116 HISTORY OF THE OCEANS 



important, perhaps the major, source of the carbon compounds on 

 which life was built. 



A study by Miiller (1953) on the nature of the carbonaceous 

 fraction of the meteorites extractable by organic solvents shows 

 that they are very complex and contain fractions of a bituminous 

 character — but different from terrestrial bitumen — which vola- 

 tilizes at temperatures between 100° and 300°C. This bitumen also 

 contained nitrogen, sulfur, and chlorine, the last in an organic 

 form. It would seem to take the form of a complex of an aromatic 

 polyacid, like humic acid, and iron. 



On the basis of these data it is possible to build a self-consistent 

 picture of the building up of planets from an original finely 

 dispersed meteoric dust formed at low temperatures. The compo- 

 sition of the mineral chlorite corresponds to the cosmic abundance 

 of the atoms of magnesium, silicon, and iron. Even more important 

 for the later developments is the presence of water in a form not 

 removable under 450°C. Minute paramagnetic flakes of chlorite a 

 few hundred angstroms in diameter and 15 angstroms thick, 

 magnetically oriented, may well be responsible for the polarization 

 of stellar light. In the outer zones of the solar system, such flakes 

 could serve as nuclei for a deposit of solid methane and ammonia 

 known to exist from Jupiter outwards. Now through the action 

 of cosmic rays or solar protons on this finely dispersed matter, it 

 seems likely that a certain degree of polymerization takes place to 

 form a bituminous layer surrounding the chlorite core. Some of 

 these bitumen-coated meteoritic flakes may then agglomerate into 

 snowball-like aggregates which would have a density of about 

 0.1 ^ 0.3. These in turn would weld into larger bodies until, with 

 a radius of some hundreds of kilometers, the center would be 

 crushed and highly heated by gravitational forces. This would 

 result primarily in the expulsion of volatile hydrocarbons and the 

 conversion of chlorite to olivine chondrites. Further heating in the 

 central part of such a body would give rise to a chemical reaction 

 between the residue of the bitumen and the iron-rich olivine, 

 resulting in the production of metallic iron which would separate 

 by gravity and leave an iron-poor silicate slag, such as is observed 

 in the iron meteorites and achondrite stony meteorites. At a 



