Margaret Oakley Dayhoff -- Thermodynamics of Planetary Atmospheres
| In the early 1960s, Dr. Dayhoff collaborated
with Ellis
Lippincott and Carl Sagan, among others, to develop thermodynamic models
of cosmo-chemical systems, including prebiological planetary atmospheres.
She used a computer to model atmospheric conditions and composition on various
planets under different conditions. To do this, she developed a computer
program that calculated equilibrium concentrations of gases in a planetary
atmosphere. The particular compounds and elements to be considered could
be chosen each time the program was run. The result was a highly versatile
program that could be used to model the background or average atmospheres
of Venus, Jupiter and Mars. In addition, it could model the present-day and
primordial terrestrial atmosphere. In her study of the primordial terrestrial atmosphere, Dr. Dayhoff showed that long -chain hydrocarbons (oils) would form naturally under reducing conditions. As the oxygen content of the atmosphere increased, a sharp cut-off point would be expected, after which such natural formation of oils would abruptly cease. The abundance of oil in the earth's crust may be explained in part by such formation of hydrocarbons before the oxygen content of the atmosphere passed the cut-off point. |
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| C-H-O
ternary diagram for the atmosphere of Mars. |
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Dr. Dayhoff was especially interested in whether a primordial atmosphere at thermodynamic equilibrium might have contained compounds necessary for the formation of life. She found that numerous small biologically important compounds can appear with no special equilibrium mechanism to explain their presence. On the other hand, there are compounds that are critical to life, such as ribose, adenine and cytosine, which are extremely scarce in the equilibrium situation. |
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