From dust astrophysics towards dust mineralogy-a historical review

Abstract

Via meteorite research, mineralogy became the first discipline among the earth sciences that developed a cosmic branch. The current link connecting astronomy and mineralogy is the dust in the Galaxy. Interstellar dust reached astrophysical topicality around 1930. In their first dust models astrophysicists took the assumption for granted that the grains consist of minerals related to those of the solar system. An exception formed the "ice" model prevailing in the decade 1950-1960. Scrutinizing discussions of the weak points of this model and new observations in the UV spectral range paved the way for considering refractory materials as grain constituents and stars and planetary systems as the main suppliers of such dust grains. In the decade 1960-1970 many refractory dust materials heuristically came into discussion, e.g. graphite and meteoritic silicates. The strong solid-state band detected at 217 nm in the interstellar extinction curves was commonly assigned to graphite grains. Beginning in 1968, observations of the vibrational bands of the SiO4 group in circumstellar as well as in interstellar dust provided ample evidence for the ubiquitous occurrence of silicate grains in the Galaxy. Bands of silicates and of some other solids opened the new era of dust diagnostics resting on IR spectroscopy and laboratory simulation experiments. In most cases, the observed spectral features indicated heavily distorted structures of the grain material. In 1996-1998 the Infrared Space Observatory (ISO) surprisingly discovered stardust bands of crystalline silicates. This opened the chance of unambiguously identifying dust minerals via astronomical spectroscopy in the combination with laboratory data of dust analogues. The term "astromineralogy" was coined. In the last two decades, mineralogists have discovered "fossil" dust grains in primitive meteorites, which had been preserved from the parent cloud of the solar system. This way, cosmic mineralogy could directly contribute to astrophysical dust research, and confirm astromineralogical conclusions. New ways of experimental research are on the horizon that could advance our understanding of interstellar dust. Promising results have been attained in detecting dust grains of the local interstellar medium that traverse the solar system. The interstellar meteors as messengers from other planetary systems could likewise become an important information source in the future. Intensified collaboration between astrophysicists and mineralogists should enclose discussions on the applicability of the traditional mineral definition on cosmic particulates and on a subdivision of the field of astromineralogy. © 2010 Springer Berlin Heidelberg.