166 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1935 



The formation of ammonia from its elements, in accordance with 

 the equation 



N2 + 3IL^2NH3 



liberates less energy. With excess of hydrogen, and at atmospheric 

 pressure, the amounts of nitrogen and ammonia should be equal 

 between 200° and 300° C. ; ammonia should predominate at lower 

 temperatures and at higher pressures. 



The oxides of nitrogen are endothermic and so would tend to 

 dissociate, rather than to form. 



We may now form a definite picture of the successive reactions 

 which will occur in the atmosphere of a cooling major planet. 

 At temperatures of about 1,000° the predominant hydrogen will 

 be mixed with steam, free nitrogen, and carbon dioxide; the carbon 

 monoxide which occurs in stellar atmospheres having long ago been 

 completely oxidized. With falling temperature the carbon dioxide 

 will be converted into methane before the water reaches its critical 

 temperature and begins to condense. After most of it has been 

 precipitated, the nitrogen will go over into ammonia. These re- 

 actions, however, will run their course at these relatively low tem- 

 peratures only with appropriate activation. For the formation of 

 methane an excellent catalyst is available in the partially reduced 

 oxides of iron which should be present on the rocky surface exposed 

 to hot hydrogen. These would be equally good for the ammonia, 

 but they may be at the bottom of the sea by the time the proper 

 temperature is reached. An adequate activation, however, would 

 be furnished by electrical discharges, and if terrestrial thunder- 

 storms are any guide, these should be abundant so long as vapors 

 arising from the hot ocean are being condensed. When the tem- 

 perature has fallen to that which the earth at present enjoys, there 

 will be an extensive atmosphere of hydrogen, mixed with the simple 

 hydrides — methane, ammonia, and water vapor — along with any inert 

 gases which may all along have been present, but with little or no 

 free nitrogen or carbon dioxide. Below this will be an ocean, per- 

 haps very deep, strongly alkaline with ammonia, and incidentally 

 containing in solution any compounds of sulphur and the halogens 

 which may originally have been present. The conditions in such 

 an alkalme ocean — its action on the rocky bed, the compounds which 

 it will hold in solution, and the deposits which it may form — would 

 be of great interest, but are outside our present scope. 



With further cooling the water will freeze, but at a temperature 

 below 0° C. depending on the percentage of ammonia. With one 

 part of the latter to two of water the freezing point would drop to 

 — 100° C, but it is doubtful if there is enough ammonia for this. 

 The major planets — even Jupiter — are still colder, and the water 



