it the hard way and include all the variables. I realize the old way is easier, but the future way is more logical and scientific.

 

Once we advance the old fashion way, when questions are asked like, life as we know it, the answers will become more modern and less philosophical. Right now the theory opens the door to almost anything because of the all the unknowns, including dad.

[Moontanman]

There may be a real and obvious reason.

 

NASA scientist Dr Jason Dworkin and his team from the SETI institute were able to create bubbles of material with the appearance of cells. They did this by taking mixtures of ices, with compositions comparable to those thought to be commonplace in interstellar space, and bombarding them with ultra-violet radiation. When immersed in water, droplets +/-10 micro-m with an inner and outer layer formed.

 

A team of scientists from Oxford, University of Colorado and the National Oceanic and Atmospheric Administration postulated an important role for aerosols. These tiny droplets form as water evaporates from the ocean and may remain suspended in the atmosphere indefinitely. Today there is a significant content of organic material present in such droplets. Some of this material coats the outer surface of the particle. Evaporation increases the concentration of organics, while collision with meteoric dust could provide metallic elements. The droplets are exposed to a variety of temperature and radiation conditions that might promote chemical reactions.

The size, organic coating, and salinity that differs from sea water are all features of the particles shared by the simplest, prokaryote life forms, such as bacteria.

 

In short, it may be that a cellular structure is a pre-requisite for providing adequate concentrations of pre-biotic chemicals to allow auto-catalytic metabolisms to emerge.

 

[Note: I've lifted these comments (middle two paragraphs) from a working document of mine on the Drake equation. I think they are my own words paraphrasing the original articles, but they might be condensations from popular accounts at the time.]

 

I've read another slightly less complex version of this idea that says that cell like structures form when waves like the surf break on shore and oil and water forms microscopic droplets very similar to the droplets in vinegar and oil salad dressing. They are composed of two layers and contain cell sized bubbles of water and what ever other chemicals was contained in the water. You idea is a bit more detailed and allows for more complexity. I still question how the cell wall that allows in certain chemicals and lets out certain chemicals at the same time could have formed by accident. Of course when you are talking about literally thousands of billions of such "cells" forming and possibly joining all the time it becomes far more likely.

[Eclogite]

I still question how the cell wall that allows in certain chemicals and lets out certain chemicals at the same time could have formed by accident. Of course when you are talking about literally thousands of billions of such "cells" forming and possibly joining all the time it becomes far more likely.

I think this is the central point that the researchers were making. The proto cell wall is very general in the way it inhibits or admits the passage of material into, or out of the droplet. A chance combination of molecules within that wall may lead to a more useful concentration of chemicals within the droplet. If an autocatalytic reaction involving proto-cell wall molecules and components within the droplet gets underway you could have 'replicating' simple metabolisms.

 

I don't believe this is the way life began, but I believe it may have been part of the sequence.

[Moontanman]

I think this is the central point that the researchers were making. The proto cell wall is very general in the way it inhibits or admits the passage of material into, or out of the droplet. A chance combination of molecules within that wall may lead to a more useful concentration of chemicals within the droplet. If an autocatalytic reaction involving proto-cell wall molecules and components within the droplet gets underway you could have 'replicating' simple metabolisms.

 

I don't believe this is the way life began, but I believe it may have been part of the sequence.

 

I think it might have been several different functioning but separate metabolisms that came together in proto cells. these proto cells could combine and even divide due to physical processes and eventually enough of these cells were formed that could function as life, possibly with the help of free floating RNA. At each step of combining separate cells with functioning metabolisms better and better cells were formed. there is probably no one time and place where you could point and say, there is a living cell but once the cell got started they would pretty much take over possibly only leaving RNA viruses as the remnants of the time when metabolisms were separated from each other in proto cells.

[mynah]

Update on the "cells" in red rain

 

They are obviously not cells as we know them, but they do have some pretty weird qualities. I haven't seen any details about their actual composition, however.