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Using Light's Handedness To Find Alien Life
Rational Egoist writes "Scientists working at the National Institute of Standards and Technology have come up with a novel, easy way to detect life on other planets. Rather than try to measure the composition of atmospheres, they want to look at the chirality of light coming from the planet. From the article: '"If the [planet's] surface had just a collection of random chiral molecules, half would go left, half right," Germer says. "But life's self-assembly means they all would go one way. It's hard to imagine a planet's surface exhibiting handedness without the presence of self assembly, which is an essential component of life."' And they have already built a working model: 'Because chiral molecules reflect light in a way that indicates their handedness, the research team built a device to shine light on plant leaves and bacteria, and then detect the polarized reflections from the organisms' chlorophyll from a short distance away. The device detected chirality from both sources.' The article abstract is available online."
What if the aliens are ambidextrous?
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if you had to google chirality
What 'handedness' is earth? I think that because of the vast amount of life on our planet, the handedness would be (statistically speaking) about the same in both direction
As far as I know, all known life on earth is left handed (i.e. built from left handed amino acids)
What 'handedness' is earth? I think that because of the vast amount of life on our planet, the handedness would be (statistically speaking) about the same in both directions. According to the article, the handedness gets inherited from parents but it doesn't make clear whether or not it is the same for all life forms.
The last several articles that interested me also did a terrible job of actually explaining anything. It's surprising that some of the information omitted consists of very basic details that are directly related to the headline. I hope this isn't the beginning of a trend; infotainment and the average press release have done enough damage to journalism already.
It is a miracle that curiosity survives formal education. - Einstein
What 'handedness' is earth?
I have no idea. But I'm not sure it matters. Even if Earth was perfectly neutral the method still works. If the presumption is true then any planet significantly away from average would indicate life. Even if it wouldn't find planets with life that were average.
Life on earth exhibits a specific "handedness" or chirality. All DNA twists the same way, for example. Apparently the term for this is homochirality.
http://en.wikipedia.org/wiki/Homochirality
Ummm... "They already have a working model". That sort of made it seem like you know, maybe they had something that they could use at a range of more than a few FEET. This is a long way off. And maybe not even theoretically sound? Sounds little early to be news.
CBC's science program Quirks and Quarks had an interesting story about the handedness of molecules that it played last month. (Audio available in Ogg Vorbis) It provides a nice, friendly introduction to this topic.
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The chirality ('handedness') of all known forms of life on earth is the same. Your enzymes can work on certain biomolecules but will not work on their mirror image (a molecule with opposite handedness). Once enzymes are fully formed to do a particular task, there usually isn't much selection pressure to evolve another enzyme to make the same products on mirror image biomolecules. As a result, handedness has been conserved throughout evolution and all organisms share the same handedness with respect to what forms of biomolecules they can process and produce.
This sound very interesting. Maybe there are business opportunities with Aliens. What do you think they would be ready to buy from us? Maybe something to show an even distrubution of chiral molecules could avoid their friends on other planets to also get discovered by nasty sellers from Earth, but I am not sure we should sell such a thing. Any valid business idea?
So, to sum up the article... Chirality is not dead!
One more trek concept brought to real-life, yay! (The other one being the communicators on TOS)
- AC, patiently waiting for warp drives
Smells of a "fund me, or PhD me" non-story.
Also possible: "Buy my freaking huge flashlights!"
Anyway, I guess a star would work as a light source to.
This just might work. It'll take incredibly good optics, of course, and the chirality of the light from these distant planets might be lost when the light goes through the earth's atmosphere. Might take a gigantic telescope in outer space.
Amino acids are "left-handed", but most sugars are "right-handed". Would that even out in the end?
The whole reason that life produced molecules of fixed chirality is that molecules precursing life are generated in cold gase nebulae that are often effected by radiation from young stars which have a particular chirality. That is to say, the cold nebulae that was the precursor of the Sol system, had light whose chirality precipitated right handed sugars and left handed amino acids.
A planet let's say, made of hydrocarbons and complex organic molecules that formed in such a cold dark nebulae, might have no life, but it's chemistry would in fact have fixed chirality. That is to say, someone needs to point the first instance of this instrument at Titan, a place where we are pretty sure no surface life (as we know it) might exist, but whose surface chemistry may very well have preserve some of the chirality of the nebulae that formed the Sol system. If we receive significant chirality frozen in the Titan surface, it would be a strong indicator that this test is less than optimal for finding earth like planets.
