[ukmicky (OP)]

Could there be life on other planets.

If you go by earths example then shouldnt the anwser be,unlikely.

The earth has been around for about 5 billion years, and yet life has only started here once, as all life on earth is related.

once in 5 billion years would mean life must be so hard to start in the first instance that maybe life on earth is just a fluke[]

There are also many other factors that have got be taken into account which has aided life and complex life on our planet to survive.

Like our position in our galaxy,our type and size of our sun and the fact that its not a binary. Jupiter handy for removing the odd comet that comes our way. the moon. the tilt of our planet very handy that. the size of our planet and its position in our solar system ,it's molten core , magnetisphere. oxygen nitrogen mix. the list could go on for ever.

May be our planet is unique and the life on it is unique. is it so unlikley that we are alone,could we be the first.[]

Michael                                     

[neilep]

I have no doubt whatsoever that there IS life elsewhere.

Yes, the circumstances required for life are not condusive to a mass outbreak where ever we look in the Cosmos but when you consider that our Sun is one of three-five hundred billion suns in our galaxy, and our galaxy is one of three-five hundred billion galaxys (give or take a few billion !)...and it has been shown that there are indeed many many many planets out there, far more than we ever could imagine.....the chances that this planet is the only planet that supports life is not even worth considering.

And life can take many types and forms. Just dive in the ocean and keep going down and you'll find life that doesn't require light and oxygen to exist, check out the deepest dankest caves and pools, play around in the hottest springs and you'll find algae and stuff, just check the back of your fridge, I'm sure there is life there that is developing it's own intelligence !!!

Life as we know it is only contained to our planet, life is out there , it has to be, the friggin Universe is just too friggin large and the maths make it so !!..and who knows what other ' types' of life exist !


It is even suggested that life on this planet hitched a lift in/on a meteor that crashed landed here.



STAR TREK QUIZ:

I have used two well know Star Trek Phrases above, what are they ?

Prizes will be determined by the gender of the quiz winner !

Men are the same as women.... just inside out !!

[johndiver]

UK: Your concern is real but your logic is flawed.
Life is simply the result of complex chemistry. Molecules such as DNA control chemical reactions which consume surrounding molecules and use their pieces to make copies of itself. Whenever we have a liquid solvent (water, ammonia, methane), carbon-based molecules, and a substrate (silicon-based clay) there exists a possibility that one or more molecules will form that have the properties of encoding information, cutting apart other molecules, attaching smaller molecules into strings of carbon, utilizing energy from sunlight or chemical reaction, and repairing the information carrying molecule. Once this system forms and is able to withstand environmental stresses, then the base of life has begun. Whether it evolves into sapient beings or beautiful flowers is another matter.
The other big theory out there (pun intended) is Panspermia. Astronomers have discovered organic molecules floating in interstellar space and have raised the possibility that comets have picked up these molecules and crashed into earth and other planets with these precursors of life. If so, then comets may be spreading the seeds of life around the galaxy, where they can replicate and evolve as conditions permit.
If you'd like to learn more, I strongly suggest reading the Gaia hypothesis by James Lovelock. Also use the search terms "carbon chauvinism" if you'd like a real interesting look at how carbon became the molecule of life.

[ukmicky (OP)]

Thank you all for your comments.

It is a horrible thought that we could be alone; I personally prefer to believe that the universe is teeming with life.
However I’m one of these people that has to always question everything in order to learn and then believe what’s generally accepted. Is it a good or bad thing, I don’t know really, but I do know it tends to piss off many people.[]
                      --------------------------------------------------------------------------


The building blocks for life may have come here from space or they could have been created on the earth through electrical storms
However it is still a fact that every living thing on earth is related, we all come from one single common ancestor. Whether you’re talking about plant life or animal.We share sixty percent of our DNA with the humble banana [Neil your related to a banana][] or the tree that produced it.[]
And unless the double helix and a large percentage of its DNA structure is a universal blue print for life, it must mean all life on earth emerged after one single event that created one single simple life form that somehow survived to divide and evolve into all the various living forms of life, be it animal or plant.


