Mineralogical survey of near-Earth asteroid population: Implications for impact hazard assessment and sustainability of life on Earth.

摘要

Catastrophic events have channeled the course of evolution of life on planet Earth. Giant asteroidal and cometary impacts in the geologic past are known to have caused some of the great mass extinctions. Impacts by near-Earth asteroids (NEAs) are the only natural threat that can lead to the extinction of the human race. It is also the only threat which can be prevented if the object can be detected with sufficient lead time. Near-IR spectroscopy provides us with the opportunity to determine the composition of asteroids via mineral absorption features and analyzing them using laboratory mineral and meteorite spectra.Research work done as part of this dissertation comprises of two parts, a) telescopic spectral studies of asteroids, and b) development of laboratory mineral spectral calibration to interpret telescopic data. All telescopic data was obtained using the NASA HUT on Mauna Kea, Hawaii and the laboratory spectra from HOSER lab at the University of Winnipeg. Manitoba, Canada. Telescopic data were processed using IRAF and SpecPR software and all band parameters (telescopic and lab data) were derived using SpecPR.Three research projects were accomplished using telescopic spectral observations. The first is the study of S-type silicate-rich NEAs which suggests that S(IV) type asteroids are more abundant than other subtypes. The second is the determination of albedo and diameter of NEAs using thermal excess beyond 2.0 mum. The diameter estimated using this method are +/-10% of those estimated by radar. The final and probably the most important study is the link between Baptistina Asteroid Family and K-T impactor (dinosaur extinction event 65 million years ago) proposed by Bottke et al. (2007). Work done as part of this study proves that there is no link between Baptistina and K-T impactor based on their composition.Laboratory mixtures of ortho- and clinopyroxenes suggest a complex relationship between band parameters and mineral abundance. This study shows that there is no simple mechanism for estimating the abundance of ortho- and clinopyroxenes in a mixture using spectral band parameters. Spectral mixtures of orthopyroxene and Type A clinopyroxene were also studied and compared to orthopyroxene and olivine mixtures.