The Role of Presolar Dust in the Formation

of the Solar System

by Gary Robert Huss

Under the supervision of Professor Robert Gehrz

ABSTRACT

Paradigms play an important role in directing scientific research and in interpreting scientific data. Over the last fifteen years, a large body of data has been gathered that is at odds with standard paradigms that underlie research on meteorites and the origin of the solar system. This thesis is an attempt to construct an interpretive framework encompassing all of the apparently contradictory data on meteorites and other solar system objects. The most important single difference between this new theoretical framework and the one that is presently popular is the explicit elimination of the assumption that the majority of the solids that make up the meteorites and terrestrial planets formed by condensation from a hot, gaseous, solar nebula. This assumption requires that the pre-existing interstellar dust evaporated during the formation of the solar system, but a growing body of isotropic data on components from primitive meteorites indicates that a considerable fraction of this presolar dust survived. The thrust of this thesis is that the primary building material for meteorites and terrestrial planets was presolar dust which survived evaporation during the formation of the solar system.
 
The first two chapters of the thesis introduce the problem and present a history of the thought that led to the paradigm that is now popular. Chapters 3-5 discuss the presently available data on interstellar dust; the conditions in interstellar space; star formation; chondritic meteorites and their potential as sources of information about the formation of the solar system; and the chemical , mineralogic, and isotropic data that has been acquired from chondritic meteorites. Chapter 6 sketches the broad outlines of a model that seems to explain the chemical , isotropic and textural information from meteorites in terms of the ability of various kinds of interstellar dust to survive the formation of the sun. Chapter 7 describes an attempt to model numerically the chemical processing believed to have taken place in the accretion disk, and discusses the implications of the results of that calculation. Chapter 8 summarizes several potential avenues of additional work that can be undertaken to both improve the scope of the model and to test the general approach.