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There
are numerous theories regarding the origin of life. One recent theory is
that life originated from ice. This theory was first introduced by Stanley
Miller, a researcher with a lengthy publishing history on the subject of the
origin of life. He has written and co-written numerous peer-reviewed articles
concerning many theories about the origin of life, and wrote a book: The
Origins of Life on Earth. He is particularly well known for his involvement
in the Miller-Urey Experiment in 1953, one of the first experiments of
its kind, which simulated the hypothetical early Earth environment and
tested for chemical evolution. The idea that life may have originated from ice
is rather new and somewhat contradictory to many more common theories such as
those involving volcanic thermal vents, and so-called “primordial soup” in
tropical ponds.
Miller was confirmed to have synthesized complex organic polymers from
ammonia and cyanide keeping them at -108°F for approximately twenty-five
years. These results were published in the journal Icarus in June 2000 under
the title: Prebiotic synthesis of adenine and amino acids under Europa-like
conditions (Levy M, Miller SL, Brinton K,
Bada JL). A previous article
published in 1982 in the journal Biosystems, Prebiotic adenine
synthesis via HCN oligomerization in ice (Schwartz
AW, Joosten H, Voet AB), also investigates the production of adenine under
very cold conditions (-2°C), though it differs in its involvement with NH4OH.
A lot of research points to adenine as the first purine, though this idea is
still criticized occasionally (Shapiro R. 1995) These experiments seem to
better consider the likely environment on Earth when life began: a desolate
planet covered in a thick layer of ice (not unlike present day Europa).
Ice was not only probably what was most available on Earth at the time, it also
has certain properties that make it a likely vessel for the first prebiotic
molecules. All life requires liquid water, which is in abundance in more
conventional theories, and according to Douglas Fox, “small amounts of liquid
can persist even at –60°F. Microscopic pockets of water within the ice may have
gathered simple molecules like the ones Miller synthesized, assembling them
into longer and longer chains” ( Discover Magazine, 2008) Sea ice
has special qualities, research Hauke Trinks theorized that, “ice was doing
much more than just concentrating chemicals. The ice surface is a checkerboard
of positive and negative charges; he imagined those charges grabbing individual
nucleobases and stacking them … helping them coalesce into a chain of RNA.”
(Fox, 2008). According to Fox’s article, ice also may have a role in how small
RNA chains synthesized could have produced long chains that are seen in current
organisms. RNA enzymes act very differently when exposed to very cold
temperatures than they do at optimal temperatures. Primordial RNA may have
been encouraged to form longer chains because of their icy environment, in
which certain RNA enzymes have been shown to bind strands of RNA rather than to
cut them as they normally would at optimal temperatures (Vlassov, et.al. 2004).
Freeze/thaw cycles may also have allowed these prebiotic molecules to mix and
diversify in the ice, which may have resulted in certain RNA chains combining
and becoming various amino acids, leading to the first enzymes and
eventually, the first organisms.
While there are many theories about the origin of life all must be subject to
scrutiny and Miller’s ice theory is just one of many expanding theories. It and
all other current theories of life on earth may or may not be the correct
answers. As with many previous theories, it may make more sense to not look at
them as exclusive compartments, but rooms in a vast building in the
architecture of life exploring their combined possibilities.
Bibliography/ Works Cited:
Did Life Evolve In Ice? Fox, Douglas. Discover Magazine. 01 Feb. 2008.
Ice And The Origin Of Life. Trinks H, Schröder W, Biebricher C. Origins of Life and Evolution of the Biosphere. Vol. 35, No. 5, October 2005. pp. 429-445(17)
Ligation activity of fragmented ribozymes in frozen solution: implications for the RNA world. Vlassov AV, Johnston BH, Landweber LF, Kazakov SA. Nucleic Acids Research. 2004, Vol. 32, No. 9 2966-2974 © 2004 Oxford University Press
Prebiotic synthesis of adenine and amino acids under Europa-like conditions. Levy M, Miller SL, Brinton K, Bada JL. Icarus. 2000 Jun;145(2):609-13. Department of Chemistry, University of California, San Diego, La Jolla 92093-0506, USA.
Prebiotic adenine synthesis via HCN oligomerization in ice. Schwartz AW, Joosten H, Voet AB. Biosystems. 1982;15(3):191-3.
The prebiotic role of adenine: a critical analysis. Shapiro R. Orig Life Evol Biosph. 1995 Jun;25(1-3):83-98. Department of Chemistry, New York University 10003, USA
A Production of Amino Acids Under Possible Primitive Earth Conditions. Miller, Stanley L. Science 15 May 1953: Vol. 117. no. 3046, pp. 528 - 529
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