Which means the start of life on earth happened once, one event in the total history of the world. That’s says to me that the chances of it happening lots of time’s on lots of extraterrestrial planets that are like or unlike ours is remote.

Maybe it has happened again in a distant galaxy far far away but it must be such a rare event that it also says to me that ok we may not be alone in our universe but as far as the Milky Way is concerned we could be..

If life here on earth was created on more than one occasion then the chances are that there would be other life forms of life that didn’t share any DNA characteristics with us, possibly with other forms of DNA structures, maybe even triple helixes,
or maybe something other than DNA
Michael                                      

[johndiver]

I have read a few essays about how finely-tuned the world is for life to exist ... for example, Gravity is roughly 10^39 times weaker than electromagnetism. If gravity had been 10^33 times weaker than electromagnetism, stars would be a billion times less massive and would burn a million times faster, and no astronomers would ever come into existence to talk about this matter.
This is the sort of theorizing that makes us think about what life is from the view of quantum physics.
http://en.wikipedia.org/wiki/Carbon_chauvinism
http://en.wikipedia.org/wiki/Anthropic_principle

[ukmicky (OP)]

Once life has been created then it seems going by earth’s example, life will evolve and find a way to survive even in the most extreme of environments.

However Its not really about how finely tuned the earth is for life to survive, as life will try to make do with whatever its got and will explore the potential of any environment it happens to be presented with.

The problem is life has got to be created first and that it seems is not as easy as people seem to believe.

Meteorites have been found to contain amino acids the building blocks of life, one meteorite was found to contain over seventy different types but only six of the types that are essential for life.

Dumping all the required ingredients, the twenty or so amino acids etc required for life in a test tube is one thing,
but it happening naturally is another.

Remember, a far as we know it has only occurred on earth once
G
etting all the required ingredients together at the right time with the right conditions maybe not that easy for nature to achieve  
[]

Michael                                      

[johndiver]

Keep in mind that our planet could be considered toxic to other life forms. For example, we have free oxygen in the air and dangerous amounts of calcium in the our oceans. Not to forget, do you realize that water is able to dissolve more substances than any acid?
Either way, I like James Lovelock's observation that in order to determine the likelihood of life on another planet, simply look for the presence of atmospheric molecules that are unstable and therefore likely produced by a lifeform. That way, he argued, to look for extraterrestrial life you'd be better off investing in better telescopes than in rockets to reach Mars with sensing devices.

[another_someone]

quote:Originally posted by ukmicky

Could there be life on other planets.

If you go by earths example then shouldnt the anwser be,unlikely.

The earth has been around for about 5 billion years, and yet life has only started here once, as all life on earth is related.

once in 5 billion years would mean life must be so hard to start in the first instance that maybe life on earth is just a fluke[]

There are also many other factors that have got be taken into account which has aided life and complex life on our planet to survive.

Like our position in our galaxy,our type and size of our sun and the fact that its not a binary. Jupiter handy for removing the odd comet that comes our way. the moon. the tilt of our planet very handy that. the size of our planet and its position in our solar system ,it's molten core , magnetisphere. oxygen nitrogen mix. the list could go on for ever.

May be our planet is unique and the life on it is unique. is it so unlikley that we are alone,could we be the first.[]

Michael                                      

Would somebody tell me what they mean by 'life'?  If we are to say whether life exists elsewhere, then we should first clearly define what it is that we would define as 'life'?

If all you are looking for is reproduction, then stars themselves will, in their death throws, beget a new generation of stars.  There now appears a significant possibility that some sort of bacterial life exists on Mars.  What kind of life are you looking for when you ask about extraterrestrial life?

