

Detecting life on other planets by measuring molecular chirality - CatDancer
http://www.eurekalert.org/pub_releases/2009-04/nios-sga042309.php

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pavel_lishin
So, presence of oxygen and methane aren't necessarily indicators of life
because "that makes assumptions about what life is", but stating that life
must result in a huge majority of specific-handed molecules doesn't?

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jerf
You've got it backwards. They are not saying all life-bearing planets must
have chiral molecules, and therefore we can tell whether a planet has life
based on the light. They are saying that if a planet exhibits light coming
from a source with lots of chiral molecules, then the only known explanation
is life, and we can conclude it is life. A non-chiral source proves nothing
either way.

Note this same logic holds for oxygen. This expands our ability to positively
identify life to places that may not have gone the oxygen route. (We know this
is possible, because Earth itself was like that for a while, and we continue
to have a wide variety of anaerobic organisms, and even some complete
anaerobic biomes underground, I believe.) It does nothing to our ability to
negatively identify life (or positively identify lack of life, if you like),
which we have little ability to do in general.

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AndrewO
I'm wondering how likely this is to work over interstellar distances.
Especially, given most (if not all) extrasolar planets have been detected
through indirect means (see
[http://en.wikipedia.org/wiki/Extrasolar_planet#Detection_met...](http://en.wikipedia.org/wiki/Extrasolar_planet#Detection_methods))
rather than direct imaging.

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paraschopra
Though I haven't read the article, but if the title suggests that life is
limited to what we observe on Earth, then either we are defining life that way
(and by definition we would only have it on earth-like objects) or have taken
a very narrow view of what life is. Life is a very fuzzy concept, every
researcher, every journalist defines it in his own way. Does life have to have
carbon? Does it have to wiggle?

