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Scientists have known for a while that the building blocks of Earth life, amino acids, are also found in space. Traces of amino acids have been studied in countless meteorites. But now Arizona State researcher Sandra Pizzarello says Earth amino acids also share the same basic structure with those from distant space. This discovery, announced yesterday in Proceedings of the National Academy of Sciences, could mean that extraterrestrial life would share other structural similarities with Earth life — like symmetrical bodies, for instance — especially if that life had developed from amino acids the way we did.
According to an early release about her scientific paper:
Scientists have long known that most compounds in living things exist in mirror-image forms. The two forms are like hands; one is a mirror reflection of the other. They are different, cannot be superimposed, yet identical in their parts.So the humanoid-looking Star Trek aliens may not be quite so ridiculous after all. Perhaps all amino-acid based life will share the left- and right-handed structure with us. I for one welcome our symmetrical cohorts from this local volume of space.When scientists synthesize these molecules in the laboratory, half of a sample turns out to be "left-handed" and the other half "right-handed." But amino acids, which are the building blocks of terrestrial proteins, are all "left-handed," while the sugars of DNA and RNA are "right-handed." The mystery as to why this is the case, "parallels in many of its queries those that surround the origin of life," said Pizzarello.
Years ago Pizzarello and ASU professor emeritus John Cronin analyzed amino acids from the Murchison meteorite (which landed in Australia in 1969) that were unknown on Earth, hence solving the problem of any contamination. They discovered a preponderance of "left-handed" amino acids over their "right-handed" form.
"The findings of Cronin and Pizzarello are probably the first demonstration that there may be natural processes in the cosmos that generate a preferred amino acid handedness," Jeffrey Bada of the Scripps Institution of Oceanography, La Jolla, Calif., said at the time.
The new PNAS work was made possible by the finding in Antarctica of an exceptionally pristine meteorite. Antarctic ices are good "curators" of meteorites. After a meteorite falls — and meteorites have been falling throughout the history of Earth — it is quickly covered by snow and buried in the ice. Because these ices are in constant motion, when they come to a mountain, they will flow over the hill and bring meteorites to the surface.
"Thanks to the pristine nature of this meteorite, we were able to demonstrate that other extraterrestrial amino acids carry the left-handed excesses in meteorites and, above all, that these excesses appear to signify that their precursor molecules, the aldehydes, also carried such excesses," Pizzarello said. "In other words, a molecular trait that defines life seems to have broader distribution as well as a long cosmic lineage."
ASU Researcher May Have Discovered Key to Life Before Its Origin on Earth [Eurekalert]
Comments
This article fails to take into account the important fact that evolution is just a "theory" espoused by godless liberal scientists. We were created, perfect and unique.
So, not only are there not any aliens, they couldn't possibly look like us anyway.
Just because we may all be symmetrical doesn't mean extra-terrestrials will be humanoid. Octopii, starfish, and platypii, are all symmetrical too.
Somewhere a quadruped race is arguing that the fact that Carbon always accepts 4 bonds suggests that 4 legged life is the natural state...
Seriously the left and right handed nature of amino acids has nothing to do our left and right hands...
This analysis also avoids the possibility of non-carbon-based life-forms, which may have a fundamental molecular configuration which is entirely different from what we would expect of other carbon-types.
do non-carbon-based lifeforms exist on Earth?
judging from the 'aliens' that populate our science fiction it seems almost impossible that they look more like us than we thought.
Radial symmetry isn't the same as bisymmetry, and the majority of complex lifeforms on Earth are bisymmetrical. And it turns out that the genetic coding for bisymmetry shows up even in very primitive, non-bisymmetrical organisms: [arstechnica.com]
But indeed, octopi are bisymmetrical, and sentient octopi aren't that far-fetched, honestly. What is really required to become a sentient race? Enough complexity and size to develop a complex brain or brain-like structure, and the ability to manipulate the environment with a certain amount of dexterity. Niven's Footfall made an interesting case for sentient elephants.
What about hive-minds? You could have millions of small, simple organisms that evolve a genuine collective intelligence. Depends how far you want to push superorganism theory: [blog.wired.com]
Besides octopuses, Dolphins and other cetaceans have demonstrated human-level problem solving skills as well, so it isn't that far fetched to imagine a near future discovery of a water covered world where sea life evolved into a dominant life form. Communicating with them would be a challenge though. First Contact would require a porpoise crew member to translate.
