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Suggestion for very young planets with life
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| smjjames | Date: Thursday, 13.09.2012, 16:30 | Message # 1 |
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World Builder
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| Just an idea here, I've seen some terras with life on it that are a few hundred million years old (haven't seen any that are less than 100 million years old) and often look lush with life. The only problem is that these are often way too young for life to even have moved onto land. Those that are 700, 800 million years old, maybe, since life would have had some time to actually evolve, but 100 million years is too early for life forms to get onto land and evolve photosynthesis.
I'm not saying that there shouldn't be worlds that young with life, just that said life wouldn't really have colonized the land that early, unless of course the planet has been terraformed by aliens.
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| CyberItalian | Date: Friday, 14.09.2012, 13:18 | Message # 2 |
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Astronaut
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| well, you are calling in some complicate thinking.
Just because OUR planet's life evolved in the bilion of years, this doesn't mean that ALL life forms MUST have a evolution that spans throught the billion years.
Just think about it:
We're carbon based, but there are a LOT of many other chemicals in the universe.
Nitrogen, oxigen, hydrogen, sodium, uranium, cesium, iron, copper, gold, lead, or any other chemical element can and most probably WILL be the chemical base for life forms.
Who knows, our chemistry is limited to what we can do here on this planet and in this solar system, maybe in another solar system, with more UV rays, or more X-ray, or whatever, chemical reactions for some elements might be accelerated.
There might even be silicon-based life somewhere (no, not computers, real life forms) in the universe.
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| HarbingerDawn | Date: Friday, 14.09.2012, 13:54 | Message # 3 |
 Cosmic Curator
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| Hello CyberItalian, and welcome to the forum. Please take a moment to read the forum rules.
Quote (CyberItalian) Nitrogen, oxigen, hydrogen, sodium, uranium, cesium, iron, copper, gold, lead, or any other chemical element can and most probably WILL be the chemical base for life forms.
How so? Many of those elements are not suitable for making the kinds of chemical bonds necessary to form the basis of biochemistry. Carbon is very versatile and capable of forming the basis for wonderfully complex molecules with ease. Silicon has similar properties and so could also serve a similar purpose on another world, but that would probably be a very rare case. How could nitrogen form the base for any kind of life? Nitrogen generally doesn't react with anything, that's why our air can be made mostly of it without affecting us in any way. All of the other elements you mentioned have problems of their own. Not any element can form the basis for biochemistry.
Quote (CyberItalian) Just because OUR planet's life evolved in the bilion of years, this doesn't mean that ALL life forms MUST have a evolution that spans throught the billion years.
But it is likely in most cases. There are certain things that have to happen in order for complex life to emerge, and the processes that drive these things are extremely slow. The process of evolution and natural selection working on simple self-replicating molecules is an agonizingly slow one. Even if those molecules eventually somehow get incorporated into some other structure to form a prokaryotic cell, it is still a very slow process. It can't speed up until the advent of sexual reproduction, which would probably require eukaryotic-type life. Such life took over a billion years to evolve on Earth, and since sexual reproduction took over a billion years more, there is no reason to think that it would take any less than several hundred million years on some other world. And even if it did, that only sets the stage for the further development of life. You still need photosynthetic plants capable of living on the land to emerge, or some other chemical process to be used in lieu of photosynthesis.
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Edited by HarbingerDawn - Friday, 14.09.2012, 14:23 |
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| apenpaap | Date: Friday, 14.09.2012, 14:18 | Message # 4 |
 World Builder
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| Quote (CyberItalian) We're carbon based, but there are a LOT of many other chemicals in the universe.
Nitrogen, oxigen, hydrogen, sodium, uranium, cesium, iron, copper, gold, lead, or any other chemical element can and most probably WILL be the chemical base for life forms.
Actually, of those, Nitrogen is the only one that even forms enough bonds to make complex molecules. Oxygen only forms two bonds, so while you could make atomic chains with it, that's all. Hydrogen only forms one bond, so is even less suitable. The others are all metals, which mainly tend to play nano-scale communism and form big complexes of shared extra electrons. They don't form molecules at all, and the only ways they can be in them is if non-metals formed charged molecules and they're attracted by them. Most of those are also far too rare for a biosphere to be based on, since they only form in supernovae.
Nitrogen could theoretically be the basis of complex organic molecules the way carbon does, since it forms three bonds, but in practice there are some big difficulties with that. It tends to form N2, for one, which is as good as inert. It's also a lot rarer than carbon and oxygen due to being an odd-numbered element while those two are even-numbered (stars mainly make even-numbered elements because most of their nuclear fusion prcesses beyond helium involve a helium-nucleus being added to another nucleus).
Quote There might even be silicon-based life somewhere (no, not computers, real life forms) in the universe.
That's more probable than any of the others, but there are some problems in comparing silicon to carbon: for one, it has some metallic properties that might make organic chemistry trickier. Another problem is it doesn't like to form the chains carbon forms, unless there's an oxygen atom between each silicon atom, making it more complicated. Perhaps the biggest problem is that while burnt carbon forms CO2, which can still be used organically, burnt silicon forms SiO2, also known as sand, which really doesn't do that much any more. It's also a solid, not a gas, which makes its redistribution a lot trickier. The very fact that life on Earth is carbon-based, even though there's FAR more silicon (the thrid most abundant element on Earth, shortly after iron and oxygen, while carbon is on twelfth place, a hundred times less abundant) tells us that it is probably much less likely for silicon-based life to form. I don't consider it impossible, though.