Actually, rough guess here of course (IANAPHD on the subject), I don't think that's the main problem.
Detecting light reflected from a planet at any interstellar distance is a bigger hurdle. We still mainly detect extrasolar planets indirectly, either by gravitational effects, or by occlusion. (For the curious, this is also where the bias in favour of detecting very large planets arises; the bigger they are, the easier these methods can be used to find them.)
Detecting light from a planet is a pain, since they are not inherently luminous to begin with; they reflect light only. Meaning the more luminous the star is and the closer the planet orbits it, the brighter the planet appears to be. However, as those values rise, so too does the glare of the starlight, making detection harder in the process.
A candidate world needs to be in the habitable zone, reflecting light that can be distinguished from the star it orbits, and detectable to optical astronomy at interstellar distances. There are no telescopes yet that can do this, nor have we found a planet that I know of that fits the above criteria.
If we had the equipment, somewhere to point it, and the means to analyze the image precisely enough, then we could do this. They're basically talking about spectral analysis of telescopic imagery; we've gotten halfway decent at that in the last thirty years. We might even get to use this method in my lifetime.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
First, for those who are wondering "What the heck is chirality?". So, you have left handed gloves and right handed gloves, and you can't transform one into the other without doing something like flipping it through a fourth spatial dimension (strangely, flipping it through the time dimension will result in an opposite handed glove traveling backwards in time that's made of antimatter) or turning it inside out. Proteins, also being three dimensional objects, are the same way. And there is a convention for deciding whether a given molecule is right or left handed. Chemical processes tend to produce equal numbers of left and right handed versions. Biological processes on earth tend to produce almost exclusively right handed molecules.
I didn't know this before reading the article, but it makes sense... the chirality of a molecule apparently affects the polarity of the light that is reflected from it or transmitted through it.
Now, to talk about what I think of the article...
Scientists make too many assumptions. Life requires self-replication... that's it. It doesn't require water and it doesn't require chirality. It doesn't require a whole host of things that scientists tend to assume it requires simply because it's a characteristic we've observed about life on earth.
But, I will agree that if they can detect the predominance of one particular chirality then that's a strong indicator of some life-like process at work.
That absence of chirality is no indicator that there isn't life. It just won't resemble the life we have here on earth.
It may be possible to prove that self-replication within a given system (like chemistry, for example) is very hard without certain conditions. I'm willing to believe, for example, that non-carbon based life that primarily functions chemically is highly unlikely because carbon is such a fantastically versatile atom chemically speaking.
Of course, there might be life based on nuclear processes or, even farther fetched, life based on gravitational processes. As support for the second, galaxies have a very complex lifecycle in which supernovas and black holes play key roles. They eat the thin gas left over from the big bang, and metabolize it into new stars with supernovas and black holes. I'm not sure where self-replication fits into that picture so galaxies may just be metabolism absent a mechanism for self-replication (i.e. engines) and hence not really alive.
Life based on nuclear processes or gravity is certainly not going to exhibit any chirality signature, nor require water or even carbon.
But, as I said, I will agree that a chirality signature is strong evidence for chemistry based life. I just don't think its absence is strong evidence against life.
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If we can't actually go visit any aliens we detect because they are light years away, it is just going to drive us batty.
And I don't really want the aliens coming to visit us either, because that would mean they were more technologically advanced than humans. And the inferior species always seems to end up as food or raw material. Come on, even Hollywood has figured this out!
Further research shows that I'm wrong about the chirality of life on earth. Apparently left and right handed aren't used as such in biology. Amino acids, and hence proteins have L- chirality and sugars have D- chirality.
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I suppose that if you were to detect chirality bias in the light coming from a particular planet, that would probably be sufficient to conclude that there might be some form of life on that planet that was causing that particular bias. However, it doesn't seem that it's a necessary condition, i.e. not detecting chiral bias might mean that there might after all be some very strange life form on the planet whose chemistry made use of both left and right handed molecules. In fact, there are some strange life forms on Earth, notably archaea, that actually use right-handed proteins in some aspects of their biochemistry, quite unlike all other life forms found on earth, which use left-handed proteins exclusively.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
Transit.
