Proceedings IAU Symposium No. 236, pp. 107–120 (2007)
Properties of meteoroids from different classes of parent bodies
Jiri Borovicka
Astronomical Institute of the Academy of
Sciences, 251 65 Ondřejov, Czech Republic
Abstract. Meteoroids observed to disintegrate in the
terrestrial atmosphere can be directly linked to their parent bodies in
case that they belong to certain meteor showers. We present a list of
two dozens of parent bodies reliably associated with well recognized
meteor showers. Among the parent bodies are long period comets,
Halley-type comets, Jupiter family comets, comets of the inner solar
system (such as 2P/Encke) and asteroids. Physical and chemical
properties of meteoroids coming from various parents are compared on
the basis of meteor heights, decelerations, light curves and spectra.
Jupiter family comets produce meteoroids with the lowest strength,
namely porous aggregates of dust grains with bulk densities of about
0.3 g cm-3 or less. Halley type material is somewhat
stronger and the material related to comet Encke is even stronger. In
addition, small strong constituents, perhaps similar to carbonaceous
chondrites, can be encountered within the normal cometary material. The
strength of cometary material is also enhanced by long-term exposure to
cosmic rays and by solar heating in the vicinity to the Sun (r < 0.2
AU). Both these processes lead to the loss of volatile sodium. Southern
delta Aquariids, Geminids and partly also Quadrantids were influenced
by solar radiation. We argue that these showers, the asteroids
associated with them (3200 Phaethon and 2003 EH1), and the whole
interplanetary complexes they belong to are of cometary origin. The
argument is supported by lower than chondritic Fe/Mg ratio found in
Geminids as well as in Halley type comets. The typical property of
stony meteoroids of asteroidal origin is the presence of internal
cracks which cause that the incoming meteoroids are much weaker than
the recovered meteorites.
Keywords: meteors, meteoroids; comets: general;
asteroids
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