Interplanetary Dust Cloud

to understand its nature, origin, and relationship to Solar System s
(our own, as well as extrasolar systems).

The interplanetary dust Particles (IDPs) not only scatter solar light
(called the " Zodiacal Light ", which is confined to the
Ecliptic Plane ), the IDPs also produce Thermal Emission ,
which is the most prominent feature of the night-sky light
in the 5-50 micrometer wavelength domain (Levasseur-Regourd, A.C.
1996 ). The grains characterizing the infrared emission near the
Earth 's Orbit have typical sizes of 10-100 micrometers (Backman, D.,
1997 ). The total mass of the interplanetary dust cloud is about the
mass of an Asteroid of radius 15 km (with density of about 2.5
g/cm³).

The sources of IDPs include at least: asteroid collisions, Cometary
activity and collisions in the inner solar system, Kuiper Belt
collisions, and interstellar medium (ISM) grains (Backman, D., 1997). Indeed, one of the
longest-standing controversies debated in the interplanetary dust
community revolves around the relative contributions to the
interplanetary dust cloud from asteroid collisions and cometary
activity.

The main physical processes "affecting" (destruction or expulsion
mechanims) IDPs are: expulsion by Radiation pressure, inward
Poynting-Robertson (PR) Radiation Drag , Solar Wind pressure (with
significant electromagnetic effects), sublimation, mutual collisions,
and the dynamical effects of planets (Backman, D., 1997).

The lifetimes of these dust particles are very short compared to the
lifetime of the Solar System . If one finds grains around a star that is older
than about 10^8 years, then the grains must have been from recently
released fragments of larger objects, i.e. they cannot be leftover
grains from the protoplanetary Nebula (Backman, private
communication). Therefore, the grains would be "later-generation"
dust. The zodiacal dust in our solar sytem is 99.9% later-generation
dust and 0.1% intruding ISM dust. All primordial grains from the Solar System's formation have been removed long ago.

The interplanetary dust cloud has a complex structure (Reach, W.,
1997). Apart from a background density, this includes:

At least 8 Dust Trail s -- their source is thought to be

A number of Dust bands, the sources of which are thought to be Asteroid Families in the Main Asteroid Belt . The three strongest bands arise from the Themis Family , the Koronis Family , and the Eos Family . Other source families include the Maria , Eunomia , and possibly the Vesta and/or Hygiea families (Reach et al 1996).

at least 2 resonant dust rings are known (for example, the Earth-resonant dust

thought to have a resonant ring with a "wake") (Dermott, S.F.
et al., 1994, 1997)

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Interplanetary Dust Cloud