As a planet passes between us and the star some (very) small amount of light from the star passes through its atmosphere, including incident grazing of the surface. If/when the detectors on a space telescope are sensitive enough, then, during transit they may detect a change in the distribution of polarization. This may also be easier when the transit is either just beginning or just ending, since the main source of light will be mostly "to the side" of the planet.
As the sensor density increases, we should also be able to look at the small number of the atmospherically-affected nodes and ignore the surrounding unobstructed stellar light nodes.
That's what THEY want you too think.
Oops, I've said too mu[NO CARRIER]
Qxe4
Surely this would be a good test to check out Europa?
Even though the ice crust might obfuscate things, if the light was from reflected from the area of a crevice/crack then there would be elements (or the lack thereof) in the frozen water that give some indication.
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>As a result, handedness has been conserved throughout evolution and all organisms share the same handedness with respect to what forms of biomolecules they can process and produce.
The fact that all life on earth comprises molecules of the same handedness is one of the myriad of strong pieces of evidence that the theory of evolution is correct in its prediction that all species evolved from common ancestors. The chirality of the basic molecules of life just has to be THE most fundamental characteristic that any lifeform can have. The fact that all life on earth is composed of molecules of the same chirality is a reasonable indicator that all life on earth is descendent from a common set of primodorial self-replicating molecules ... possibly even just the one molecule that started it all off.
I have no idea, but I'm not sure it matters. The method still works even if Earth is perfectly neutral--if the presumption is true then any planet that deviates significantly from the average must have life; although, those planets might not be typical of ones with life.
You appear to be wrong on a few big things...
-most compounds are not chiral, so even if a dead planet had some pure enantiomers, they would be insignificant compared to one with life, life produces a crazy large amount of them
-no one has quite figured out why life has the handedness it does, some say it could be because of silicon catalyzing a certain handedness, others disagree, there is not an answer to this question yet, but it makes sense that life would evolve to have a specific handedness so all the parts could be interchangeable and we don't have bizzaro ecoli floating around that can exchange DNA with normal ecoli
-since when does polarized light catalyze chiral reactions?? UV light can catalyze reactions, and chiral molecules can cause a reaction to form with a specific handedness, but only chiral MOLECULES can catalyze reactions to cause a more enantiomericly pure product
Based on the little-known work of Dr. Peter Pullet-Wildly, it should be possible to detect not just alien life, but alien intelligence. Because if you encounter left-handed rather than right-handed chirality, it feels like somebody else.
Unless you're a southpaw, of course.
I've calculated my velocity with such exquisite precision that I have no idea where I am.
That would be an immense technological feat. Where already doing something similar with a telescope that looks for planets by seeing the slight dimming of stars caused by the planet eclipsing then star. It was compared to seeing a fly pass by a headlight a mile away.
Detecting a minor variation in the handedness of the light that the planet happens to catch on the surface then reflect back into space, which is light years away, whose feeble light is VASTLY over powered by it's home star. I'm guessing will have to wait many years for this, and there maybe a more feasible technique that comes along before it.
By using a combination of rice paper and domestic household bleach you can detect if a planet is either Regular or Goofy footed...
Task Mangler
I like the idea. It looks like an execellent tool to add to the toolbox for determining the probability of an extrasolar planet harboring an ecosystem.
Of course, an alien ecosystem could have evolved to use both handednesses, but the information that one handedness is predominant on the planet is a strong hint that there's something unusal going on there. Same goes for the detection of unusually large quantities of unstable substances (oxygen, halogens, etc) in the atmosphere of the planet.
Using Light's Handedness To Find Alien Life
Because the heavy handed approach we've taken so far is not working?
Oh wait...
-= This is a self-referential sig =-
The notion that chiral molecules polarize light is not the contribution of this research. Anyone that has taken an introductory organic chemistry course will know this property of chiral molecules to be true. Also, those involved with "origins of life" research are certainly aware that looking for this type of light might be our best bet at discovering alien life. The idea is not novel. The approach is. The paper they reference is titled: "Detection of circular polarization in light scattered from photosynthetic microbes" Which focuses on the approach to detection, not the novelty of what the detection might implicate.
