S20A0149abst
S20A0149
A silicate feature is often observed in comet spectra as a 10-Β΅m resonant feature, and its appearance depends on the dust properties (size, crystallinity, porosity, etc.) of the comets. This feature can be an essential clue to probe the early solar nebula. Because the formation of the crystalline silicate grains requires high temperature, they are thought to be born from amorphous silicates at the inner region, and then transported toward the outer region where comets were born. This transportation can produce the difference in the fraction of crystalline in the silicate dust among comets. In addition to crystalline silicates, we recently found the unidentified infrared emission features, which could be attributed to aromatic and aliphatic hydrocarbons, in the mid-infrared spectrum of comet 21P/Giacobini-Zinner. This is the first firm detection of complex organic material features in the mid-infrared comet spectrum. Typical mass fraction of crystalline silicates in comet 21P suggests that organic materials in comet 21P originated from the warmer circumplanetary disk region of giant planets than the typical comet-forming region. We try to search for the organic features in other comets because this will be a precious opportunity to observe the cometary organic feature before the decommissioning of COMICS.
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