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RE: Interplanetary dust
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Look east to see ghostly Zodiacal Light
During the next few weeks on some clear moonless early morning, if you are fortunate to be far from any haze and bright lights, keep a close watch on the eastern horizon about two hours before sunrise. If you're lucky you might catch a glimpse of a ghostly column of light extending upward into the sky.

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Carbon From Outer Space Older Than Our Solar System
While looking at interplanetary dust particles (IDPs) found in the Earth's stratosphere, researchers from the Washington University in St. Louis have found carbon older than the Solar System. They identified the organic material by its carbon isotopic composition, different from the one of carbon found on Earth. (Isotopes are variations of elements that differ from each other in the number of neutrons they have, making them similar chemically but different physically.)

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Title: Sources of zodiacal dust
Authors: S.I. Ipatov

Fractions of asteroidal particles, particles originating beyond Jupiter's orbit (including trans-Neptunian particles), and cometary particles originating inside Jupiter's orbit among zodiacal dust are estimated to be about 1/3 each, with a possible deviation from 1/3 up to 0.1-0.2. These estimates were based on the comparison of our models of the zodiacal cloud that use results of numerical integration of the orbital evolution of dust particles produced by asteroids, comets, and trans-Neptunian objects with different observations (e.g., WHAM [Wisconsin H-Alpha Mapper spectrometer] observations of spectra of zodiacal light, the number density at different distances from the Sun). The fraction of particles produced by Encke-type comets (with e~0.8-0.9) does not exceed 0.15 of the overall population. The estimated fraction of particles produced by long-period and Halley-type comets among zodiacal dust also does not exceed 0.1-0.15. Though trans-Neptunian particles fit different observations of dust inside Jupiter's orbit, they cannot be dominant in the zodiacal cloud because studies of the distribution of number density with a distance from the Sun shows that trans-Neptunian particles cannot be dominant between orbits of Jupiter and Saturn. Mean eccentricities of zodiacal particles that better fit the WHAM observations were about 0.2-0.5, with a more probable value of about 0.3.

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Title: Evidence for dust accumulation just outside the orbit of Venus
Authors: Ch. Leinert, B. Moster

To contribute to the knowledge of dynamics of interplanetary dust we are searching for structures in the spatial distribution of interplanetary dust near the orbit of Venus. To this end we study the radial gradient of zodiacal light brightness, as observed by the zodiacal light photometer on board the Helios space probes on several orbits from 1975 to 1979. The cleanest data result from Helios B (= Helios 2) launched in January 1976. With respect to the general increase of zodiacal light brightness towards the Sun, the data show an excess brightness of a few percent for positions of the Helios space probe just outside the orbit of Venus. We consider this as evidence for a dust ring associated with the orbit of Venus, somewhat similar to that found earlier along the Earth's orbit.

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