炭素質コンドライトは本当に未分化な物質か

抄録

The carbonaceous chondrites are the most primitive surviving materials from the early solar system, and thus they may provide important information regarding the early processes in the solar system. Some carbonaceous chondrites, CI and CM types in particular, consist in large part of fine-grained phyllosilicates, which account for most of the water in the meteorites (5-20 wt.% H₂0). Previous studies suggested that the phyllosilicates were formed by aqueous alteration on the meteorite parent body, but formation by direct condensation from the solar nebula has not been ruled out. This paper reviews, in the first part, results of mineralogical and chemical studies indicating the primitive nature of the carbonaceous chondrites, and reviews, in the second part, studies dealing with aqueous alteration experienced by these meteorites. This paper also discusses important points of information and their implications regarding the carbonaceous chondrite parent body.