by the other planets and satellites whose compositions we come 

 more and more to know. The meteors, too, offer samples stored in 

 the refrigerator of orbit by which we try to conclude what material 

 made up the Earth. We are pretty sure that there was plenty of time, 

 for the orbital processes are speedy compared to most geological 

 ones. Free fall is faster than the drift of continents and the weather- 

 ing of mountains to fill the seas with silt. Even such grand geological 

 dramas take a fifth of a billion years at most. So there is ample time; 

 the physical processes were more or less over and became familiar 

 within a couple of hundred million years (m.y.) or so. But what that 

 earliest stable Earth was like is a question still beyond the grasp of 

 our models; the biologists look to the planetary sciences for the 

 initial conditions of sea and air, and the physical studies still seek a 

 constraining hint from what the biochemists will tell them of the 

 initial atmosphere! 



There has been one unexpected finding in space within the 

 last decade especially. It is the universal prevalence of carbon- 

 containing molecules. The linked atoms of carbon were once thought 

 to be solely the work of life. Now we find them overall, in plenty. 

 A substance like ethyl alcohol exists in vast quantities, though 

 gaseous and dilute to the point of vacuum, spread in the huge, thin 

 clouds of interstellar gas. Substances of even more complex and life- 

 like kind are found in the meteorites that fall now and again to 

 Earth, some of which resemble a blackened cheese, soft and 

 carbon-rich in substance. These are certainly products of the evolu- 

 tion of the meteorites, perhaps somewhat associated with the debris 

 of minor planets or at least with the conditions of the solar nebula 

 where the planets grew. There is a chance that these carbon com- 

 pounds may have contributed such useful organic resources directly 

 to the early Earth, which was certainly heavily bombarded with gifts 

 from orbit. Most workers believe that the surface of the Earth itself 

 was fully suited for the production of organic carbon compounds 

 from the commonplace atoms, like carbon and hydrogen, which were 

 already in place. It is the density which must be of importance, for 

 complex molecules arise out of the close proximity of several atoms 

 leading to their eventual union, an event none too common within 

 the dilution of space. Exactly that condition (the temperature, too, 

 must be permissive) gives our Earth its liquid water, intimately, indis- 

 pensably part of life, ancient and modern. Perhaps no other place we 



