Interplanetary dust cloud

The interplanetary dust cloud has been studied for many years in order to understand its nature, origin, and relationship to solar systems (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). This article describes dust in the astronomical cosmic context, of which interplanetary dust and interstellar dust are particular types. ... The zodiacal light is a faint glow which appears in a band along the ecliptic or zodiac from the vicinity of the Sun. ... The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ...

The sources of IDPs include at least: asteroid collisions, cometary activity and collisions in the inner solar system, Kuiper Belt collisions, and 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 Sun. If one finds grains around a star that is older than 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, 0.1% intruding ISM dust, and 0% primodial grains from the Solar System's formation.

The interplanetary dust cloud has a complex structure (Reach, W., 1997). It has:

* at least 8 dust trails -- source is thought to be short-period comets, in particular the three asteroid families: Koronis, Eos, Themis,

* at least 2 resonant dust rings (the Earth resonant dust ring, for example, but every planet in our solar system is thought to have a resonant ring with a "wake", Dermott, S.F. et al., 1994, 1997)

References

Backman, Dana. (1997). "Exozody Workshop, NASA-Ames, October 23-25, 1997". Extrasolar Zodiacal Emission - NASA Study Panel Report, XX.

See: [[1]]

Dermott, S.F. Jayaraman, S., Xu, Y.L., Gustafson, A.A.S., Liou, J.C., (June 30, 1994). RA circumsolar ring of asteroid dust in resonant lock with the Earth. Nature 360: 79-?.

Dermott, S.F.. (1997). "Signatures of Planets in Zodiacal Light". Extrasolar Zodiacal Emission - NASA Study Panel Report, XX.

Levasseur-Regourd, A.C.. (1996). "Optical and Thermal Properties of Zodiacal Dust". Physics, Chemistry and Dynamics of Interplanetary Dust,ASP Conference series, Vol 104, 301-.

Reach, W.. (1997). "General Structure of the Zodiacal Dust Cloud". Extrasolar Zodiacal Emission - NASA Study Panel Report, XX.