Beyond the question of whether there is life out there, is the question of whether life is capable to crossing the vast expanse of nothing to reach us, or that we might reach them.  If the closest planet that supports life were to be several hundred million light years away, then even if they could send out a ship to reach us, by the time that ship returned home, several hundred million years would have elapsed on their own planet, and the original purpose of their mission would seem rather irrelevant to the world they would return to.

[Ultima]

The problem here is that you are looking at SPECIALISED HIGHLY EVOLVED forms of life that have been home grown here on Earth and trying to put them into some sort of inter stella standing! Saying that life only appeared on Earth once and everything is related isn't entirely true...

How do you know there aren't new forms popping in to existence all the time but they don't have a chance because of everything else around them? It's a bit of a first come first served thing in evolution, then you have to wait for something to become extinct to take it's place.

I don't think I could easily compare an  archaebacteria extremophile living in an ocean thermal vent or deep within solid rock with a Kangaroo... they aren't even chemically that similar they use completely different processes to fuel them, and one saves people from wells, the other doesn't! People have just started to find these "giant viruses". It's not clear how many there are, how long they have been around or what there role is, or if they can be called "alive".

Looking at all those "what if this physical variable was changed life wouldnt exist" etc... How do you know??? Have you created some massive physical model and processed it for billions of billions of years to see what kind of structures emerge??? Life is just the self organising and replication of a stable pattern or structure of molecules, at least in my book! Or not even molecules... electrons in plasma's, bits of data, anything so long as it's a persistent self replicating pattern that is subject to some process of change through an environmental interaction.

http://en.wikipedia.org/wiki/Extremophile
http://en.wikipedia.org/wiki/Kangaroo

[ukmicky (OP)]

originally posted by ultima The problem here is that you are looking at SPECIALISED HIGHLY EVOLVED forms of life that have been home grown here on Earth and trying to put them into some sort of inter stella standing! Saying that life only appeared on Earth once and everything is related isn't entirely true...

How do you know there aren't new forms popping in to existence all the time but they don't have a chance because of everything else around them? It's a bit of a first come first served thing in evolution, then you have to wait for something to become extinct to take it's place.

I don't think I could easily compare an archaebacteria extremophile living in an ocean thermal vent or deep within solid rock with a Kangaroo... they aren't even chemically that similar they use completely different processes to fuel them, and one saves people from wells, the other doesn't! People have just started to find these "giant viruses". It's not clear how many there are, how long they have been around or what there role is, or if they can be called "alive".

Looking at all those "what if this physical variable was changed life wouldnt exist" etc... How do you know??? Have you created some massive physical model and processed it for billions of billions of years to see what kind of structures emerge??? Life is just the self organising and replication of a stable pattern or structure of molecules, at least in my book! Or not even molecules... electrons in plasma's, bits of data, anything so long as it's a persistent self replicating pattern that is subject to some process of change through an environmental interaction.
__________________________________________________________________________________________________________________


TO ULTIMA

Firstly let me appologise for the format of the following or any typing errors. i'm tired i need some sleep[|)]
________________________

I’m not just talking about complex life forms I’m talking about even the most basic forms of life on earth. The smallest and simplest forms of life the single celled organisms called prokaryotes which inhabit almost every place possible on earth from deep ocean vents or hot springs to the freezing poles share RNA/DNA with us.
So yes your kangaroo may not look similar to extremophiles halo bacteria living in deep ocean thermal vents but we do have a common ancestor  and in reality are related to you and me.And yes they may use different life processes but follow you family tree far enough back and you will find your ancestor which didn’t use oxygen but released it as a waste gas.  
Ok they didn’t walk around on arms and legs but we are genetically related to them.
And so as far as we know Yes every living thing on earth is related and my statement is entirely true.

It is a fact that everything, be it algae, bacteria, a plant or you and me share parts of our genetic makeup with each other, there are individual genes on the ribosomal RNA which are common to all life plant or animal and the only way that is possible, the only way is if we all share a common ancestor.

