Science a GoGo's Home Page Forums General Discussion Not-Quite-Science Forum Aliens Living Among Us?

Aliens 'may be living among us' undetected by science?

Aliens may be living among us, but we do not know it because they are microbes that do not have the standard biochemistry of Earth-dwelling organisms
As well as the many forms of life based on DNA that are known to science, the Earth may have been home to a second creation of organisms that make up an unremarked realm of “life as we don’t know it”, according to Paul Davies, of Arizona State University, a cosmologist and theorist of extraterrestrial life.
“There’s been no systematic search for Alien life here on Earth.
Known life on Earth is based on five main elements – carbon, hydrogen, oxygen, nitrogen and phosphorous – but it is possible that unknown organisms could use arsenic instead of phosphorous. Arsenic is poisonous because it so easily replaces phosphorous in our biochemistry
Some microbes may also have a means of carrying genetic information and replicating themselves that is not based on DNA, or that has extra DNA “letters”. These microbes could exist in extreme environments such as deep underground or in hot springs, or they could even live inside other organisms, including ourselves. “They might be right in front of our noses, or even in our noses,” Professor Davies said.
http://www.timesonline.co.uk/tol/news/uk/science/article5739401.ece

Plus an article, "We Are Not Alone." below.

http://www.timesonline.co.uk/tol/news/uk/science/article5739563.ece

Great stuff this. I am sure that some form of life would have to be found amongst so many planets in the universe. However like one of the responses to the article, I wonder if the lifeform would be so different we would not be able to recognise it. As the writer suggests, life here evolved from the 'stuff' available. if this happened elsewhere with other 'stuff' it would probably look VERY different indeed from earth-based lifeforms. Maybe that is why we haven't recognised them yet?

Interesting.

"There’s been no systematic search for life as we don’t know it here on Earth." - Paul Davies

Whatever the chemical structure of life 'as we don't know it', it would have to be self-replicating (wouldn't it?). Paul Davies suggests that the reason no one has ever discovered a self-replicating molecule, other than those that constitute life as we do know it, may simply be that no one's looked hard enough.

He could be right, I guess. Mind you, I can't help suspecting that if there were such molecules on Earth then someone ought, by now, to have stumbled upon some evidence; some observation of structures that cannot be accounted for. Someone while peering down their microscope, or a geologist analyzing rock samples.

Well, anyway, as they say, where there's life there's hope

Yep, they explained me an Aether theory. But they're not very good in English. You know, E.T.'s...

[quote=Mike Kremer]

I am positive that Redewenur must be correct when he states that a self-replicating life Molecule on Earth should have left some sort of physical evidence behind, that a careful observer should be able to discover?

For dos'nt a self-replicating Molecule of life mean that it is increasing in mass, and leave behind its 'dead' physical presence, ..........that could be detected, with care?
Of course it could have died out, leaving no trace. Or combined symbiotically with another form of life ?

ALL life on Earth, without exception is Carbon based (together with a little Carbon 14)
I find it interesting that of the two dozen or so Meteorites found in pristine Antartica......at least half of them have been found to have microscopic veins of Carbon in them, when cut open under lab conditions. Does Carbon inside a Meteorite signify life ?

(sticking my neck out)
So just how can Carbon be found INSIDE a Martian Meteorite of rock.?
Unless it was once at the bottom of a Martian slimy lake, teeming with algae, many millions of years ago?

Of course not all of the Martian Meteorites so far discovered have Carbon in them.
One of the most amazing discoverys was made by the 'Opportunity Rover' of the only Meteorite ever discovered upon another World.....and there it was, just lying on the Martian surface.!
A 100% Iron-Nickel lump, surely it must have come from the molten interior of an unknown body, after cataclysmic impact, or explosion ?
Picture here:-
http://spaceflightnow.com/mars/mera/050119meteorite.html

Its pretty obvious that there can be no self-replicating life in that Meteorite. Far too molten hot.
But what about this famous Meteorite ? Also found in Antartica, and named ALH4001.

http://nssdc.gsfc.nasa.gov/planetary/marslife.html

Some Scientist believe that it holds the exo-skeletons of nano-sized worms, or nano-Bacteria, that once lived and multiplied within the material that was originally a Meteorite from Mars.

Nano-Bacteria that may not have any Carbon in them, but look like shells, possibly composed of Calcium and Phosphates,
similar to our own bones, could they be the 'life' that we do not know about?

Its interesting that this particular article posits that Clay might be the result of these unknown life organisms, or even that they may be replicating within our bodies today, in the form of Kidney Stones and Arterial Plaque.

http://serc.carleton.edu/microbelife/topics/nanobes/

I believe that Alien life took over the primitive life cells of Earth, many Millions of years ago.
So that we now have Alien life living within our body cells, without knowing it!!
But we now call them Mitochondrion, or Nucleolii, in our ignorance?

As usual, Mike, you raise some interesting points. And as usual, I find myself having to do research, because I suddenly realise that I don't have enough coherent facts in my head to support what I thought I knew!

Meanwhile, have I not read of a hypothesis suggesting that mitochondria were once independent bacteria? Whatever, we can hardly classify mitochondria as being 'life as we don't know it', since they contain DNA (albeit that, in their current form, they contain too little for independent existence).
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edit:

Re your last link, that's excellent. It's the kind of observation that I had in mind. Even so, according to the article there's evidence that those nanobacteria contain DNA - if it's true, then they'll still turn out to be 'life as we know it'. But if it's false, and they really are self-replicating...