The habitable zone is not fixed in stone, we could perhaps find life outside of it. It would be worth examining chirality for any planet. Still, not much can be done until advances in astronomy let us get a decent view of these exoplanets.
That is a very weak cup of tea. For one thing, I can't see what is new in this; we have been able to do this sort of thing for decades. Also, I don't think we would be able to detect life on Earth using this method, let alone another planet lightyears away. The biomass on Earth is actually rather minute compared to the whole of the atmosphere or the oceans, so the signals would be weak, even for our own planet; and there are many things between us and our neighboring stars that could both polarise and depolarise the light on the way, thus scrambling the signal.
To me this sounds like cartoon science.
Not nescecarily, you cannot directly infer the handedness of the reflected light from the handedness of the molecules, L-amino acids and D-sugars might have the same handedness at some frequencies.
But IIRC, the handedness goes way up close to absorption bands, so coloured compounds will account for most of the handedness of the reflected light of a planet. It seems reasonable to assume that the main light-harvesting molecule (chlorophyll in the case of earth) will account for most of the handedness of a planet.
...is that life forms a kind of amplification process.
If you have some random soup of molecules formed by abiotic processes then apart from some small biases brought about by parity-violating fundamental physics we expect complete symmetry between left- and right-handed molecules.
But life, arguably, forms a kind of amplification process. Competition between molecules with different chirality might serve to increase any initial small difference between one group and another. So what starts as almost exact symmetry results in a planetwide bias one way or the other.
But there are two issues.
(1) Could such a planetwide bias show up strongly enough in the polarisation of light reflected from the planet. It seems very unlikely given how messy a planet is. Let's say you pick a million different types of molecule than come in chiral pairs and for each molecule pick one of the pair, discarding the other. Now jumble up many different copies of each of these molecule types. Your chances of detecting chirality from afar is minimal even though, in some sense, the mixture is perfectly chiral, because of the overall randomness of the mixture.
(2) Could any other physical processes cause such amplification? The answer is yes. For example some kinds of crystal growth can result in homochirality.
So I'm pretty sceptical despite the idea being neat.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
-since when does polarized light catalyze chiral reactions?? UV light can catalyze reactions, and chiral molecules can cause a reaction to form with a specific handedness, but only chiral MOLECULES can catalyze reactions to cause a more enantiomericly pure product
Not quite, IIRC, there are examples of some reactions with polarized light which gives ~1% excess of one enantiomer. It has been hypothesized to be the origin of the handedness of life. But in itself, it will not give enough of a excess to be meassured with this technique.
However, I'm surprised to learn we collect enough light from a planet to be able to authoritatively assess chirality.
[FUCK BETA]
As far as I know, all known life on earth is left handed (i.e. built from left handed amino acids)
When I read the GP, I jokingly thought to myself, we are inherently evil so we must follow the Left Hand Path.
Funny to see life on this planet is actually wired for evil.
How amazed would you be to suddenly find that you just forgot what I wrote and you needed to reread my post.... again.
-no one has quite figured out why life has the handedness it does
I recall a theory that it is due to the slight asymmetry in weak interaction, but I've forgotten the exact mechanism. This asymmetry exists basically everywhere in the universe, but as life is self-replicating, it can amplify the effect to a great extent. Here's the first reference found via quick googling:
http://www.springerlink.com/content/0743577n4716u23j/
Escher was the first MC and Giger invented the HR department.
I recall a story about it, someone in this thread linked to a Quirks and Quarks story where it turned out that comets have been shown to have a tendency to lean towards containing amino acids with a certain handedness. The thought is that life likely formed with that handedness because there were more amino acids to work from.
Of course the star will function as the light source, but as I understand the current method of finding exoplanets is looking for regular fluctuations in star spectra caused by their orbiting planet(s). In order for *this* to work light reflected on the planet needs to be intercepted.
No, it didn't do well because it sucked. It had a clever conceit, yes, but what happened for the remaining hour or two was your typical action movie, only without the effects budget.
I am trolling
reflections of light
our query: is it life jim?
- not as we know it
- I choked on the red pill and now I'm stuck in limbo
When did that happen and why wasn't I informed about it?
Mit der Dummheit kämpfen Götter selbst vergebens
>As far as I know, all known life on earth is left handed
Your left or my left?
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Sounds little early to be news.
