Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt........53l&link_type=abstract
PhD Dissertation, Washington Univ. Seattle, WA United States
Astronomy and Astrophysics
Astronomy
Interplanetary Dust, Cosmology, Asteroids, Zodiacal Dust, Meteorite Collisions, Solar System, Particle Size Distribution, Atmospheric Entry, Aerodynamic Heating, Mass Distribution, Particle Acceleration, Meteoroid Concentration, Velocity Distribution, Temperature Effects, Infrared Astronomy Satellite, Gravitational Lenses, Focusing, Cometary Atmospheres, Asteroid Belts, Orbit Decay
Scientific paper
Interplanetary dust particles can provide a wealth of information about the history and environment of the solar system. Unfortunately, it has not yet been clear whether their parent objects were primarily asteroidal or cometary. This situation seriously limits the applicability of the information gained form dust studies. I present here five experiments intended to reveal the source of interplanetary dust. First, I examine the IRAS asteroidal dust bands to find the fraction of the zodiacal dust contributed by single asteroid sources. The bands studied here contain approximately 1% of the zodiacal emission, insufficient to assign parent objects to most of the material. Gravitational focussing effects may boost the dust band contribution in terrestrial IDP collections to as high as 15%. The second and third experiments address micrometeoroid collisions, which appear to forbid delivery of particles larger than about 10-5 g from the asteroid belt to the Earth, in turn implying a cometary or near-Earth source for large dust motes. I test the assumed meteoroid of realistic porous materials. The result is that the previous collisional model is essentially correct. The verified break in the slope of the meteoroid mass distribution is consistent with collisional removal of greater than 10-5 g particles on a timescale similar to their Poynting-Robertson orbit decay lifetimes, if most originate in the asteroid belt. The fourth and fifth experiments turn to atmospheric entry heating effects as velocity diagnostic to separate fast cometary particles from slower asteroidal ones. I develop a new, physically realistic numerical simulation of particle entry. This model provides general results on particle origins, but is most useful when coupled with accurate measurements (based on the release of solar wind implant helium) of the peak entry temperatures of individual particles. It is found that most particles enter at low speeds. The few high-temperature particles imply a cometary fraction near 20%. Taking these results together, and considering previous work such as the meteoroid velocity distribution, I find an asteroid:comet dust ratio of approximately 4:1.
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