Also every living thing on earth needs the same 20 amino acids.
Every living thing has cell structures (Human cells evolved from plant cells).
We all use the same nucleotides in our genes.
We all use Adenosine triphosphate (ATP) to transfer and store energy within our cell. ATP is also used for the synthesis of nucleic acids. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses.
(Even though part of our genetic makup most likely came from virus's that integrated into there hosts DNA,viruses do not come under most people’s definition of life)  
ATP molecules are also used to store the usable energy that plants convert in cellular respiration. There are so many things which are common to all life on earth that the one and only explanation is we come from one single event which created one single life form on earth.

We only have proof that life has started  on earth once and going by that evidence means life is such a hard process to begin naturally, we could be on the only planet in our galaxy with life. its possible.
And as the rest of the universe is basically made of the same stuff as us and our planet and many of the rocks and comets floating around in space contain amino acids which are the same as whats found on earth (no new ones), it’s a good bet that any life on any other planet would share similarities and with us like be carbon based and be dependent on water.
and so any difficulties the earth has had in respect to the creation of life,any other planet would probably have the same .[]

I would love to be wrong, but i bet life isn't common in the universe and i bet it's never found on mars or anywhere else in our solar system.

Most people hate the thought that we could be alone or that life is very rare event in the universe,and unfortuanatly that possibility does exist.
Michael                                      

[Ultima]

There are 22 genetically coded for amino acids; some dude added in two extra codons for unnatural amino acids to a bacteria to produce new proteins! Plus some of these other amino acids were found very recently and weren't known to exist. So it's quite possible there is some life hanging around using some amino acid no one noticed before. I remember reading someone had found a bit of life using a random amino acid, different to everything else... I'll see if I can dig up a reference.
Because all life is made up of the same types of molecules doesn't make them the same or related. It's just means it's the most stable and efficient form to be in on the Earth.
You will have to define what you mean by "Life started once" as soon as we had biological molecules surrounded by membranes (or proteins) reproducing we had life. I imagine new forms start from the ground up more often than not, but they get consumed by something more advanced and bigger around them.
We also know that throughout history completely unique sets of organisms nothing like what we see today got killed off in the "Permian-Triassic extinction event" which wiped out about 90% of all species of life. Everything thats here today is from 10% of the types of life that used to exist. If you go further back there are more extinction events, who knows what sort of zany life existed before life formed shells to leave fossil records!
I understand what you are trying to get at, but reasoning that chemically life is similar means they must be related, does not hold up in the real world.
Life picks out the best way to do things as shown through convergent evolution of radically different species into the same niche role. It only makes sense that the same system of chemically stored information is used. I'm no chemist, but I don't think there are that many other molecules you could use to do the same job. Silicon can replace Carbon but you don't get anywhere near the same amount of molecules to use. RNA and DNA are good examples that there is more than one way to do things. One of which is more complicated and newer than the other!
It's like saying that all electronic devices are exactly the same because they use electrons, but in reality there have been several seperate reincarnations of electronics in different froms doing the same thing.

Chemistry is just the hardware, LIFE is the software that persists within the chemical framework! [] You can tell im a Computer Scientist/A.I. peep looking at Biology!

[Dr. Praetoria]

One interesting discussion I heard, was that such a life creating planet would have to have a moon that would stabilize it, permitting seasons or climates that allowed such life to form.
Doc

[another_someone]

The moon supposedly stabilises the Earth's orbit, but it also creates tides.  I do believe that there has been speculation that life started in the intertidal regions.  If this is the case, then the moon would have been required to create the tides.

Another factor where the moon may have been important may have been in the nature of its formation.  The current theories seem to indicate that the moon was created by a collision between the Earth and another body, and that this other body skimmed a fair amount of material from the surface of the Earth, but did not take material from the depths of the Earth (hence why the moon is poor in iron, and other heavy elements that form the mantle and core of the Earth).  This would indicate to me that the collision may have left the Earth with an extra thin crust, which might than have been more conducive both the volcanism (including deep sea vents), and to plate tectonics.  Another theory about the origin of life was that it originated near deep sea vents, where the energy of the vents was used to fuel early life (what does seem certain is that the earliest life was not dependent on the kind of photosynthesis that is so common today, and so would have required some other energy source).