One of the points of "the news" concept is the delivery of the information as early as possible and as soon as it happens.
That is one of the reasons we call it "the news" and not "the olds".
Mit der Dummheit kämpfen Götter selbst vergebens
Also, don't forget racemization (http://en.wikipedia.org/wiki/Racemization) - a lot of enantiomeric compounds can spontaneously switch chirality (it's actually a big problem for some extremophile bacteria - they replicate so slowly because they have to expend energy to repair damage from racemization).
The other left, of course.
Material from space has already been shown to exhibit chirality. There's quite a nice review on...
http://scienceandreason.blogspot.com/2009/04/amino-acid-chirality.html
We do not know that this chirality comes from life. People have presented this as evidence that life exists in space, that life was seeded from space, and all sorts of other stuff. All we actually seem to know is that some stuff out there shows a handedness. If your light is passing through chiral material in space it will pick up a polarization.
This is not to say that this is not a test. If we find a star with planets, and one of the planets reflects more of one circular polarization than the other, then whatever it is that was doing it is probably on or about that planet. A good start would be to see whether we can pick out earth from space this way. I think they are planning to do just that.
[Laughs] Right, kick ass. Well, don't want to sound like a dick or nothin', but, ah... it says on your chart that you're fucked up. Ah, you talk like a fag, and your shit's all retarded. ...
Don't worry scrote! There are plenty of 'tards out there living really kick ass lives. My first wife was 'tarded. She's a pilot now.
I thought it was a hilarious movie : )
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There was a recent discovery of a planet in what is considered the "Habitable Zone" Gliese 581. This is 20ly from Earth. Doesn't necessarily mean they can detect light off it though.
Laughter is the best medicine, except if you have a broken rib.
If life evolved from simpler forms then one would expect each species to inherit the handedness of its ancestors, all the way to the very first living being.
OTOH, if life was designed by a creator, then one would expect that creator to have some preference for one handedness over the other.
Article summary is incorrectly attributed to "Scientists working at [NIST]." Out of the 12 authors of the report, only a single author [Gerber, author no. 4] is affiliated with NIST, which issued the press release. The first author of the report is William Sparks, who is based at the Space Telescope Science Institute in Baltimore (3 authors). The remaining authors are based at
* Center for Astrophysics Research (University of Hertfordshire) (2 authors),
* Department of Astronomy (University of Maryland),
* Center of Marine Biotechnology (University of Maryland Biotechnology Institute) (4 authors),
* Canada-France-Hawaii Telescope.
I requested the full paper but... as we are friday afternoon here in Europe I'll probably get it on Monday ;-)
In the meanwhile, from the abstract I feel this'll be more applicable to say checking remotely life hints in Jupiter's atmosphere here, than getting answers for remote stars tomorrow.
I for one highly doubt, for instance, that just analysing an exoplanet's transit onto its star will bring any measurable polarization. ;-) it'll be very difficult to detect the ppm of added polarization.
Just remember what you see is star light that passed through the planet's *atmosphere*, not reflected onto its ground (and grass/trees).
And as this specific light is moreover buried within the 99,99% of starlight that just didn't cross the planet at all, even with a specifically intense *atmospheric* life (a dense, GREEN atmosphere
Rather, I see this either for
a) a futuristic payload for the (too futuristic) Darwin project from Esa/Nasa ( http://www.esa.int/esaSC/120382_index_0_m.html/ ), when the dozen of years of development (and equal number of euro and dollar billions) will have been invested: if things go well, no more crises, etc., we then will have a way to just switch the starlight off (via destructive interferometry), and see only planet's light.
Then maybe you'll measure polarization. But then you'll also measure specific wavelength absorptions, so get directly to molecules (which is the raison d'être of the Darwin project)
b) as said earlier, maybe in nearer times a way to observe our neighboring planets atmospheres, and suddenly discover they may be polarized (or not, and that check will be quick).
If they were it'd definitely be fun.
In my space factory there is a breadboard of the Darwin nulling interferometric concept. Nifty. Representing maybe 1% of the required development work. But nifty, definitely: capable of switchig off a star light that is millions of times superior to the planet's reflected light and at the same time leave planet's light in, when planet is just the pixel against the star's one. As they say on Esa's site, capable of seeing a candle light stuck against a lighthouse firewindow, from 1000 km away.
