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Old December 14 2013, 06:00 PM   #16
rhubarbodendron
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Re: Potential Habitable Planets

Into Darkness wrote: View Post
Would knockin Vesta out of it's orbit and slamming it into Venus cause enough of an explosion to eject the carbon dioxide from the atmosphere and into space to reverse the greenhouse effect?
no. You forget about mass attraction. The gas would be gradually pulled back by the planet's gravity. Also, atmospheres tend to cling very tightly to their planets. Shaking them off with just an impact is next to impossible. The best example is our own planet: about the same mass as Venus, major collision with the moon (which is a good deal bigger than Vesta) and yet we still have an atmosphere. What little of it the moon took away after the collision has long since been pulled back to Earth (though the last moon mission reported that they thought they had seen a slight haze over the moon's horizon. Personally I think it was just the dust they had kicked up themselves during their mission, maybe even at their landing. It takes a few days to settle up there.).

Venus would still be uninhabitable even if it were in our orbit and have our atmosphere: it has only an extremely weak magnetic field to ward of the solar wind. The radiation levels would be too high for Terran DNA to stay intact. It'd crumble like dust. You'd have to find some way of biological coding that is less vulnerable.
There have been suggestions of proteins in the atmosphere but a protein doesn't necessarily mean life (example: the existence of clay doesn't mean there'll be brick buildings). You can induce their spontaneous formation in the lab quite easily (the proteins', I mean, not the brick buildings' )


(edited twice for spelling - If you find another typo please simply endure it - I have a huge cold and am only half awake)
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Old December 14 2013, 08:38 PM   #17
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Re: Potential Habitable Planets

The more you think or look at it, the Earth is not only lucky to be in the habitable zone but also lucky to have it's magnetic field. In fact, it's lucky to have so much water and the gravity to hold on to an atmosphere.

I'm starting to believe maybe the Earth is rarer than many people believe and there aren't so many habitable worlds out there afterall.
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Old December 15 2013, 12:36 AM   #18
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Re: Potential Habitable Planets

Frankincense + Myrrh wrote: View Post
There was a novel about Ensign Flandry (Agent of the Terran Empire) I read years ago, iirc one world had such a thick atmosphere (which was fine for the natives) that Humans could only live comfortably on the tops of tall mountains.

Which I found interesting.

Maxwell Montes on Venus is 11 km tall and a human could survive the pressure there (about 43 atmospheres), but the temperature is still going to be over 600 F. That mountain range is about 500 km on a side, so instead of focusing on getting the entirety of Venus barely habitable, aiming at getting the mountain top habitable would make terroforming a bit easier.
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Old December 15 2013, 09:48 PM   #19
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Re: Potential Habitable Planets

Into Darkness wrote: View Post
The more you think or look at it, the Earth is not only lucky to be in the habitable zone but also lucky to have it's magnetic field. In fact, it's lucky to have so much water and the gravity to hold on to an atmosphere.

I'm starting to believe maybe the Earth is rarer than many people believe and there aren't so many habitable worlds out there afterall.
Then again, the definition of "habitable" depends on what kind of life we're talking about.

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Old December 16 2013, 01:34 AM   #20
rhubarbodendron
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Re: Potential Habitable Planets

Into Darkness wrote: View Post
The more you think or look at it, the Earth is not only lucky to be in the habitable zone but also lucky to have it's magnetic field. In fact, it's lucky to have so much water and the gravity to hold on to an atmosphere.

I'm starting to believe maybe the Earth is rarer than many people believe and there aren't so many habitable worlds out there afterall.
I'm with Scotpens there. I should think on other planets life develops in a different way. Therefore there should be a lot of inhabitable planets, only they wouldn't necessarily be inhabitable for us.
I mean our planet is perfect for carbon-based organisms with a high water ratio. But it's only perfect for us because we developed here. On other planets the organisms might be silicone based or nebula-like. They would have developed in a way that is perfect for their respective environment.

Like Dawin said: those who fit best survive. The others will get extinct.
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Old December 16 2013, 08:38 AM   #21
Edit_XYZ
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Re: Potential Habitable Planets

Rhubarbodendron wrote: View Post
Into Darkness wrote: View Post
The more you think or look at it, the Earth is not only lucky to be in the habitable zone but also lucky to have it's magnetic field. In fact, it's lucky to have so much water and the gravity to hold on to an atmosphere.

I'm starting to believe maybe the Earth is rarer than many people believe and there aren't so many habitable worlds out there afterall.
I'm with Scotpens there. I should think on other planets life develops in a different way. Therefore there should be a lot of inhabitable planets, only they wouldn't necessarily be inhabitable for us.
I mean our planet is perfect for carbon-based organisms with a high water ratio. But it's only perfect for us because we developed here. On other planets the organisms might be silicone based or nebula-like. They would have developed in a way that is perfect for their respective environment.

