11:15 AM - 11:30 AM
[PCG23-09] Comparison of grain properties in interplanetary dust from different types of parent bodies by mid-infrared spectroscopic observations with AKARI
We obtained the high signal-to-noise zodiacal emission spectra at 74 different directions of the sky by using the mid-infrared slit-spectroscopic data obtained with the Infrared Camera on board the Japanese AKARI satellite. They exhibit the excess emission feature at the 9-12 μm range and even some sharp peaks. In order to identify the constituents, we compared the shape of spectral featureswith absorption coefficients of 4 types ofcandidate materials: amorphous with olivine composition, amorphous with pyroxene composition, forsterite (Mg2SiO4, one of olivine crystals), and ortho-enstatite (MgSiO3, one of pyroxene crystals).
The IPD was found to typicallyinclude small silicate crystals, especially enstatite grains with extreme crystal morphologies. We also found that the shape of spectral features slightly changesdependingon the sky directions.As the result of the investigation into peak wavelengths and the excess strength of each peak, the IPD at the higher ecliptic latitudes seems to have lower olivine/(olivine+pyroxene) ratio.At the sky directions toward the asteroidal dust band structures, the feature shapes show a difference which cannot be explained only by the difference in theolivine/(olivine+pyroxene) ratioand may indicate contamination of the hydrated minerals.
We will present the results of the grain properties of the IPD originating from some types of the parent bodies, and give the implications for the environment in the proto-solar system.