I don't personally believe that stability is that important for the creation of life.  On the contrary, I believe life is a consequence of instability.

Certainly, the more variability there is in the environment, the more opportunity there will be for evolutionary change.  In that respect, the creation of tides is one form of local environmental variability, although the Earth has has much more significant environmental shifts over its history, and through them, it has been driven to ever more radical evolutionary changes in the life it supports, as that life must constantly adapt to the shifting environment.  The regular mass extinction events that occurred on this planet, although they were clearly toxic to the life of the time, were each a prerequisite for the next stage of evolutionary progress.

As I mentioned earlier, there is still the question of what is life?

Ukmicky has suggested that DNA/RNA is a common factor for life on earth.  I think Ultima has better identified that what is import is the patterns, the information, that is stored within DNA, rather than the DNA itself.  Probably, even more relevant than the information stored in the DNA itself, is the nature of the system that this information describes.  What we see as living organisms are enclosed bodies (cells) that contain a complex set of micro environments that operate to isolate a complex series of interconnected chemical processes.  The DNA stores the blueprint for the protected system of chemical reaction vessels that is a living cell, and it ensures that each system is an approximate replicate of its parent, but, in my view, it is the system that is important, not the blueprint.

johndiver has mentioned that the environment on this planet might be toxic to many life forms.  In my view, that actually is an important reason why life may indeed have developed on this planet.  As I said above, living cells are a system of isolated reaction vessels, and one reason that they do need to be isolated from the outside environment is precisely because the outside environment would be toxic to the internal contents of the cell.

The amino acids that seem to be so easily available in much of the universe may be a basic building block for life on this planet (and maybe on other planets), but having the building blocks is not of itself enough to construct life - there must have been environmental factors that caused those building blocks to come together in the way they did.

The other factor that no-one has mentioned is that while so much has been said about amino acids, that are used to build proteins, enzymes, and DNA; what about the lipids and sugars that are also important constituents or life?  Could early life have been formed without these?  If so, then what substitutes did early life use in their place?


http://www.cmbl.org.pl/vol9sup2/V9Suppl2Page97.pdf

quote:
The first forms of cellular life required membranes that were probably made of amphiphilic compounds such as lipids and phospholipids. Lipid membranes are crucial to the structure and function of all cells and their role in the origin and evolution of life is of considerable interest.

[ukmicky (OP)]

To another_someone

when i wrote about dna/ rna i didnt quite explain it correctly
what i mean't was that we share them instruction within the dna that you wrote about. just like we share 98.4 % of our genetic material with chimpanzees and 60% of them instructions with a bannana,(thats the weird one) we also share identical instructions with every form of life on earth, plant or amimal. and the only way we can share identical material, complex identical instructions  with every thing is if everything is related. there is nothing on earth that is not related its a proven fact.
Not one of my facts but a proven scientific fact.

Michael                                      

[another_someone]

To ukmicky:

OK, I probably was not addressing the totality of what you wrote either.

Ofcourse you are right, the fact (although I'm not sure that there is such a thing as a scientific fact, only scientific observations and scientific theories - but that is semantics) that we share so much of our DNA does mean that we must be related, but it does not show whether we are related by a single common ancestor, or by marriage.

There are many ways in which organisms exchange DNA, and the simpler the organism, the easier it appears to be to exchange DNA.  Bacteria exchange plasmids, and even higher organisms (as you pointed out) will capture viruses that will be integrated into their own DNA.  Thus, it is quite possible that several ancestors exist, and that DNA from some branches of of the tree of life (possibly now extinct) were integrated into other branches of the tree of life, and continued to survive as hybrids, these hybrids then out-competing the earlier thoroughbreds.

