Microanalytical Studies of Extraterrestrial Materials

Washington University, Saint Louis MO

Investigators

Abstract

EAR-9980394 Crozaz This proposal has two aspects that rely on the application of micro-analytical techniques we developed to study extraterrestrial materials. These techniques also have applications in geochemical studies of terrestrial samples. Part of our effort is directed to the study of presolar grains formed in the atmospheres of stars. They survived the formation of the solar system and are found in minute quantities in primitive meteorites. So far, we have made TEM/ion microprobe studies of the largest of these particles (> 1 micrometer) but will soon acquire a new type of ion microprobe - the NANOSIMS - which has unprecedented sensitivity and spatial resolution. This new equipment will allow us to make combined elemental and isotopic measurements at the 0.1 micrometer level, a size that better characterizes the majority of presolar grains and is ideal for TEM structural studies. It is expected that this work will advance our understanding of grain growth in various stellar atmospheres and of element formation in stars. It will also likely lead to the discovery of new presolar phases. A second major aspect of our work is the measurement of the microscopic distribution of minor and trace elements in petrographic thin sections of a variety of meteorite types to unravel their histories. Some of the meteorites are the results of asteroidal/planetary processes while others have components that formed in both nebular and asteroidal environments. Delineating these origins and the relationships between meteorites gives insights into the processes active in the early solar system, some 4.6 billion years ago.