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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."
this is how life as we know it uses phosphorus
"nitrogen/oxygen atmosphere"
Without carbon-based life, such an atmosphere would not exist on Earth.
Of course the whole problem with all this is we do not have a good definition for "life" or "intelligence". For example an ants nest can be considered as a single intelligent organisim or a swarm of mindless individuals. The same concept applied on a global scale is what Lovelock's much maligned Gaia hypothesis was all about.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
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.
SIGSEGV caught, terminating
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.
Just look up Extremophiles....
They live practically everywhere including in boiling acid, semi liquid rocks, extreme cold, and on black smokers as above ... it seems that everytime discounts an environment for carbon/DNA based life someone else finds life there ...
I doubt there are many niches for non-carbon based life around for them to exploit on Earth.... other planets may have different forms of life ...
Puteulanus fenestra mortis
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"!
But rocks grow.
My blog
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.
Complex life requires complex chemical reactions. That's why rocks are not alive.
http://en.wikipedia.org/wiki/Life
The most rabid believers in American Exceptionalism are the exact same people whose policies are destroying it.
Yes, and both phosphorus and arsenic are Group V, with 5 electrons in their outer shell so they can be expected to have chemical properties that are similar. But the main material of living things, carbon, will more than likely be the same, for reasons of carbon's unique abilities to form complex compounds.
Silicon-based life with phosphor or arsenic? Apart from this sounding very much like the list of main ingreidents for N-type semiconductor material; silicon, while in Group IV like carbon, with 4 electrons io their outer shell, does not form the same complex molecules as carbon. There is silane, SiH4, analogous to methane, CH4, and silicon dioxide, SiO2, the analogy to carbon dioxide, CO2, and a handful of others, but larger molecules such as sugar or protein analogues just do not form easily from silicon, or fall apart too easily.
There are not that many other elements that possibly oould replace carbon.
SIGBUS @ NO-07.308