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Edited by apenpaap - Friday, 14.09.2012, 14:19 |
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| CyberItalian | Date: Friday, 14.09.2012, 14:19 | Message # 5 |
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Astronaut
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| Thanks for the welcome.
Quote (HarbingerDawn) How so? Many of those elements are not suitable for making the kinds of chemical bonds necessary to form the basis of biochemistry.
Well, mine was more a theory, but that's true, most of the elemnts i mentioned aren't much adapt to life.
But still, the universe's so big that maybe there DO are life forms based on a whole different chemistry or even physics (again, it's just theory, and we're getting into the off-topic :P).
Quote (HarbingerDawn) But it is likely in most cases. There are certain things that have to happen in order for complex life to emerge, and the processes that drive these things are extremely slow. The process of evolution and natural selection working on simple self-replicating molecules is an agonizingly slow one. Even if those molecules eventually somehow get incorporated into some other structure to form a prokaryotic cell, it is still a very slow process. It can't speed up until the advent of sexual reproduction, which would probably require eukaryotic-type life. Such life took over a billion years to evolve on Earth, and since sexual reproduction took over a billion years more, there is no reason to think that it would take any less than several hundred million years on some other world. And even if it did, that only sets the stage for the further development of life. You still need photosynthetic plants capable of living on the land to emerge, or some other chemical process to be used in lieu of photosynthesis.
Again, it's just a theory, but think about it.
Some bacteria reproduce very fast, maybe in other worlds the bacteria evolved rapidly enough to become complex life.
Also, sexual reproduction ain't the only mean throught which life can reproduce, althought this is praticly the only meaning of reproduction we can recognize in the complex life forms as we know them.
Returning to OP: the question is legit.
It's like if there was a white dwarf or a neutron star about 8 billion years old.
That'd mean that the star from which it originated lasted pretty much 5-6 billion years, and wouldn't it have been dying a bit too fast?
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| HarbingerDawn | Date: Friday, 14.09.2012, 14:30 | Message # 6 |
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Cosmic Curator
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| Quote (CyberItalian) even physics
The laws of physics are the same everywhere. There are some things that will just not work. If there are very different kinds of life than what we've discussed, then they will probably be so different that we might not recognize them as alive. But otherwise, they are likely to have a kind of chemistry roughly analogous to ours.
Quote (CyberItalian) Also, sexual reproduction ain't the only mean throught which life can reproduce
I know, but it is required for natural selection to begin moving rapidly and accelerate the process of evolution. Fully asexual reproduction allows effectively only one avenue for introducing changes between generations, which is random mutation. This is a very slow and inefficient process. Hence, sexual reproduction or something similar needs to occur for evolution to accelerate enough to produce varied and complex life forms in a short time.
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| CyberItalian | Date: Friday, 14.09.2012, 14:33 | Message # 7 |
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| Again, it's just theory.
I think it's gotten clear in about just 3 posts that i go for theory and thinking a bit too much. xD
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| smjjames | Date: Friday, 14.09.2012, 15:23 | Message # 8 |
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World Builder
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| Quote (CyberItalian) We're carbon based, but there are a LOT of many other chemicals in the universe.
Nitrogen, oxigen, hydrogen, sodium, uranium, cesium, iron, copper, gold, lead, or any other chemical element can and most probably WILL be the chemical base for life forms.
Uranium? Seriously? Cesium reacts VIOLENTLY with water. I'm With Apenpaap though in that of those, only nitrogen would really work, but even then, it's not as good as carbon is. Most of those listed are definetly used BY life though, however I'm not aware of any protiens that use gold (which is famous for resistance to oxidation), uranium (radioactive), lead (toxic), or cesium.
Quote (CyberItalian) Returning to OP: the question is legit.
It's like if there was a white dwarf or a neutron star about 8 billion years old.
That'd mean that the star from which it originated lasted pretty much 5-6 billion years, and wouldn't it have been dying a bit too fast?
Uh, the massive stars that form neutron stars/pulsars don't live very long, in fact the youngest neutron star/pulsar known is 330 years old http://www.nature.com/news/2011/110201/full/news.2011.64.html Similar for white dwarfs as the youngest known is 500-600 million years old http://en.wikipedia.org/wiki/G29-38 . In fact, how old would a white dwarf or neutron star be from a supernova or nova that happened just now (in some distant galaxy or some other part of this galaxy? 
Back to the topic:
I'm not disputing that life may have gotten started as early as 100 million years after the planet cooled and oceans formed, never did. What I'm trying to say is that if life had JUST gotten started, it wouldn't have gotten onto land just yet. In fact, it probably couldn't happen until there was enough oxygen in the atmosphere (unless there was some other composition or a thicker atmosphere that stopped more UV rays) to keep UV rays from the sun from frying any bacteria that tried to coloniize the land. http://www.sciencedaily.com/releases/2011/10/111019181210.htm
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