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Summary

Astrophysicists and planetary scientists are especially intrigued by the chondritic IDPs because they provide a link to the astrophysical conditions out of which our solar system formed.

We can follow the trail to the right in the diagram above to the IDPs that contain the most volatile and primitive elements. The trail takes us first from interplanetary dust particles to *chondritic* interplanetary dust particles. Planetary scientists classify chondritic IDPs in terms of their diminishing degree of oxidation so that they fall into three major groups: the carbonaneous, the ordinary, and the enstatite chondrites. As the name implies, the carbonaceous condrites are rich in carbon, and many have anomalies in the isotopic abundances of H, C, N, and O (Jessberger, 2000). From the carbonaceous chondrites, we follow the trail to the most primitive materials. They are almost completely oxidized and contain the most low condensation temperature elements ("volatile" elements) and the largest amount of organic compounds. Therefore, dust particles with these elements are thought to be formed in the early life of our solar system. Why? The volatile elements have never seen temperatures above about 500 K, therefore, one can conclude that the IDP grain "matrix" consists of some very primitive solar system material. Such a scenario is true in the case of comet dust (Gruen, 1999).

Gruen, E. "Interplanetary Dust and the Zodiacal Cloud", _Encyclopedia of the Solar System_, Academic Press, 1999 who uses this reference for Table III: Jessberger, E.K. et al., (1992), Earth Planet. Sci. Lett. 112, 91-99.

Graphic designed by Amara Graps, Planetary Science Institute, Tucson, Arizona, and released into the public domain December 28, 2006.

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