Interplanetary dust cloud 2472666 221252413 2008-06-23T18:45:33Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{Cleanup|date=January 2008}} The '''interplanetary dust cloud''' has been studied for many years in order to understand its nature, origin, and relationship to [[planetary system]]s (our own, as well as extrasolar systems). The [[Cosmic dust|interplanetary dust particles (IDPs)]] not only scatter solar light (called the "[[zodiacal light]]", which is confined to the [[ecliptic|ecliptic plane]]), the IDPs also produce [[thermal]] [[Emission (electromagnetic radiation)|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/cm<sup>3</sup>). The sources of IDPs include at least: asteroid collisions, [[comet|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 mechanisms) IDPs are: expulsion by [[radiation pressure]], inward [[Poynting-Robertson drag|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 disk]] (Backman, private communication). Therefore, the grains would be "later-generation" dust. The zodiacal dust in the solar system is 99.9% later-generation dust and 0.1% intruding ISM dust. All primordial grains from the Solar System's formation were 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 short-period comets. * A number of dust bands, the sources of which are thought to be [[asteroid family|asteroid families]] in the [[main belt|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 family|Maria]], [[Eunomia fmily|Eunomia]], and possibly the [[Vesta family|Vesta]] and/or [[Hygiea family|Hygiea]] families (Reach et al 1996). * at least 2 resonant dust rings are known (for example, the Earth-resonant dust ring, although every planet in the solar system is thought to have a resonant ring with a "wake") (Jackson and Zook, 1988, 1992) ,(Dermott, S.F. et al., 1994, 1997) ==Collecting interplanetary dust on earth== In 1951, Fred Whipple predicted that micrometeorites smaller than 100 micrometers in diameter might be decelerated on impact with the earth's upper atmosphere without melting<ref>F. L. Whipple (1950) The theory of micrometeorites, part I: In an isothermal atmosphere, ''Proc. Nat. Acad. Sci.'' '''36''':687-695</ref>. The modern era of laboratory study of these particles began with the stratospheric collection flights of Brownlee and collaborators in the 1970's using balloons and then U2 aircraft<ref>D. E. Brownlee (1978) Interplanetary dust: Possible implications for comets and presolar interstellar grains, in ''Protostars and Planets'' (ed. T. Gehrels, U. Arizona Press, Tucson) pp. 134-150</ref>. Although some of the particles found were similar to the material in present day meteorite collections, the nanoporous nature and unequilibrated cosmic-average composition of other particles suggested that they began as fine-grained aggregates of nonvolatile building blocks and cometary ice<ref>P. Fraundorf, D. E. Brownlee, and R. M. Walker (1982) Laboratory studies of interplanetary dust, in ''Comets'' (ed. L. Wilkening, U. Arizona Press, Tucson) pp. 383-409.</ref>. The interplanetary nature of these particles was later verified by noble gas<ref>B. Hudson, G. J. Flynn, P. Fraundorf, C. M. Hohenberg, and J. Shirck (1981) Noble gases in stratospheric dust: Confirmation of extraterrestrial origin, ''Science'' '''211''':383-386.</ref> and solar flare track<ref>J. P. Bradley, D. E. Brownlee and P. Fraundorf (1984) Discovery of nuclear tracks in interplanetary dust, ''Science'' '''226''':1432-1434.</ref> observations. In that context a program for atmospheric collection, and curation, of these particles was developed at [http://curator.jsc.nasa.gov/dust/ Johnson Space Center] in Texas. This stratospheric micrometeorite collection, along with [[presolar grains]] from meteorites, are unique sources of [[extraterrestrial_materials|extraterrestrial material]] (not to mention being small astronomical objects in their own right) available for study in laboratories today. ==See Also== *[[Cosmic dust]] *[[Micrometeoroid]] *[[Atmospheric entry]] ==References== {{cite journal | author=Jackson A.A.; Zook, H.A. | title=A Solar System Dust Ring with the Earth as its Shepherd | journal=Nature| year=1988 | volume=337 | pages= 629 | doi=10.1038/337629a0}} {{cite journal | author=Jackson A.A.; Zook, H.A. | title=Orbital evolution of dust particles from comets and asteroids | journal=Icarus| year=1992 | volume= 97 | pages= 70–84 | doi=10.1016/0019-1035(92)90057-E}} {{cite conference | author=Backman, Dana | title=Exozody Workshop, NASA-Ames, October 23-25, 1997 | booktitle=Extrasolar Zodiacal Emission - NASA Study Panel Report | year=1997 | pages=}} See: [http://astrobiology.arc.nasa.gov/workshops/zodiac/backman/backman.txt NASA Panel Report on Extrasolar Zodiacal Emission] {{cite journal | author=Dermott, S.F. Jayaraman, S., Xu, Y.L., Gustafson, A.A.S., Liou, J.C., | title=RA circumsolar ring of asteroid dust in resonant lock with the Earth | journal=Nature| year=June 30, 1994 | volume=360 | pages=79-?}} {{cite conference | author=Dermott, S.F. | title=Signatures of Planets in Zodiacal Light | booktitle=Extrasolar Zodiacal Emission - NASA Study Panel Report | year=1997 | pages=}} {{cite conference | author=Levasseur-Regourd, A.C. | title=Optical and Thermal Properties of Zodiacal Dust | booktitle=Physics, Chemistry and Dynamics of Interplanetary Dust, ASP Conference series, Vol 104 | year=1996 | pages=301-}} {{cite conference | author=Reach, W. | title=General Structure of the Zodiacal Dust Cloud | booktitle=Extrasolar Zodiacal Emission - NASA Study Panel Report | year=1997 | pages=}} {{cite journal | author=Reach, W.T.; Franz, B.A.; Weiland, J.L. | title=The Three-Dimensional Structure of the Zodiacal Dust Bands | journal=Icarus| year=1997 | volume=127 | pages=461 | doi=10.1006/icar.1997.5704}} == Footnotes == {{reflist}} [[Category:Planetary science]] [[Category:Astronomical_objects]] [[zh:星際塵埃]]