[Ultima]

ukmicky I agree that today most multi celled life has it's roots with many common ancestors. But I disagree that this means "life started once".

As I mentioned we have mass extinction events all the time and life starts again. Most of the genetic material we share codes things which are common to all eukaryotic cells. I haven't checked but I doubt we share a great deal with prokaryotic life...

If every living thing was wiped out through radiation today; it would bounce back rapidly after the radiation subsided! Guess what it would look fairly similar to todays life because the same compounds are kicking around. Phospholipids form a membrane to encapsulate biological reactions, and you end up with some form of cell again. Because something is similar in appearance doesn't mean it's realted.
 
For years people thought flying foxes were bats, turns out when we looked in detail at their brains, genome and lifestyle they are closely related to lemurs and other primates (including us) and not bats. This kind of convergence is caused by a similar past and moving to the most efficient form to fit a niche environment. If that kind of thing happens on a large scale. It's not a great leap of the mind to imagine that chemically a similar process might take place. Granted this is pure speculation but it's near impossible to prove or disprove thanks to not being able to speed time up or accurately relate historical species 100% correctly.

[another_someone]

To: Ultima,

The major hole that I can see in your argument is not that it is impossible, simply that within that part of history that we can see in the fossil records, that is not what happened.

We have had many mass extinction events, but at no time have we ever had all life wiped out, it has only ever been a case of wiping out most of the life on the planet.  What would happen if all life were wiped out is speculation.

[ukmicky (OP)]

To another_someone

you got there before me with your above post. as for the other points raised i will post a reply.  but i need to check out something out first.




Michael                                      

[Ultima]

Yeah I did mention it was pure speculation []
I think the main thing is you guys are thinking "whole new life" as in it's nothing like what is around now. I have very strong doubts that chemically anything else would arise on Earth for the pure fact that it's allready how it is. Unless some magical molecule from outer space plants some new form of life thats better suited than the current chemical systems it's just not going to happen. When I say life starts again, those 10% survivors are only going to be from a narrow band of specialisation and will evolve to form organisms that resemble closely what was there before. This includes resembling the same chemistry. If you are going to live in a harsh place on Earth certain things are going to be required.

The main thing that got me going is that Michael said we share 60% of our genes with a bananna. My questions is this. How many genes does a bananna have in it's genome compared with a human? It's like saying someone who has AIDS shares 100% of their genetics with HIV!!! It's ok to make the comparison with a chimpanzee because we are clearly related to them directly. We can see the history of common ancestors. You get all sorts of statistics saying how much we share with a fly or a cabbage etc. These are worthless; because we share the same codons for a protein that is vital for the survival of all eukaryotic cells doesn't mean we are related in anyway!

You get a lot of the chemistry of a cell for free such as the formation of a membrane, without any sort of genetics coming in to the picture. I can't believe that all known life would come from a single original self contained chemical reaction. I bet there were loads that worked in almost exactly the same way chemically with just a few differences between them. But regardless of how similar chemically they were they are unique and unrelated. The fact they all ended up forming something that looks remarkably similar is probably from crossover between them early in history and the addition of some form of genetics that allows them to converge on an efficient form that works. We still get this process happening now when single celled organisms divide and capture bits of the surrounding environment inside themselves or get infected by a virus and incorporate its genetics and proteins.
Michael you still haven't defined what you mean... In your eyes what would have to be visible to prove life started out from more than one source on the Earth? Some organism with radically different chemistry? Like say silicon instead of carbon based? What?

[Ultima]

I have a question that might clear things up. I consider Viruses, Prions and Viroids in some form to be "alive" although they can't do everything themselves they are a persistent replicating form, they act on a different scale to cells persisting more through chemical reaction than active involvement with the environment around them.

Do you consider them a form of life?

If so thats instantly one form of life that is very different from a cell. A Prion isn't even genetic! It certainly wouldn't have evolved from a cell or vice-versa. I know any biologist wouldn't agree with me, but hey I can be as deluded as I like []