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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."
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.
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.