Like Dawin said: those who fit best survive. The others will get extinct.
There's a problem with this conjecture: Carbon chemistry has advantages silicon, etc lacks:
http://en.wikipedia.org/wiki/Hypothe...n_biochemistry
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Old December 16 2013, 12:57 PM   #22
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Re: Potential Habitable Planets

No Sanity Clause wrote: View Post
Then again, the definition of "habitable" depends on what kind of life we're talking about.
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now. Life in general, at least any more advanced form of life such as animal or human seems to require heat, light, water, oxygen and protection from space radiation. There are so many factors that add up together to allow advanced life that Earth has to be very very rare.
It's possible some form of life evolved on planets less fortunate than Earth where it's not as "paradisaical" but those worlds would still require a bare minimum of factors such as not too hot and not too cold, a protective magnetic field.
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Old December 16 2013, 06:31 PM   #23
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Re: Potential Habitable Planets

Into Darkness wrote: View Post
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now.
With zero examples of extraterrestrial life of any kind, there's no reason whatsoever to agree with this assertion.
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Old December 16 2013, 10:02 PM   #24
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Re: Potential Habitable Planets

Coach Comet wrote: View Post
Into Darkness wrote: View Post
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now.
With zero examples of extraterrestrial life of any kind, there's no reason whatsoever to agree with this assertion.
This solar system has 8 main planets, several dwarf planets and a multitude of moons, some have atmospheres, some have decent gravity levels, some have water . Not one of them other than Earth has life on them let alone advanced forms of life, which goes to show that environments not like Earths are not suitable environments for life.
Our solar system alone is statistical proof that life doesn't and cannot just spring up in any old kind of environment, a multitude of specific factors are required and such factors combined together must surely be rare.
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Old December 17 2013, 12:53 AM   #25
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Re: Potential Habitable Planets

Coach Comet wrote: View Post
Into Darkness wrote: View Post
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now.
With zero examples of extraterrestrial life of any kind, there's no reason whatsoever to agree with this assertion.
Or to disagree with it. Making assumptions about what you do not have scientific data on is bad for both sides. I think what we know, which isn't as much as we'd like to think, that since the evidence of other planets around other stars is proven, we can safely speculate that life does exist elsewhere other than earth just given the sheer billions upon billions and billions of stars in the universe.

But it may be so rare that we might not find it at all unless we somehow avoid extinction and learn the secrets of FTL travel.
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Old December 17 2013, 07:23 AM   #26
CorporalCaptain
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Re: Potential Habitable Planets

Spider wrote: View Post
Coach Comet wrote: View Post
Into Darkness wrote: View Post
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now.
With zero examples of extraterrestrial life of any kind, there's no reason whatsoever to agree with this assertion.
Or to disagree with it.
On the contrary, there are excellent reasons to disagree with Into Darkness's assertion.

Evidently, the point of his assertion is to argue that not yet having observed non-carbon-based life is a reason to suppose that it is harder for it to evolve than it is for carbon-based life. That's simply absurd, because, if it were valid, then we could apply a similar argument to conclude that extraterrestrial life of any kind is a rare thing. Based on the evidence, or rather the lack thereof, that's a totally bogus conclusion, because we simply have not ascertained how many stars in the galaxy have planets or moons with life on them. Our ability to observe the universe around us still doesn't let us do that. We don't even yet have reliable estimates. Since we are presently incapable of determining how much extraterrestrial life there is of any kind, we are incapable of determining how much of it is non-carbon-based, based on whether we directly see it.

That doesn't mean that there isn't reason to expect more carbon-based life than non-carbon-based life. I agree that there are a lot of good reasons to doubt that non-carbon-based life is easy to evolve, even assuming it's possible, however our failure so far to observe any isn't one of them.

Making assumptions about what you do not have scientific data on is bad for both sides. I think what we know, which isn't as much as we'd like to think, that since the evidence of other planets around other stars is proven, we can safely speculate that life does exist elsewhere other than earth just given the sheer billions upon billions and billions of stars in the universe.

But it may be so rare that we might not find it at all unless we somehow avoid extinction and learn the secrets of FTL travel.
Well, yeah, but what I'm saying is that Into Darkness's assertion isn't really a neutral assertion. In grossly overestimating the significance of our observations to date, it's really biased to the point of being fundamentally flawed.