Herve S.
This is the basis for creating artificial sweeteners. Sucralose contains mostly dextrose, which is a mirror image of glucose. They have the same chemical formula, but since it's of the opposite chirality of all the other structures in your body it's unable to be metabolized.
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From wikipedia:
The origin of this phenomenon is not clearly understood. It is even unclear if homochirality has a purpose.
So I guess its not fairly obvious. What exactly makes it obvious that a mirror image of a molecule wouldn't function exactly the same and therefore be found in the same quantity as the other?
Converting food sources (proteins, molecules) from left-handedness to right-handedness and vice versa is going to take more energy than just having the same handedness as the food source. Whichever food source became dominant would eventually force everything else up the food chain to have the same handedness. In the end, everything would flip to one state or the other.
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This is the basis for creating artificial sweeteners. Sucralose contains mostly dextrose, which is a mirror image of glucose. They have the same chemical formula, but since it's of the opposite chirality of all the other structures in your body it's unable to be metabolized.
The body can metabolize dextrose (d-glucose) just fine (in fact, it's the l-glucose that the body cannot metabolize). Sucralose, on the other hand, is a different molecule since it contains chlorine atoms in some of the places where sucrose contains HO groups. Sucralose is also about 600 times sweeter than sucrose.
OK, so we just have to determine the color of the main light-harvesting molecule of extraterrestrial life forms.
And hope that the planet doesn't have an advanced-enough civilization that the main light-harvesting objects on it are solar cells. :-)
The Tao of math: The numbers you can count are not the real numbers.
If we discover life that is of opposite handedness to the life on this planet, then they wouldn't be able to eat us. :(
On the other hand we wouldn't be able to eat them
but on the gripping hand thry could still hunt us for sport. (or we could hunt them for sport.)
Actually there are forms of DNA that twist in a right handed manner and a left handed manner. But of course that has little to do with chirality.
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If this method for detecting life works well then you better believe any advanced alien civilization relatively close to us probably already knows exactly where we are. Perhaps we should hope that life is so common in the universe that they are working their way down a long boring list of warm wet rocks with weird crap growing on them and it will take them a long time to investigate us.
"If the [planet's] surface had just a collection of random chiral molecules, half would go left, half right," Germer says. "But life's self-assembly means they all would go one way. It's hard to imagine a planet's surface exhibiting handedness without the presence of self assembly."
He's not talking about life, he's talking about Earth life. We have only one data point to go by, which is too little to draw generalities from.
It is perfectly plausible that a biosphere could be bichiral. There could be parallel but non- or weakly-interacting ecosystems, or one ecosystem with organisms that exhibit both. False negative.
There could also be monochiral planetary surfaces due to the process of catalysis of organic but non-biological compounds. False positive.
It doesn't make sense to me to look for extraterrestrial life by looking only for the characteristics of terrestrial life, any more than we should look for extraterrestrial civilizations to be comprised of humanoids or even humans. "The problem with aliens is, they're alien." (Greg Benford? Larry Niven?)
"I may be synthetic, but I'm not stupid." -- Bishop 341-B
Parent is abrasive, but I think his point is probably correct.
I'm not an astronomer - but I'm a biologist and we do circular dichroism measurements on biological samples (wikipedia article is good enough: http://en.wikipedia.org/wiki/Circular_Dichromism).
The notion that you could detect these signals from an exoplanet lightyears away - given that we can't, at the moment, detect light from such planets at all - strikes me as somewhere between far fetched and complete bullshit.
On the other hand, as a device on a mars rover (or even a satellite probe, maybe, although I doubt this would work through the atmosphere) this makes a lot of sense. So tag this as xenobiology rather than astronomy and we're maybe okay. Can't say more without reading the actual paper.
The good and new comes from no quarter where it is looked for, and is always something different from what is expected.
The planet Zorran, neighbor of Tattoonie, has an interesting biology. The left handed chirals evolved into the plants and the right handed Zorrans evolved into animals. How do the animals digest the plant matter you ask? Well their mitochondria is actually ambi-chiral called mitachloreans. Thus the light reflected by Zorrans has both left and right handed chiral-photons.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Why is that obvious? It seems obvious that left and right handed molecules should be useful for different things like the Z and S blocks in Tetris, but why should one be discarded entirely?
