Life is a continuum of chemical interactions, substantive responses that trigger more chemical interactions until the emergent phenomena of life are no longer sustained, and death of the living being occurs. At death, the whole may seem to be present, but the emergence called life is gone.
Life depends on continuous interrelated chemical reactions. It stops when energy exchanges cannot operate.
It seems reasonable to assume that the beginnings of life on Earth were also a continuum of chemical reactions, exchanging energy in a sustainable way to build on whatever was available in the environment.
The alkaline hydrothermal vents, discussed in previous blogs, are being studied as such an environment.
For life to continue and take advantage of new opportunities, it must out-compete other life. It makes simple sense that the most flexible and stable and reactive materials will make organisms that can win the race for food, safety, and energy. We Earthlings are made of those substances—including the talented element carbon and the ubiquitous solvent water—so its most likely that life anywhere will make use of those substances (if they are available) and will probably win the survival race.
The list of possibilities for finding life elsewhere expands as we continue to learn about the remarkable talents of various chemicals. A recent finding reported in January 2 Angewandte Chemie suggests that carbon—our favorite building block for life—is even more versatile than thought. It usually shares four electrons to bond with other atoms, but hexamethylbenzene has been found to be stable in strong acid when it reinvents itself as a five-sided pyramid. One carbon atom sits on top, bonded to five (instead of four) in a ring below and one above. Leave it to carbon to perform such gymnastics. This finding strengthens the idea of carbon being the most likely element able to come up with structures and flexibility demanded by life’s rigorous demands in challenging environments.
Another hopeful finding involves enzymes. Science Magazine of December 22 reports on evolutionary changes in the enzyme adenylate kinase, a protein found in “nearly all life forms.” This ancient enzyme may have been designed to work well in ancient hot climates, warm hydrothermal vents or hot springs. As Earth cooled, the “genes accumulated mutations” that changed some amino acids and lowered the enzyme’s energy demands.
Instead of expected instability, the adenylate kinase enzyme was found to work fast at “low temperatures while remaining stable at high temperatures.” Such “generalist enzymes” doing their job over a wide range of temperatures bode well for finding life in various environments.
In the article “Organic Aerosols and the Origin of Life: An Hypothesis” (by D. J. Donaldson, Tervahattu, Tuck and Vaida) aerosols of palmitic, stearic and oleic acids were said to be “energetically capable of asymmetric division.” In a “prebiotic terrestrial environment,” the products of their fission would have been the size of bacteria or viruses. The authors suggest that recent palaeo fossil studies could add to the understanding of possible biochemical interactions coming from the geochemistry involved.
The bottom line: We are still learning biochemistry at every level, and though we appreciate the intricacy of requirements for starting life, they may someday be within our understanding.
Author of The Archives of Varok
The View Beyond Earth (Book 1.)
The Webs of Varok (Book 2.)
Nautilus Silver Award 2013 YA
ForeWord IBPA finalist 2012 adult SF
The Alien Effect (Book 3.)
An Alien’s Quest (Book 4. Released Nov.21, 2016)
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