[extropy-chat] ET is a Bacterium

[The Avantguardian]

--- Amara Graps <amara at amara.com> wrote:

> >      That bacteria could survive long enough in
> space
> >to colonize other worlds is pretty well documented.
> 
> millions of years ? (the traveling time in space of
> the Martian
> meteorites span years to millions of years).

Yes but we KNOW that spores at least 10,000 years old
have been revived. And we have more controversial
reports of spores estimated 25 to 40 million years old
being revived.

> There is a large range of conditions to test for
> these three
> steps. Many aspects look feasible, but results are
> along ways
> away to support your first sentence.

In the context of empirical proof, I agree with you
that I may have over-stated the documentation to
support my claim. But I am looking at it from a more
holistic POV. If one considers the three major origin
theories that are currently out there and evidence for
and against them, I think statistical weight falls
squarely behind Pan-spermia:

1. Spontaneous Generation: All the various thories of
the chemical evolution of life on earth from "scratch"
including but not limited to Watson's RNA world. The
only real evidence for this is that RNA is capable of
enzymatic self modification. There is also some
resemblance of certain clay/water colloids to cell
membranes. The evidence against this is that it has
not been demonstrated to occur anywhere, in nature or
in the lab where pre-biotic conditions can be
simulated. In fact the spontaneous generation of life
was specifically disproven by Louis Pasteur and other
19th century biologists. After over 200 years of
progress of biological study, one thing that
biologists are certain of is that all existing life
came from pre-existent life.   

2. Intelligent Design: You all know and the arguments
for this, and, I am pretty sure, likewise think they
are bogus.

3. Panspermia: Aside from experimental evidence for
this (bacterial spore experiments in space) and the
lack of negative evidence refuting it, there are
Bayesian arguments for it. The endospore is very
obviously an evolved trait of many bacterial species
some of which are extremophiles. Adaptations in nature
are normally guided by selective pressures and do not
tend toward overkill. That is to say that gazelle
evolved the ability to outrun lions and cheetahs but
they cannot outrun race-cars because there was no need
for them to evolve to be THAT fast. But in endospore
forming bacilli, we have bacteria that evolved high
degrees of resistance to vacuum, temperature extremes,
gamma rays, and other forms of ionizing radiation. If
they WERE terrestrial in origin, what possible
selective pressure would there be for them to develop
vaccuum resistance and gamma radiation resistance? 

     Many species of life on earth form dormant spores
and cysts that allow them to survive conditions of
drought and scarcity of nutients but none of these
other creatures can survive vaccuum and hard
radiation. Why are bacilli special in this regard? If
you were to find some artificial construction with the
structural integrity, shielding, and enviromental
systems capable of supporting life in space, why would
you assume it was someone's house and not a space
capsule? Why would any engineer design something
capabable of withstanding the rigors of outer-space if
that something was not in fact meant to go into space?
If it looks like a duck and quacks like a duck. . .

      The other argument is one based on the behavior
of low frequency events. Since, we have never observed
it in nature or the laboratory, spontaneous generation
is by definition a very low probability event. To
assume therefore that it initially occured here on the
third rock of sol when the entire galaxy is a
potential sample space is silly. None of the elements
and compounds in the earth are unique or special, they
occur through out the universe. The only thing that is
special about the earth is their proportions here are
suitable for life. Statistically it would stand to
reason that with something like 10^11 trials (stars)
over some 15 billion years, there should be MANY
worlds within a range of conditions suitable for life.
If you lived in a town with a population of only a few
hundred and you saw a photograph of siamese twins but
you didn't know where the picture was taken, you would
be safest in assuming that they were NOT born in your
town. This is simply the result of the fact that, even
if you do not know the exact frequency at which
siamese twins are born over all, you know that they
are very rare and the population differential between
your town and the rest of the world is so large.
     Microbes are by the far the big winners of the
evolution game. For all our genius we could not
eradicate the microbes of the world if we tried. They
have evolved to exist in all kinds of environments
from deep sea to arctic to volcanic vents in the
earth's crust. Why is it so hard to believe that a
family of microbes could have evolved the ability to
survive space travel when this would be such a useful
adaptation to have?  

> See the chapter: Viable Transfer of Microorganisms
> in the Solar System
> and Beyond by Gerda Horneck, et al. in
> _Astrobiology: The Quest for
> the Conditions of Life_ by Springer 2002.
> 
> It is an extremely comprehensive report, detailing
> the conditions that
> they have tested bacteria and the conditions that
> they still need to
> test.

Thanks for the tip, I will try to find a copy when I
get a chance. 

Ciaou,


The Avantguardian 
is 
Stuart LaForge
alt email: stuart"AT"ucla.edu

"The surest sign of intelligent life in the universe is that they haven't attempted to contact us." 
-Bill Watterson

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