.evom ton seod gis eht
The answer is that two mirror image mollecules won't necessarily fit into the same chemical receptor (think Tetris), and therefore have different biochemical effects.
Codene is actually the stereoisomer of heroin, but it doesn't fit most of our receptors so appears mostly inert.
Jeremy
I agree that chirality implies some kind of autocatalytic process to amplify weak natural chiral bias or statistical fluctuations, but I don't agree that it is diagnostic for life. After all, crystals self-assemble, so a planet dominated by large crystal structures could be highly chiral.
Self-assembly is only part of the definition of life--there also needs to be mutation, and the mutation has to affect the propagation of subsequent generations.
It's not that one set is discarded, it's just never assembled to begin with. The GP is clearly talking out his ass with the "selective pressures" thing. The fact of the matter is, most molecules used by life forms are assembled by life forms, going back to the original replicator molecules that were the progenitors of life today. When replicator molecules replicate, they make copies with the same handedness as themselves. So, if the progenitors of life on Earth were left-handed molecules, all life on Earth will be made from evolved versions of those left-handed molecules. In order for there to be both left and right handed life, life would have to had arisen at least twice, independently, and the two forms of life would be utterly unrelated to each other evolutionarily. The fact that all life on Earth is left-handed is one of the best pieces of evidence for the notion that life only arose on Earth once, and all life today is descended from that. It's possible it arose twice and both happened to be left-handed, of course...
"Convictions are more dangerous enemies of truth than lies."
It's possible it arose twice and both happened to be left-handed, of course...
That's interesting. I wouldn't be too surprised to find a very localized think like Archaea that could be traced to a different source. (Well I would be surprised, but I wouldn't be "That's impossible surprised")
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OTOH, if life was designed by a creator, then one would expect that creator to have some preference for one handedness over the other.
Why would you expect that?
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I've been aware of light fingered aliens for a long time. I have half a drawer of unmatched socks that constitutes proof of their existence.
We need a "+1 -- nice sig" moderation.
In Latin, "left" and "right" are "laevus" and "dexter", hence the L and D for left and right handedness.
I think [s]he knew what the L and D stood for... the comment "I was wrong" referred to the statement that "Biological processes on earth tend to produce almost exclusively right handed molecules."
Life on earth exhibits a specific "handedness" or chirality. All DNA twists the same way, for example. Apparently the term for this is homochirality.
Sounds kinda gay to me.
I do not support "The Man". I also do not support your irrational stupidity
Hmm.. does this extend to bacteria, viruses, and so on? I wonder if it wouldnt be possible to coexist with a species from an opposite-chirality world, and not fear the otherwise inevitable mutual death by deadly plagues.
Think of the movie War of the Worlds. Dropping yourself into another inhabited planet would probably be a death sentence as your body would have no resistance to the kinds of viruses and bacteria that live there. But could having opposite chirality make you immune to their effects?
So, this would be evidence against the notion that life was created by the FSM. Perhaps the "research" is part of a plot by evil pirates. Or would that be evil ninjas?
"Convictions are more dangerous enemies of truth than lies."
Right. In fact, it's an interesting system. There's a planet in it that we have seen by the light reflected off of it, but that planet is not in the habitable zone. There's also a planet in the habitable zone, but we detected that one by more indirect means. So, close, but no banana...
We're getting close, though, to getting all those parameters to line up. So it's nice that we have this new test ready for when we finally find a good candidate to use it on.
"Convictions are more dangerous enemies of truth than lies."
The notion that you could detect these signals from an exoplanet lightyears away - given that we can't, at the moment, detect light from such planets at all - strikes me as somewhere between far fetched and complete bullshit.
This would be where you're "I'm not an astronomer" is showing. In fact, we can and have detected light from exoplanets. We've even done spectral analysis on some of them to discover their atmospheric composition. So, there's nothing at all far fetched about this.
"Convictions are more dangerous enemies of truth than lies."
Codene is actually the stereoisomer of heroin, but it doesn't fit most of our receptors so appears mostly inert.
Codeine and heroin are not stereoisomers. They have similar morphine-based structures, but not the same composition. Methylmorphine (codeine) is C18H21NO3. Diacetylmorphine (heroin) is C21H23NO5.
