>Found this relevant article at
http://www.space.com/scienceastronomy/astrobio_life_030415.html
>
TH
Interesting interview

 
>Interview with Carol Cleland
>Q: What is your opinion of attempts to define "life?"
>
>I argue that it is a mistake to try to define "life." Such
efforts reflect
>fundamental misunderstandings about the nature and power of definitions.
>
>
>Definitions tell us about the meanings of words in our language, as opposed
>to telling us about the nature of the world. In the case of life, scientists
>are interested in the nature of life; they are not interested in what the
>word "life" happens to mean in our language. What we really
need to focus
>on is coming up with an adequately general theory of living systems, as
>opposed to a definition of "life."

Th
I'll agree with this part.

>
>But in order to formulate a general theory of living systems, one needs
>more than a single example of life. As revealed by its remarkable biochemical
>and microbiological similarities, life on Earth has a common origin. Despite
>its amazing morphological diversity, terrestrial life represents only a
>single case. The key to formulating a general theory of living systems is
>to explore alternative possibilities for life. I am interested in formulating
>a strategy for searching for extraterrestrial life that allows one to push
>the boundaries of our Earth-centric concepts of life.

TH
I dont' think life has assorted boundaries -  I think as we learn more about
life we'll find it is very specific to a certain planet size, gravity,
atmosphere,  liquid water temp and mostly a heat cycle which MUST come first in
all cases 
One thing I have suggested is that SETI look in the spectrum near 260nm -
that's the UV light that nucleic acids aborb most. If life is similar than any
aliens will know all about 260 nm.


>Q: In the category of what is "alive," would you exclude what
you call the
>"borderline" cases - viruses, self-replicating proteins, or even
non-traditional
>objects that have some information content, reproduce, consume, and die
>(like computer programs, forest fires, etc.)?

TH
Def. are tricky for sure.

(snipped)

>
>Q: What is your favored theory for how life could have arisen on Earth -clay
>crystals, RNA world, membranes, or some other option?
>
>It seems to me that all theories of the origin of life face two major hurdles.
>The biggest one is explaining the origin of the complex cooperative schema
>worked out between proteins and nucleic acids -- the controlled production
>of self-replicating catalytic systems of biomolecules. 

TH

I don't think he's asking the right question here. The question we should ask
is how would proteins be more
stable hooked to nucleic acids, and how would nucleic acids be more stable in
their environment because of being hooked to proteins - the rest will come
later.

All of the popular
>accounts of the origin of life strike me as side stepping this issue. 

(snipped)

>But I still think that the more serious problem is the next stage of the
>process, the coordinating of proteins and RNA through a genetic code into
>a self-replicating catalytic system of molecules. 


TH
I think I have a major clue to this question. 
Purines were more stable than pyrimidines (because
of dimer damage only on pyrimidines)
AND
Hydrophilic amino acids were more stable than
hydrophobic because it was a watery environment.
Then - after answering the first question of why
proteins and nucleic acids were more stable together,
you can see that purines =hydrophilic and
pyrimidines - hydrophobic.

>I suppose that if I had to pick a favorite theory, it would be Freeman Dyson's
>double origin theory, which postulates an initial protein world that
eventually
>produced an RNA world as a by-product of an increasingly sophisticated
metabolism.

TH
Problem - what is powering all this?
Without the sun in the picture nothing makes sense
except fluke luck.

(snipped)
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 9/19/04 6:23:41 AM