Into Darkness wrote: View Post
Coach Comet wrote: View Post
Into Darkness wrote: View Post
If it was easy for life to evolve that wasn't carbon based we'd surely have seen it by now.
With zero examples of extraterrestrial life of any kind, there's no reason whatsoever to agree with this assertion.
This solar system has 8 main planets, several dwarf planets and a multitude of moons, some have atmospheres, some have decent gravity levels, some have water . Not one of them other than Earth has life
I'm just going to stop you right there, and refer you to this page.

on them let alone advanced forms of life, which goes to show that environments not like Earths are not suitable environments for life.
Our solar system alone is statistical proof that life doesn't and cannot just spring up in any old kind of environment,
No. There's still a lot we don't know about our solar system, including whether life arose on any other body in it besides Earth sometime in the past and then went extinct.
a multitude of specific factors are required and such factors combined together must surely be rare.
Well, we really don't know that yet, which is why we continue to look for things like planets around other stars and learn all we can about them, and it's also why we continue to theorize about how evolution works, how life began on Earth, and what other forms of life might exist.
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Old December 17 2013, 06:31 PM   #27
rhubarbodendron
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Re: Potential Habitable Planets

Also, there's the question: would we recognize extraterrestrial life as such if we encountered it? It might be very very different from what we know. Sometimes it's already quite difficult to spot certain lifeforms on our own planet:
Would you recognize this as a butterfly or find the locust?


and how about these?

(solution: red algae (Hildenbrandia spec.) and flagellate algae (Ceratium hirudinella))

Edit_XYZ wrote: View Post
There's a problem with this conjecture: Carbon chemistry has advantages silicon, etc lacks:
http://en.wikipedia.org/wiki/Hypothe...n_biochemistry
These advantages or disadvantages depend on the point of view. They apply only if you judge by our standards (i.e. the p.o.v. of a carbon-based organism in a watery environment). Life forms based on other elements might perhaps not share our own definitions of life and of advantages nd they might have a totally different way to store genetical information (or have no genes at all but something different).
It's a cool link, though, and they do make a lot of excellent poins there! Thank you for sharing! It's not available in my language and I would never have found it.
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Old December 18 2013, 12:30 AM   #28
scotpens
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Re: Potential Habitable Planets

Edit_XYZ wrote: View Post
. . .Carbon chemistry has advantages silicon, etc lacks:
Hey, I resemble that remark!

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Old December 18 2013, 01:14 PM   #29
Edit_XYZ
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Re: Potential Habitable Planets

Spirit of Christmas Present wrote: View Post
Edit_XYZ wrote: View Post
There's a problem with this conjecture: Carbon chemistry has advantages silicon, etc lacks:
http://en.wikipedia.org/wiki/Hypothe...n_biochemistry
These advantages or disadvantages depend on the point of view. They apply only if you judge by our standards (i.e. the p.o.v. of a carbon-based organism in a watery environment). Life forms based on other elements might perhaps not share our own definitions of life and of advantages nd they might have a totally different way to store genetical information (or have no genes at all but something different).
It's a cool link, though, and they do make a lot of excellent poins there! Thank you for sharing! It's not available in my language and I would never have found it.
About the link, you're welcome.

About my assumptions ("standards", as you post-modernistically try to put it):
It's mainly one assumption - that life is informationally highly complex, and, in order to exist, atoms (or equivalents) that can combine in highly complex, stable molecules are needed. Carbon and water are very good at making complex molecules, while having almost none of the disadvantages other proposed chemistries have.

Did you know that like is the most informationally complex phenomenon in the universe? That the universe has a single set of laws of physics - and chemistry?

A secondary assumption is that life needs energy (as in, low temperatures mean a VERY slow evolution, etc)
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Old December 18 2013, 05:04 PM   #30
rhubarbodendron
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Re: Potential Habitable Planets

I beg to differ. Life needs as you correctly say energy. But that energy needn't necessarily come from warmth. Quite a lot of organisms on our own planet live and propagate in zones that are far below freezing point. The glacier flea, to name only one. Krill lives and thrives in waters that are colder than 0°C and there is such a lot of it that several species of whales, the biggest recent animals, feed exclusively on it (and quite a lot of other animals too). And a surprising number of algae lives on snow and on glaciers, including those in the Arctic.

I very much agree about chemistry being the same everywhere (though it would appear by some experiments made on the ISS that certain reactions change their mechanisms - and their outcome - with a lack of gravity). You certainly are right about carbon being the most reactive element of the given options. Yet, even on our own planet there are organisms with a silicate skeleton, such as all Bacillariophycea, many Rotatoria, Dinoflagellata and most sponges. And even many higher plants have silicate crystals in their cells (Clivias, for example).
You will notice that all the life forms with silicate skeletons are planctic and very small. So very obviousely there are limitations to the use of silicium-complexes in organisms. Yet it's not completely unheard of.
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