From New Scientist

Hmm. Is that actually news or is NS doing the pop-sci thing again?
It does have interesting implications if we would really have to redefine "life"...

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Long-lived prokaryotes, with no predators; if the prime directive for life is just to survive, then these creatures have succeeded.

Perhaps there are many worlds with deep biospheres such as this. I suspect that life of this sort couldn't evolve in situ,; it would need to evolve in a different, nmore active environment then migrate into the depths. Once there, however, a deep biosphere could last a very long time, longer than life on the surface perhaps. And presumably with the bare minimum of reproduction, and therefore no evolution to speak of.

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It would not be unlikely to find this on Mars, then? If life ever evolved there, that is.

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[Foot mouth in put]
Si tacuisses, philosophus mansisses.

Quick! Let's put 'em on the menu! Mmmm... Prokaryotes...

(And... can we make fuel out of them?)

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How likely is it, that this life would not be related to ours? (meaning: not coming from the same pool of 'dead' matter turning into life?)

Is there a way to tell? (if there would be several independant ecologies known to us, could we see e.g. an oak tree and a crab would come from the same source?)

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Neptune, Titan, Stars can Frighten...

We look at the DNA. Most creatures on this planet share portions of their DNA with on another.

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And I assume it is still totally open to speculation whether alien life would or wouldn't be based on DNA, or on a similar yet different method to contain genetic info?

Did scientists check the DNA of the extremophiles (of the article the OP quoted, and/or others)?

BTW I am acquainted with the Panspermia hypothesis. (Hey, I invented it when I was a kid and needed an explanation for all those all too human-looking aliens in Star Wars and the other stuff I watched...) Is there a name for the hypothesis there were several origins of (unrelated, at least genetically) life on earth?

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Neptune, Titan, Stars can Frighten...

There was, a couple of years ago, speculation about the possibility of a 'shadow biosphere', which either evolved separately from the main biosphere or arrived from space (Venus or Mars most probably, perhaps elsewhere).
http://en.wikipedia.org/wiki/Shadow_biosphere

As far as I am aware, all organisms on our planet can be linked by molecular phylogenetics, and there is no shadow biosphere- but I don't know if these deep hot microbes have been tested yet. (I suspect they have).

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They made a documentary about this stuff, it's called The Abyss, but I liked the earlier documentary on the subject called 2001: A Space Odyssey.

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Alien life my have DNA equivalent molecules, but it won't be earth DNA and will be quite obviously different.

The DNA of all sorts of life has been checked out to varying degrees and it has all been the standard earth model.

Unless it has the same origin (suppose life originated on Mars, and then somehow went to both Earth and Europe. I'm not saying I find this likely; I'm just supposing.)

Does that necessarily prove a common origin (this is what I think is most likely), or might it also lead to the conclusion (or at least leave open the possibility) that there 'simply' isn't another way (meaning that if, wherever, whenever, life originates, it will always be through standard DNA)?

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And if it didn't, then we might suspect life having been transported via meteoric impact.

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I always find it amazing how resistant people are to the concept that every tetrapod on Earth is a hyper-evolved fish. They look at a Thompson's gazelle and just don't see it.

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