@Gyrus: I think there might be a David Brin book about this . . .
How would cetaceans develop a written language, or use tools? Are we assuming they evolve prehensile appendages at some point?
@zeppelined: Dolphins do have a (semi) prehensile appendage. Well, male ones at least. Ahem.
Let me get this straight... there really could be green hot slave girls from Orion? Wow, it humbles the mind. Also perhaps little gray guys are really kidnapping and probing folks? deep...
@bakana: That's gonna make for some awfully awkward human/dolphin meet-n-greets.
So you're saying that silicon-based lifeforms are just a crazy dream?!?
I refuse to let science squash my imaginary six-breasted, silicon-based imaginary girlfriend!
Phhht! Scientists... what do they know about the universe, anyway...
@ideaman2020: I'm holding out for lego-based life forms. I read about them on Gizmodo.
@Annalee Newitz: ... Hmm. Well, Now I know what I'm going to create when I finally go mad. Living legos.
@zeppelined:
It... already does.
-Kle.
They may not look like us -- compare humans and, say, lobsters -- but this increase the chances that we can eat them.
@cjc: Good point!
Don't forget all the weird stuff found in the Burgess Shale. Hallucigenia anyone?
@LeNoceur:
LeNoceur, you sound as a parody. Evolution might be only a "theory" but it's the best explanation so far how life evolved on earth (or in the universe). What you are quoting is a belief, that has no more value than any other belief. Only a belief. And a belief that is so ridiculous that if it hadn't been swept away by the sentient part of this planet roughly 230 years ago, this website wouldn't probably even exist.
Uh, what? Nothing in that discovery has anything to do with symmetrical bodies.
In fact, the article is very interesting, but in a totally different way: terrestrial processes for making amino acids (and other asymmetrical molecules) fall into two categories: biological and non-biological. The biological ones usually make only one handedness of molecule, basically because protein systems depend on molecule shapes. But as far as we know, (well, as far as I know), *every* non-biological system makes an even mixture of right- and left-handed forms of an asymmetrical molecule. So how is it that we're finding predominantly one handedness in these meteorites? Normally that would be a clear indicator of biological origin...
@Annalee Newitz: You mean like Jesus..?
@cjc: To seek out new life and new civilizations, to boldly deep-fry where no man has deep-fried before.
Seriously, if we can eat them, then they can eat us. And we're not up to interstellar travel yet.
Just popped in to mention that your illustration shows NH on the amino acid, but it should probably have NH2 instead. They sometimes have NH3, but as far as my brain remembers, the only time they have NH is when they've created a peptide bond to a carbon in the formation of an amino acid chain... but that occurs through dehydration synthesis - so the COOH group would just be CO. Also there would be a whole other amino acid attached to the NH group... but all the way at the end of the chain, you'd still have an NH2.
NH2-RCH-CO-NH-RCH-CO-...(repeat until satisfied)...-NH-RCH-COOH
Correct me if I'm wrong. It's been about 6 years since I did any organic chem.
btw, this article is useless without the word "enantomer"
That's "enantiomer".
@fullerenedream: Like I said, 6+ years. I know I've seen it both ways, maybe it's just a common typo, or maybe it's also acceptable?
Either way, I still get a laugh from Brits and their Aluminium, when everybody knows the cool kids all call it Aluminum.
that explains why women are so diffrent yet so similar.-blurey
Biology would work essentially the same way it does on Earth in an extraterrestrial setting...
Plausible.
Therefore sentient aliens would almost certainly resemble almost-human like beings with bumpy foreheads called Worf, no.
It is so refreshing to read that someone else is finally starting to figure this out. I have researched Mars extensively over the last 4 years and have substantive evidence that there were, in fact, (some) Martians that looked exactly like us.
For example, the Mawrth Vallis area on Mars has plenty of artwork made out of rocks that look like us earthlings. Look at the Rover images, look at the satellite images (although one of the best examples you can't find on the web anymore in good resolution). Thank god I saved THAT ONE to my files!
Regards and Peace
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