Dayhoff M O, Eck R V, Lippincott E R, Sagan C
Science. 1967 Feb 3;155(3762):556-8. doi: 10.1126/science.155.3762.556.
Because of the high temperatures prevailing in the lower atmosphere of Venus, its chemistry is dominated by the tendency toward thermodynamic equilibrium. From the atomic composition deduced spectroscopically, the thermodynamic equilibrium composition of the atmosphere of Venus is computed, and the following conclusions drawn. (i) There can be no free carbon, hydrocarbons, formaldehyde, or any other organic molecule present in more than trace amounts. (ii) The original atomic composition of the atmosphere must have included much larger quantities of hydrogen and a carbon/oxygen ratio </= 0.5. (This ratio is now almost precisely 0.5.) (iii) The present atomic proportions of the atmosphere of Venus are so unique that an evolutionary mechanism involving two independent processes seems necessary, as follows. Water, originally present in large quantities, has been photodissociated in the upper atmosphere, and the resulting atomic hydrogen has been lost in space. The resulting excess oxygen has been very effectively bound to the surface materials. (iv) There must be some weathering process, for example, violent wind erosion, to disturb and expose a sufficient quantity of reduced surface material to react with the oxygen produced by photodissociation.
由于金星低层大气中普遍存在高温，其化学性质受热力学平衡趋势主导。根据光谱推断出的原子组成，计算出金星大气的热力学平衡组成，并得出以下结论。（i）不可能存在超过痕量的游离碳、碳氢化合物、甲醛或任何其他有机分子。（ii）大气的原始原子组成必定包含大量更多的氢，且碳/氧比≤0.5。（目前该比例几乎恰好为0.5。）（iii）金星大气目前的原子比例非常独特，以至于似乎需要一个涉及两个独立过程的演化机制，如下所述。原本大量存在的水在上层大气中被光解，产生的原子氢散失到太空中。产生的多余氧气已非常有效地与表面物质结合。（iv）必定存在某种风化过程，例如剧烈的风蚀，以扰动并暴露足够数量的还原态表面物质，使其与光解产生的氧气发生反应。
