Blunderov
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"We think in generalities, we live in details"
  
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RE: virus:'Goodbye Mars, Hello Earth'
« on: 2005-04-10 08:23:29 » |
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[Blunderov] Interesting man, Paul Davies.
http://aca.mq.edu.au/PaulDavies/pdavies.html
He is, I think, one of those rare upper echelon scientists who believe
in god. Worth pointing out is that in spite of this he does not seem to
feel compelled to deny evolution.
Best Regards.
<q>
Goodbye Mars, Hello Earth
By PAUL DAVIES
Published: April 10, 2005
http://www.nytimes.com/2005/04/10/opinion/10davies.html?th&emc=th&oref=l
ogin
Sydney
WHEN I was a student in the 1960's, anyone who believed that there might
be life on other planets was considered a crackpot. Now all that has
changed. To claim that life is widespread in the universe is not only
respectable, it also underpins NASA's ambitious astrobiology program.
Find another Earth-like planet, astrobiologists say, and life should
have happened there too.
NASA is spending billions of dollars to search for life on Mars, the
most Earth-like of our sister planets. But we may not need to go all the
way to Mars to find another sample of life. It could be lurking under
our very noses. No planet is more Earth-like than Earth itself, so if
life started here once, it could actually have started many times over.
Geologists believe life established itself on Earth about four billion
years ago. Australian rocks dated at 3.5 billion years contain
fossilized traces suggesting that microbes were already well ensconced
by then. But the ancient Earth was no Garden of Eden. Huge asteroids and
comets mercilessly pounded the planet, creating conditions more
reminiscent of hell. The biggest impacts would have swathed our globe in
incandescent rock vapor, boiling the oceans dry and sterilizing the
surface worldwide.
How did life emerge amid this mayhem? Quite probably it was a
stop-and-go affair, with life first forming during a lull in the
bombardment, only to be annihilated by the next big impact. Then the
process was repeated, over and over. As the bombardment began to abate
and the impacts diminished in severity, so isolated colonies of
primitive microbes sheltering deep underground managed to cling on. One
of these colonies was destined to become life as we know it.
What about the preceding life forms? Were they all completely destroyed?
It's possible that pockets of microbes could have survived in obscure
niches until the next genesis, opening up the tantalizing prospect of
two or more different forms of life co-existing on the same planet.
Although they would compete for resources, one type of life is not
necessarily bound to eliminate the rest. After all, within the microbial
realm of "life as we know it," many different species make a living side
by side.
Thus, microbes from another genesis - alien bugs, if you will - could
conceivably have survived on Earth until today. The chances are that we
wouldn't have noticed. Under a microscope, many microbes appear similar
even if they are as genetically distinct as humans are from starfish. So
you probably couldn't tell just by looking whether a micro-organism is
"our" life or alien life. Genetic sequencing is used to position unknown
microbes on the tree of life, but this technique employs known
biochemistry. It wouldn't work for organisms on a different tree using
different biochemical machinery. If such organisms exist, they would be
eliminated from the analysis and ignored. Our planet could be seething
with alien bugs without anyone suspecting it.
How could we go about identifying "life as we don't know it"? One idea
is to look in exotic environments. The range of conditions in which life
can thrive has been enormously extended in recent years, with the
discovery of microbes dwelling near scalding volcanic vents, in
radioactive pools and in pitch darkness far underground. Yet there will
be limits beyond which our form of life cannot survive; for example,
temperatures above about 270 degrees Fahrenheit. If anything is found
living in even harsher environments, we could scrutinize its innards to
see whether what makes it tick is so novel that it cannot have evolved
from known life.
Identifying alien organisms in more equable settings would be a much
harder challenge, especially if they use the same basic molecules as
familiar life - nucleic acids and proteins. But there is one sure-fire
giveaway. The building blocks of proteins, called amino acids, are all
lopsided in the same distinctive way. Viewed in a mirror, these
"left-handed" amino acids would appear right-handed. Such mirror-image
molecules exist, but the life forms we are familiar with don't use them.
Most biochemists think it is just an accident that "life as we know it"
selected the left-handed version. If this supposition is correct, then
there is a 50-50 chance that alien life would have picked the opposite
handedness. Such "anti-life" would eat "anti-food": right-handed amino
acids and other mirror molecules. This offers a simple way to filter out
known life from anything alien. Prepare a culture medium of anti-food
and see if anything flourishes. Of course it's a long shot, but it is
easy to try, and scientists at the Marshall Space Flight Center are now
testing the response of microbes from various extreme environments to a
bowl of anti-soup.
Even if alien life has not endured to the present day, it may still have
left its mark. Geochemists have identified organic detritus from ancient
microbes in rocks as old as 2.7 billion years. Alien organisms might
have left remnants containing peculiar suites of molecules or produced
distinctive geochemical alterations like unusual mineral deposits.
These remnants would still give us a genuine second sample, a form of
biology that is unrelated to familiar life. By comparing the way
evolution works in both cases, we could identify which features of life
follow from general principles and which are just accidents of history.
But there is a more profound dimension to this research. Nobody knows
how life began. Somehow a mixture of lifeless chemicals assembled itself
into a primitive organism, presumably through a long and complex
sequence of chemical reactions. Our ignorance of this process is so
great that scientists can't even agree on whether it was a gigantic,
one-time fluke, or the expected and frequent outcome of intrinsically
bio-friendly natural laws, as the astrobiologists hope. Jacques Monod, a
Nobel Prize-winning biologist, was adamant that life is a bizarre
accident confined to Earth. On the other hand Christian de Duve, another
Nobel laureate, declares life to be "a cosmic imperative," bound to
occur wherever Earth-like conditions prevail.
The discovery of a second sample of life on Earth would confirm that
bio-genesis was not a unique event and bolster the belief that life is
written into the laws of the cosmos. It is hard to imagine a more
significant scientific discovery. Our view of the universe and our place
within it would be forever transformed, and we would at last have the
answer to the biggest of the big questions of existence: Are we alone?
Paul Davies, a professor at the Australian Center for Astrobiology at
Macquarie University, is the author of "The Fifth Miracle: The Search
for the Origin and Meaning of Life<q>
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