Exploring connections between near-earth objects and meteoroid streams

Ph.D. University of Hawaii at Manoa 2013.Includes bibliographical references.In this work we present a detailed investigation of the possible connections between near-Earth objects and meteoroid streams. In particular, we specifically explore the possibility that at least a fraction of the meteor showers observed on Earth originate from truly asteroidal parent bodies, where the formation and ejection of meteoric particles in the stream is caused by a process different from classical cometary outgassing. We first present the results of our search for possible progenitors of known meteor showers in the population of near-Earth asteroids, identifying a few dozen likely associations of streams with asteroidal bodies, and verifying the most promising ones with accurate dynamical ejection models. This list of possible linkages forms the basis for a specific observational effort, where we target a significant fraction of these proposed parent bodies with the goal of separating truly asteroidal ones from inactive cometary nuclei. The observations we collected allow us to identify at least a few truly asteroidal (rocky) objects embedded in well-established meteoroid streams. We also extend our observational investigation directly to the streams, attempting to detect them both in the optical wavelength range from the ground and in the thermal infrared via satellite observations. Although no large meteoroids or thermal signatures of streams could be detected, we are able to use the information to place meaningful constraints on the stream populations. Finally, we present the interesting and unexpected results of a detailed dynamical analysis of very small asteroids, in the size range of a few meters in diameter that directly compares with larger meteoroids. Our observations allow us to measure an unexpectedly low bulk density for most of these objects, which casts a new light on the possible role of asteroids as meteor stream progenitors, but also have very relevant implications for the field of impact hazard mitigation and future spacecraft exploration. We conclude our work with a summary of the information obtained from the various components of project, with a discussion of a possible coherent scenario capable of explaining the various results we obtained, and with possible future directions of this investigation