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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?
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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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the silicone-based rock creature that Spock mind melds with to share its emo about being a rock
Silicone? OMG smart breasts!
(I think you mean silicon).
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You can pry my bottle of Head & Shoulders from my cold, dead, carbon-based hands! Now get those freakozoids out of my beloved state!
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.
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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.
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Oh yeah...
Actually yes. Silicon based life forms, or so I understand (IANA biochemist), are rather unlikely because of the chemical instability of silicon based polymers, but silicone based life forms are a much better possibility.
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wait... not that kind of sig.
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?"
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Two flaws in your argument. First, if such life forms exist in a remote but abundant environment--for example, deep underground--they could be having a significant effect--for example, on geology--that we don't yet recognize. Second, even if such organisms are extremely rare on earth, studying their biology could help us find similar life forms elsewhere. We already know what signatures to look for in the atmospheres of other planets to indicate the presence of carbon-based life, but not necessarily for other biochemistries.
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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 don't know what the original article said (the site is thoroughly slashdotted), but finding life based on alternative chemistry won't "alter the odds" - it will just alter our computation of the odds. That immediately raises my suspicions since it suggests that the article was written by a journalist rather than a scientist, and consequently that it might be severely distorted.
Having said that, there are a lot of possible alternative chemistries that don't involve non-carbon-based life: substituting arsenic for phosphorus as mentioned here need not also substitute something else for carbon, so the most likely possibility is that such life would be carbon based but still "alien." As far as we know now, at Earthly temperatures and pressures carbon is a far more plausible basis for life than anything else, and so far we haven't even found much that's very promising at other temperatures and pressures. But I'm not at all sure that we have sufficiently explored alternative temperatures and pressures to rule them out as possible habitats.
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.
Unfortunately this isn't really evidence of anything, as grasses contain large amounts of silica, presumably for strength and protection. Whether an organism goes down the calcium carbonate or the silica route depends on its habitat. Oysters are "largely calcium carbonate", but they are definitely not a calcium-based life form.
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The meaning is you-less.
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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