Astronomy and Astrophysics – Astrophysics
Scientific paper
Jul 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993metic..28r.454w&link_type=abstract
Meteoritics, vol. 28, no. 3, volume 28, page 454
Astronomy and Astrophysics
Astrophysics
Astrophysics, Cosmic Dust, Cosmic Rays, Interstellar Dust, Isotopes
Scientific paper
It has been my great privilege and pleasure to participate in the study of extraterrestrial materials during an exceptionally interesting scientific period. In this talk, I first intend to reminisce a bit. Partly, my goal is to communicate to younger members of the Meteoritical Society the sense of excitement that accompanied certain scientific developments that they now take for granted. Partly, I intend to use the occasion to point out some first- order problems that remain unsolved in several older areas of research. Following the treatment of matters past, I will finish by discussing the location and study of interstellar grains in situ in primitive meteorites--a subject of great current interest to me and several colleagues at the McDonnell Center for the Space Sciences at Washington University. By and large, my work has not dealt with the formation of various types of extraterrestrial materials per se; rather, I have used extraterrestrial samples to learn about other aspects of the history of the solar system. My start in our field came from the thought, later realized in practice, that energetic, heavy nuclear particles might produce tracks in lunar rocks making them the equivalent of nuclear emulsions in recording galactic and solar radiations impinging on the lunar surface. The development of fission track dating and the discovery of excess fission tracks from the decay of 244Pu were outgrowths of that work. Similarly, the work on Brownlee particles (IDPs) was primarily motivated by the idea that some of the particles were probably from comets and that comets were a good place to look for interstellar grains. The desire to study IDPs stimulated the development of a number of microanalytic techniques including, notably, ion microprobe measurements of isotopes in small samples. This led, in turn, in our laboratory, to the identification of individual interstellar grains of SiC and graphite in acid residues prepared at the University of Chicago. The study of interstellar grains is an entirely new field of astrophysics that represents an increasingly important part of contemporary meteorite research. The location and study of interstellar grains in situ is accomplished using an X-ray mapping technique. By optimizing the mapping parameters in our EDS system, it is now possible for us to locate one interstellar grain every day or so in favorable cases. Several dozen SiC grains have been found in situ and typical examples will be shown. One of the ultimate goals of this work is to remove and study the surface properties of interstellar grains that have not been subjected to the harsh chemical treatments used to produce acid residues. Progress towards this goal will be reviewed at the meeting. The work I describe is a shared enterprise with many others and this is a great part of the joy derived from it. The capacity of science to transcend national boundaries, cut across cultural differences, and even to span age differences, is a source of continuing amazement and pleasure in a world otherwise much taken with conflict.
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