The more famous example is thalidomide. One isomer causes birth defects. The other is effective at countering morning sickness.
But then again, I could be wrong.
This reminds me of the book "Spock Must Die!"
Spoiler warning!
In the book, a long distance transportation of Spock goes wrong (the beam is mirrored back to the ship), and a duplicate Spock is created. A lot of the book involves trying to figure out which is the "real" one in combination with solving the other issues. At one point, it is discussed that the copy was likely a mirror image. Eventually the evil one is found by noticing that he does not eat regular food, because his chirality is reversed, as the mirroring goes done to the molecular level.
Think of the movie War of the Worlds. Dropping yourself into another inhabited planet would probably be a death sentence as your body would have no resistance to the kinds of viruses and bacteria that live there.
Probably not, actually, since there's no reason to think that you'd be a similar enough environment to whatever they usually lived in. Smallpox was bad for the native americans not just because they weren't adapted to it, but mostly because it was adapted to humans.
Of course, you could still end up dying when you find out that the atmosphere there has cyanide or hydrogen chloride or something instead of oxygen.
OTOH, if life was designed by a creator, then one would expect that creator to have some preference for one handedness over the other.
Why would you expect that?
Compatibility?
No, the windows viruses are still nasty.
You are being MICROattacked, from various angles, in a SOFT manner.
I had always wondered how they detected lifeforms - even one or two lifeforms on an otherwise desolate planet - in Star Trek, Star Wars, and the like.
Now I know.
Incidentally, I'm right handed.
Well, if you're building a system with base organisms that are food for higher level organisms, which are food for even higher level organisms, etc. then having the wrong handedness means you cannot participate in the chain.
How does a left handed cow eat right handed grass? Furthermore, how would a right handed tiger eat a left handed cow?
They try to use it as evidence against a creator and for evolution, but that doesn't make much sense, since a creator would have to build two separate and completely incompatible eco-systems. It makes more sense to make just one that is fully inter-dependant and self-supporting.
Actually killer evidence against a creative entity would be if it were found that we did have more than one biological system on the planet - one right handed and one left handed. They would eventually merge into the two regardless, and in truth one would probably eventually eliminate the other, but there is no reason evolution shouldn't initiate more than one system. In fact, it should have initiated millions of them, which eventually "stuck" and were able to flourish. This would almost guarantee two systems, at least in the beginning.
Anyways, those are just my thoughts. The handedness of molecules is new to me.
Security is mostly a superstition... Avoiding danger is no safer in the long run than outright exposure. - Helen Keller
You're right. On a closer reading, it seems that the article doesn't quite say that archaea need to have used enzymes made up of right-handed proteins in order to generate the right-handed glycerol groups which make up part of their cell walls. Then again, the biology of archaea is still poorly understood. Nevertheless, their use of such a right-handed organic molecule in their cell membranes, where everywhere else in life on earth similar molecules are left-handed, is one example of the case I describe. If we had a planet where the dominant life forms were archaea (right-handed glycerol groups in cell walls) and bacteria (left-handed glycerol groups) in more or less equal numbers, might not the detection method fail to find any chirality bias in the light from the planet? This may have been case in the young earth when life first began to evolve.
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
Correct. It pretty much has to go one way or the other; your left-handed critters like all of us cannot eat right-handed things and process them.
When greeting aliens, shake with left hand.
But seriously, it's an exceptionally interesting thought that there might be a 'biological life scanner' like the kind seen in Star Trek, WALL-E, and other science fiction of the sort.
I suppose it depends on the kind of chemical reactions involved. I don't know much about chirality, but I'm guessing the reason we can't digest those molecules is because our enzymes are the wrong shape to link up to them and rip them apart. But if an alien pathogen produced highly reactive compounds or toxic metals, or breaks cells through mechanical rather than chemical effects, we'd be affected, and our immune system would have trouble dealing with them. Can we even build antibodies for opposite chiralities?
i'd hit it so hard, if you pulled me out you'd be the king of britain [bash.org]
When replicator molecules replicate, they make copies with the same handedness as themselves.
Is this necessarily true? If a left molecule replicates to the right molecule, which in turn replicates to a left molecule again, you'd probably end up homogenous organisms that could use any available molecules, left or right.
i'd hit it so hard, if you pulled me out you'd be the king of britain [bash.org]