Planetary Sciences American and Soviet Research/Proceedings from the U.S.-U.S.S.R. Workshop on Planetary Sciences (1991) / Chapter Skim
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5. Physical-Chemical Processes in a Protoplanetary Cloud
5. Physical-Chemical Processes in a Protoplanetary Cloud
Pages 61-69
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From page 61... ...
LAVRUKHINA V.I. Vernadskiy Institute of Geochemistry and Analytic Chemistry ABSTRACT According to current views, the protosun and protoplanetary disk were formed during the collapse of a fragment of the cold, dense molecular interstellar cloud and subsequent accretion of its matter to a disk.
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From page 63... ...
H2C~ Cycl~cal molecules Ions Radicals C3H2 SiC2X _-C`H CH+ HCO+ HCNH+ H3O+?
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From page 64... ...
One interesting feature pertaining to the distribution rates for certain interstellar molecules is their uniformity for dark molecular clouds with wide variation in P and T parameters. Furthermore, an inverse dependence of the amount of gas molecules on dust density is absent.
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From page 65... ...
PROPERTIES AND PlIYSICO-CHEMICAL PROCESS IN THE GENESIS OF INTERSTELLAR DUST GRAINS According to current thinking (Voshchinnikov 1986) , the total sum of molecules in a "dense," not-too-hot gaseous medium of complex molecular composition precipitates into a solid phase, thereby forming embryos of dust grains.
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From page 66... ...
liable 2 lists certain data on the characteristics of the basic physical and chemical processes involved in the formation and subsequent evolution of interstellar dust grains and the astrophysical objects in which these processes occur. With these data we can evaluate the nature of processes occurring in the protoplanetaty cloud during the collapse and subsequent evolution of the Sun.
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From page 67... ...
~ on gram sunace Formation of hydrides Low temperature Fe oxidation by monatomic oxygen FeO, Fe:O3, Fe3O4 T=2.5-5 K FeH, FeH:, hydrides of transitional metals Diffusion interstellar medium Daric GMC~, zones 6. Formation of envelopes and dust from solid organic compounds Radiation poly- Tolines, hexamethylentmerization of etramine, cellulose, organic complex organic or compounds with prebiological compounds T24K on grains (PAC)
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From page 68... ...
Ho oxygen components have been discovered in meteorites: impoverished and enriched i60 of nucleogenetic origin ~avrukhina 1980~. The relative abundance of oxygen isotopes in chondrules tells us that chondrite chondrules of all chemical groups are convergent in relation to a single oxygen reservoir, characterized by the values ~ t80 = 3.6 ~ 0.2L% and ~ 170 = 1.7 ~ 0.2L% (Lavrukhina 1987; Clayton e!
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From page 69... ...
1983. Oxygen isotopic compositions of chondrules in Allende and ordinary chondrites.
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