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Murchison Meteorite Still Contentious
An anonymous reader writes "The well-known 1969 meteorite that fell 60 miles north of Melbourne, Australia, remains remarkably contentious today. The 100 kilogram carbon rock : a) contains pre-biotic proteins and 12% water; b) harbors 50 amino acids not found on Earth; c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses. While terrestrial contamination (even interior to the meteor) may discount this so-called 'Murchison meteor', its light isotopes of carbon and nitrogen suggest the left-handed amino acids not found elsewhere on Earth have the same ratios as the right-handed ones. This would not be the case if, say, bacteria was just making the left-handed ones after impact. Seems quite a controversy from down-under."
You'd think that after they found what appears to be microscopic life (fossilized, rather) on Mars, it wouldn't be that big of a stretch.
However, it is fairly interesting that that many amino acids are left-handed. Organic molecules tend to form in pretty much the same way in any given environment, so I'd think that if those aminos ARE from Earth, they'd be from someplace strange, like a hydrothermal vent. How they would've gotten onto a meteor from there, who knows.
Guess the DNA spiral the other way just like the water in the toilet down under. ;)
And chunks of it are now on sale at Ned Flander's Leftorium.
Fan-diddly-tastic!
I m just a simple caveman, your fire scares me. These pre-biotic proteins you speak of are unfamiliar to me!
So if the big debate is whether these "rocks" from space contain the building blocks of life, but are being contaminated when they hit earth. Why don't we send up a robot (Or what have you) into space and collect some rocks that have not been on earth?
To me, if you collected about 20 or 30 of these things, it would answer the question rather quickly. Yes, I know that does mean we would get rocks with ammo acids, but sitting waiting for the rocks to come to us seems to be a waste of time.
Linux O Muerte!
.. is find and orifice and pump the meteorite full of shampoo. If all the 'life' on it dies, then it's extra terrestrial. :D
The point is simply that you cannot infer any biochemical 'facts' about extraterrestrial compounds once they've been exposed to Earth's lifeforms.
Try not. Do or do not, there is no try.
-- Dr. Spock, stardate 2822-3.
How would organic material from earth make it into the center of an object like this? Can the force of the impact explain that some how? Just want to know : )
I am a viral sig. Please help me spread.
Perhaps even more interesting (especially if you're already familiar with the debate) is the fact that highlighting a word or phrase on that page causes a browser window to pop up with the results of a Google search on that word or phrase...
Not technically very difficult, but a cool idea...
...Earth. They could be of terrestrial origian and thrown up a billion years ago or so by volcanic activity or a large meteor collision with earth, eventually arriving on earth again after a billion years of orbiting near the Earth. They could be leftovers from a very early time when left handed and right handed life coexisted on Earth.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
.....compared to random or racemic mixtures found in test tubes on Earth. We have yet had no other "lab" from which to study life and it's building blocks (life as we know it: carbon based and mostly made of water). Therefore, the sudden appearence of such components from the stars might very well appear to be "based on dominant left-handed chirality" when compared to the billions-old formula we have here on our planet.
We also don't know how the environment of space will effect amino acids contained in the rock. Since these amino acids (and other material) are foreign, then how do we know that it isn't natural for them to be collected in such a manner?
Never forget the scientific method. You have to ask questions. After you're done asking questions, submit to your peers for them to ask questions.
It really isn't compelling at all. It's similar to how UFOlogists focus on half truths and anamolies that confirm their theories, while ignoring the evidence that shows how 90-95% of all sightings are reasonably explained (the tons of disconfirming evidence). They also turn their nose up to the community and the world, effectively becoming the closed-minded character that they try to call the real scientists: Real scientists submit their work to thousands of peers and accept feedback and analysis. Psuedoscientists do not, and yet they call the critical thinkers that reject their ideas closed-minded.
OK, rant over.
From the article: A curious aspect of Earth's life forms is that they contain (with few exceptions) only left-handed amino acids. In contrast, when scientists synthesize amino acids from nonchiral precursors, the result is always a "racemic" mixture - equal numbers of right- and left-handed forms. Scientists have been unable to perform any experiment that, when starting with conditions believed to emulate those of early Earth, results in a near-total dominance of left-handed amino acids, says George Cody, a geochemist at the Carnegie Institute of Washington.
In many cases, the levorotary forms are lower energy structures and would be favored during synthesis. The fact that many L based systems are almost exclusively so is dependant upon the larger structures that are based upon amino acids and other small molecules. Often a D form of a molecule will not be able to integrate into a L structure.
This is not to say that D forms cannot have biological activity however as there are many instances I can think of where racemic mixtures of molecules can have biological activity. For instance, the 2 chiral forms of carvone have completely different smells due to receptors in the olfactory epithelium being activated by each of the racemic forms.
Some instances of similarity of molecular structure but different chirality have also resulted in catastophies. One only has to think of MPTP poisoning the neurons of the substantia nigra or potentially thalidomide.
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here's a couple of reasons I can think off the top of my head:
1) we've got to get the ship someplace where there are "space rocks". a low-earth orbit really isn't going to accomplish that - you'd have to go to the asteroid belt for a ready supply. that's not easy. or, conversly, you land someplace where rocks may have accumulated (ie, the moon, mars).
