It has been long understood that in the early history of the
earth before the appearance of life, there were present organic substances that
were the precursors to the complex compounds that are the essential ingredients
for all living things. These molecular
precursors are referred to as prebiotic organic matter. In addition, the cosmological data has
established that the earth along with all the other planetary bodies within our
solar system were formed from material expelled from the sun during its formation
– the so-called “protoplanetary disk.”
A fundamental question that arises from these known
occurrences is the actual origin of prebiotic organic matter. One of the possible answers to this question
is that these materials may have been seeded as a result of collisions of
meteorites on the earth’s surface. This
postulate is made even more plausible if one takes into account the fact that
in the early history of the planet collisions with meteorites were exceeding
common.
Of particular interest is a class of meteorites referred to
as the carbonaceous chondrite meteors that are believed to be samples of
primitive meteorites that contain the material that was part of the formation
of planet earth some 4.6 billion years ago.
These generally consist of insoluble organic matter (IOM) and soluble
organic matter ((SOM).
Dr. Christopher D. K. Herd from the Department of Earth and
Atmospheric Sciences at the University of Albert, Canada and his colleagues
systematically analyzed the Tagish Lake – in the Southwest region of the Yukon
in Canada - meteorite specimens that fell on the frozen lake and were harvested
within a few days. The freshness of the
samples effectively ruled out the possibility of contamination from the local
environment – an issue that is always of major concern in these types of
studies. The investigative group chose
four samples for detailed evaluation.
Their findings were of extreme interest, for they discovered
that the water extracts from these samples were dominated by monocarboxylic
acids (MCAs) including formic and acetic acids that play key and ubiquitous roles
in the biochemical metabolism of life on the planet. They isolated eleven different examples of
this class of organic compound. In
addition to these, amino acids were also identified. Amino acids are the basic building blocks
from which all proteins are constructed.
The evidence that was accumulated in these studies supports an
extraterrestrial origin for these compounds.
This conclusion, if true, is of immense value in understanding
the evolution of life on planet earth as well as encouraging speculation as to
the possibility of life on other worlds or so-called “exoplanets.”
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