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Earth May Harbor a Shadow Biosphere of Alien Life
An anonymous reader sends us to Cosmos Magazine for a speculative article arguing that a 'shadow biosphere' may exist on Earth, unrelated to life as we know it. If such non-carbon-based life were found here at home, it would alter the odds for how common life is elsewhere in the universe, astrobiologists say. "The tools and experiments researchers use to look for new forms of life — such as those on missions to Mars — would not detect biochemistries different from our own, making it easy for scientists to miss alien life, even if [it] was under their noses. ... Scientists are looking in places where life isn't expected — for example, in areas of extreme heat, cold, salt, radiation, dryness, or contaminated streams and rivers. [One researcher] is particularly interested in places that are heavily contaminated with arsenic, which, he suggests, might support forms of life that use arsenic the way life as we know it uses phosphorus."
It's life, Jim. But not as we know it.
Or the researcher is secretly needing arsenic to do his more brilliant colleague in the old Victorian-era way, having learnt from too many Agatha Christie novels.
...may exist on Earth but we won't be able to look for it until we define it.
Sounds pretty clear to me. Maybe rocks are intelligent. How would we know? Has anybody thought to ask?
http://michaelsmith.id.au
Interesting theory, but I seem to remember my biology teacher discussing silicon-based life, and how it was much less likely to develop as carbon atoms produced much more stable molecules, especially on planets like Earth with water and nitrogen/oxygen atmospheres. Carbon-based life just "works" better on Earth.
On planets with radcially different environments there's probably a lot of potential for life that's totally different from ours, but I think it's fairly unlikely for us to discover it here.
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Not an expert in biology, but unless these contaminated areas have been contaminated for a very long time (read tens of thousands of years), and are quite large, the chances for life to have sprung up seem very, very slim. Current life needed millions of years to gain a firm foothold and start building up complexity. Lucky meteorites aside, starting from zero is bound to be hard.
If the experiment succeeds (here or elsewhere), and something "life-ish" is found, the results will still be tricky to classify. Can a given chemistry lead to increasing complexity, or is it just a dead end? Without hindsight, this seems like a very difficult question.
Or Red Dwarf, "The End".
Captain Hollister: Just one thing before the disco. Holly tells me that he has sensed a non-human life form aboard.
Lister: Sir, it's Rimmer
this is how life as we know it uses phosphorus
some of these arguments often sound plausible until you examine the mechanics for life. water for instance, has unique properties not shared by any other compound - the ability to be neutral, liquid at reasonable temps and be able to transport other elements. the same goes for carbon. nothing else is going to be able to put together a tangible life form.
If you mod me down, I will become more powerful than you can imagine....
http://www.newscientist.com/article/mg19826533.600-early-life-could-have-relied-on-arsenic-dna.html tried looking up some examples of non carbon based life on earth that I'd heard of but couldn't find any however the ecology of undersea volcanic vents pretty much threw most ideas about heat tolerance and toxins being a problem out of the window.
Build a Man a Fire, and He'll Be Warm for a Day. Set a Man on Fire, and He'll Be Warm for the Rest of His Life.
Oh yeah...
You can't swap silicon for carbon in DNA. Silicon doesn't have the same talent for directionally bonding to itself. You can get get multiple bonds if you stick an oxygen in between, but the oxygen always has electron pairs that make it open to attack. There is no equivalent of the stable and inert paraffin chain.
If you were to have silicon-based life, then it would probably not use chain molecules. Suppose you had a planar silicate structure that catalysed the formation of a similar layer on top of it. The layers might then separate or exfoliate and then catalyse other copies of themselves. Some formations would be more stable, or would come out of solution at lower concentrations, and thereby 'predating' on less successful conformations by lowering the conentration of valuable components, and causing the other to go back into solution.
This is pretty dull sort of life - it isn't really much more than crystallization. No antennae, no ray-guns, no 'greetings earthlings, we come in peace'. However, carbon-based life was probably a pretty dull affair before the cell wall. It would have relied on random variations in ambient chemistry and temperature to do anything, and a lot of time must have been spent waiting for the right conditions for the next move. The simpler viruses are more like big chemicals than small creatures.
I remember a Scientific American article from about 1983 where it was argued that some of the lamellar structures that you can get in pre-cambrian clays may have been just such a system. No easy way of telling now, of course, because carbon based life would probably have killed it off. If it could be said to have been alive in the first place.
"They're made of meat."
"Meat?"
http://home.earthlink.net/~paulrack/id82.html
dark basements below older human habitation? im sure theyll find a new asexual species resembling man...
I am very sucseptible to "let's have another drink"
I didn't find it on Google, but about 30 years ago I read an account of a creature like a giant sand dollar that was dislodged from the deep ocean by an undersea earthquake. I can't verify it until I find a reference, but I recall that the scientist examining it found that it was largely silicon, hydrogen, and sulphur (and decayed rapidly giving off H2S). His theory was that it was silicon based life - and that its chemistry required deep ocean temperature and pressure to remain stable. (Note that there are carbon based ocean creatures able to process silicon to create SiO2 structures.)
"Alien" means "not from here." If our planet harbors a resident life form which we're not aware of, that doesn't make them alien. It just makes us ignorant.
It's not a lie. It's the truth with lossy compression.
Note that Carl Zimmer wrote about this exact research in greater detail about a year and a half ago in Discover magazine. Take a look: http://discovermagazine.com/2007/jul/aliens-among-us/ The story even includes the line about "life as we don't know it"!
Now where have I heard this before? Oh yeah! http://www.sciam.com/article.cfm?id=are-aliens-among-us
The world is made by those who show up for the job.
I think you are absolutely right. It seems that many people cannot understand how special the carbon atom is. They assume that our life being based on carbon wouldn't exclude life based on other atoms somewhere else.
Not true. There's a special, unique property in the carbon atom orbital structure that allows very complex structures. No other atom has that quality, unless some basic constants of the universe were changed. It's like comparing a set of Lego blocks with a box of marbles.
The same goes for temperature, to get life one needs a liquid solution that lets molecules interact. With a solid there's no interaction, with a gas the molecules don't stick together, so one needs a liquid for transporting the elements of life. If a planet is too cold or too hot life will not appear. These are some basic limits on the physics and chemistry that will allow for complex chemistry to gradually evolve.
And the funny thing is that we have both theory and experiment telling us that life isn't very common in the universe. We haven't found any sign of life in either Mars or Venus, which a hundred years ago many people thought would certainly have life. If planets like Venus and Mars, that are very close to the Earth in their characteristics, didn't create life, then one should assume that our position is very special.
You can find a brief description here.
The article suggests that the hydrogen was produced only when rocks crack, meaning that the microbes' food supply was meager and sporadic. Now Freund has discovered a chemical process in Earth's crust that may produce enough hydrogen to feed a mass of underground life larger than the mass of all living things at the surface. "[T]he rocks around them will replenish the hydrogen supplyÃÂ--indefinitely, over eons of time," said Freund.
Talk about a shadow life form.
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