2) if you send a ship to a place with lots of space rocks, the ship is going to get hit by a lot of space rocks. shielding becomes a problem.
3) if you land some place, you're stuck getting rocks next to where you land (like viking) or you've got to build a way to move around (like pathfinder)
4) building a reliable, completely automated assay for amino acids is not trivial. if it's mobile, that's going to be even less trivial.
"How many times will science have a victory over the church before we can finally kill God for good?"
What victory over the church? Science is good for proving that things exist, but it's not very useful for proving that things don't exist. If you're drawing the conclusion that God doesn't exist by what is or isn't on a meteorite, then you're not using science.
amino acids not found elsewhere on Earth
Every time I hear this I get rather angry. Are these people really so arrogant as to be absolutely certain that we have already found and identified ALL amino acids, presently on earth? Is there no chance at all, that these same amino acids could be present somewhere (bacteria in deep sea vents, perhaps) and we simply haven't found them yet?
I'm not trying to suggest that, the amino acids found on the meteor are not extra terrestrial. But, I just get angry at these people who seem to feel that they have seen everything that there is to see on terra firma.
This is slashdot, so you're expecting to nod knowingly and pretend you understand it. Or do you really think all those people who discuss quantum mechanics at length really know what they're talking about?
Sounds very sinister. :)
It's quantum physics, you can't know what your talkign about. Reminds me of a /. sig i saw, "Quantum Theory; Calvinball for grown-ups."
"Sic Semper Tyrannosaurus Rex."
The seems abundantly presumptuous. If it broke off of somewhere 4 billion years ago, or even 100 million years ago, it's entirely possible wherever it came from has evolved life and hasn't yet failed.
In fact, it seems odd to me that no one has yet suggested it originally came from Earth. Think about it. As I understand it, there wasn't much of an atmosphere before life, so it's feasible that for one reason or another a hunk flew off. I'm not about to calculate the path it would have flown, or even argue the likelihood, but I don't think it's impossible.
For reference, the nearest star is Proxima Centauri, at ~25,000,000,000,000 miles. I looked a number of places and found no consensus on the speed of the meteorite, but the larger number I saw was 20,000 mph. At that speed it would have taken ~150,000 years to get here. Since that is assuming a straight line among other things I feel it is reasonable to conclude wherever it came from it took longer than that, if it was near a star we know about.
(That really doesn't have anything to do with my point. But I did the research and math so I figured I might as well share it.)
R: That voice. Where have I heard that voice before? B: In about 365 other episodes. But I don't know who it is either.
Case closed and make mine a Foster's. G'day.
Sigs are bad for your health.
c) favors the tell-tale signature of biochemistry based on a dominant left-handed chirality, compared to random or racemic mixtures found in test-tube syntheses.
If a molecule has a carbon with 4 different groups bonded to it then there are two different ways of making the same thing but with different physical layouts eg:
W
|
X -C- Y
|
Z
Or:
X
|
W -C- Y
|
Z
Basicaly these have a "non superimposable mirror image" (no matter how much you rotate them and you can never have all the x,y,x and z's lined up)
Generaly the left handed and right handed molcules have very quite different behaviours, for instance some drugs use only one of the versions, whilst the other version is a poision.
A racemic mixture is a mixture of 50-50 of the left handed and right handed molecules, and generaly chemical processes will produce a racemic mixture.
Fact: the meteorite contains ammino acids, and chirality that is not generally found in terrestrial organisms.
Fact: This meteroite is HEAVILY polluted with terrestrial organic matter.
Conclusion: While ammino acids are generated in space, they seem to mimic the compositions found when we try to synthesize them in the lab.
Aside: You can produce the same results with some methane gas, water vapor, and ionizing radiation.
Move along, no controvesy here.
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Although of course this would be an imense venture, probably requiring a permanent base on the moon and who knows where else, but it would remove the dependency of technology on earth from our fragile ecosystem, and let's face it, we've taken a lot of the easy metals out of the ground, and it's only going to get harder and harder to find. Another important point to remember is that although going up is expensive, going down is dirt cheap. ;)
My two cents. Joshua
When in danger or in doubt, run in circles, scream and shout!
Recent research suggests that there is an excess of L-amino acids (the specific enantiomer used in life-proteins) found in space, suggesting that the chiral specific process involving circular polarized light (mentioned in the article) could have lead to the amino acids that were found on the Murchison (and other meteorites).
...
From the article:
Recently it has been discovered that an excess of L-amino acids is present in the Murchison and Murray meteorites indicating that a preference for L-amino acids existed in solar system material before there was life on Earth. This supports an idea, first proposed by Rubenstein et al. (1983, Nature 306, 118), for an extraterrestrial origin for homochirality.
In this model the action of circular polarized light on interstellar chiral molecules introduced a left handed excess into molecules in the material from which the solar system formed.
If our own solar system formed in such a region of high circular polarization, it could have led to the excess of L-amino acids which we see in meteorites and to the homochirality of biological molecules. It is possible that without such a process operating it would not be possible for life to start. This may have implications for the frequency of occurrence of life in the universe.
otherwise they would be sitting in a detention centre right now appealing their refusal of refugee status by the Australian Gumment. Bloody alien queue jumpers will not be tolerated.