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Table of Contents for Evolution On Trial |
"The
definitive proof concerning the extraterrestrial origin of these amino acids has to do
with their optical properties. More specifically, by optical properties, I mean the
direction in which a solution of such amino acids can rotate the plane of polarization of
polarized light that is passed through such a solution.
"On
Earth, when one shines polarized light through a solution of amino acids taken from a
biological or living source, then, in such a solution, all twenty of the amino acids which
form the proteins in Earth organisms will rotate, to the left, the plane of polarized
light shining through the solution. This is a distinctive signature of the amino acids of
Earth organisms.
"On the
other hand, if one throws together a batch of amino acids in the laboratory, one will end
up with what is called a racemic mixture. In other words, there will be equal numbers of
what are called, in accordance with an agreed upon convention, left- and right-handed
amino acids.
"This
means that if one were to shine polarized light through solutions made up of this racemic
mixture, one would find the direction of rotation of the plane of polarization shifting in
different ways. Sometimes the direction of rotation would be to the left, and sometimes
the shift in the plane of rotation would be to the right.
"When,
however, amino acids from these meteorites were placed in solution, they shifted the plane
of polarization exclusively to the right. This was entirely unlike what happens with
either the racemic mixtures of amino acids in the laboratory or the amino acid solutions
drawn from organisms on Earth.
"At
least two conclusions follow from this. First, the only explanation we have for the
origins of the amino acids in the Antarctic meteorites involves sources which are
extraterrestrial in nature. Secondly, the existence of such complex hydrocarbons suggests
that when conditions are right, whether on Earth or elsewhere, amino acids will arise
through natural processes.
"In
addition to amino acids, other kinds of complex compounds have been found in some
carbonaceous chondrites. One researcher, for instance, discovered hydrocarbon compounds
which appeared to have properties that could have played a role in membrane formation.
"This
same researcher also found a yellowish pigment-like material which was able to absorb
energy when light was shone on it. This pigment might have been some sort of precursor to,
or an early competitor of, the chlorophyll pigment system that eventually emerged in some
Earth organisms."
Professor
Yardley paused in his presentation to pour another glass of water. Once he filled the
glass, however, he did not drain the glass as he had done previously.
He held the
glass in his hand and took only occasional sips. After one of the sips, he said: "The
material strength of carbonaceous chondrite meteorites often is so low, many of them are
unable to traverse the Earth's atmosphere without undergoing an airburst phenomenon in
which they break up, and there is a release of many megatons of energy. Nonetheless, this
sort of disintegration results in an increased surface-area-to-volume ratio of the
remaining fragments which may allow some of the remnants to reach the ground with their
organic payloads still intact.
"Researchers,
in fact, have recovered fragments from catastrophic airbursts that are about a millimeter
in size. Those who have examined such fragments have observed no signs of heating in their
interiors and, therefore, any organic compounds which could have been there would have
been protected from the effects of both the explosion as well as the heat of friction from
passage through the Earth's atmosphere.
"Comets
have been hypothesized, by some researchers, to be another potential means of transporting
various kinds of hydrocarbons to Earth. These individuals have estimated, on the basis of
different methodological considerations, that the composition of comets may have a
hydrocarbon content which constitutes up to 14% of the mass of the comet.
"However,
certain kinds of disparities between, on the one hand, the cratering records of the
satellites of some of the outer-most planets, and, on the other hand, the cratering
records of the so-called terrestrial planets which are closer to the sun, have led some
scientists to maintain that very few comets are likely to have collided with Earth.
Considerable uncertainty surrounds the role, or lack of it, which comets may have played
in delivering organic molecules to Earth.
"There
are some scientists who have argued that a far more important method of bringing organic
compounds to the Earth may involve what are known as interplanetary dust particles. These
particles, which may be the remnants of comets or asteroid-asteroid collisions, are about
a micron in size, which is about one-thousandth of a millimeter.
"This
may seem excessively small, but one should keep in mind, many bacteria are no more than
one micron in diameter. Moreover, bacteria contain many, many, very complex hydrocarbon
molecules.
"Not
only are interplanetary dust particles big enough to contain, potentially, a variety of
complex hydrocarbons, some of these particles may have just the right kind of mass
properties which would prevent them from being incinerated by the frictional heat which is
generated during entry into the Earth's atmosphere. Some researchers have calculated that
those dust particles which are between 10-12 to 10-6 grams would be
decelerated sufficiently in our atmosphere to allow such particles, which have been
radiation-hardened by their trip through interplanetary space, to reach the surface
intact.
"If the
dust particles were smaller than this, they probably would be destroyed by the photolysis
which is brought about by the ultraviolet part of the spectrum of sunlight. If, on the
other hand, the dust particles were to approach the size of, say, small pebbles, they
would be destroyed by organic pyrolysis, or the decomposition brought about by the heat of
friction when traversing the Earth's atmosphere.
"Approximately
10% of an interplanetary dust particle's composition is in the form of hydrocarbon
molecules. In addition, the collective mass of the particles which enter our atmosphere is
estimated, by some, to outweigh many of the smaller, grapefruit-sized, meteorites by a
ratio of approximately 100,000 to 1.
"Some
researchers have calculated that carbonaceous chondrite meteorites and comets, when
considered together, could have transported as much as 1020 grams of organic
carbon, or hydrocarbons, to Earth during the prebiotic period which led to the
origin-of-life through natural chemical processes. If one adds this amount to that which
is believed to have come through interplanetary dust particles, one is talking about quite
a lot of organic carbon materials.
"Irrespective
of the precise extraterrestrial or exogenous source of the hydrocarbons, evolutionary
biologists believe these organic contents would have been released over time. Heavier,
water-soluble compounds, like amino acids, would have dissolved in the global ocean.
"Low-density
hydrocarbons, on the other hand, are likely to have become concentrated on the surface of
the ocean, much as an oil-slick does today. Eventually, these molecules, like so much
flotsam, would float on the tides to the shores of volcanic islands or continents in the
process of formation.
"The
same mechanism of tidal transportation, of course, also would occur in relation to the
heavier water-soluble compounds which went into solution in the ocean. The process
probably just would have taken longer."
Mr. Mayfield
was about to ask another question, when a man came through the door behind, and to the
left, of the judge. The man approached the judge and seemed to be relaying some message to
her in the form of a folded piece of paper.
Judge
Arnsberger took the paper silently and nodded her head in acknowledgement or thanks to the
man. She scanned the piece of paper briefly, and then put it down.
"Mr.
Mayfield," she said, "before you continue with your direct examination of this
witness, I'm afraid there is an urgent matter which awaits me in chambers. I ask for your
indulgence and extend my apologies, but I need to call a short recess of ten to fifteen
minutes."
Having made
her announcement, she banged her gavel. She quickly got up from her chair and soon
disappeared behind the door through which the messenger recently had come.
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