Mid-infrared spectroscopic investigation of meteorites and perspectives for thermal infrared observations at the binary asteroid Didymos

摘要

Near future missions to Near Earth Asteroids could provide new information exploiting the middle-infrared (2.5- 25 mu m) region, as at the temperature range of asteroids at Earth' solar distance the maximal energy is emitted in this region. The IR range is ideal for the analysis and separation of various silicate types. This work reviews the background knowledge and evaluates the possibilities for mineral identification using high resolution laboratory data. Examples are presented using laboratory based meteorite powder data to evaluate the possibility for identification of plagioclase, estimation on the Mg/(Mg thorn Fe) ratio and other characteristics. The expected peak position shift from temperature differences on a rotating asteroid might be below 0.01 mu m, while the fine structure of bands requires high spectral resolution as well. However, with moderate resolution, the analysis of three main minerals is still possible, focusing at the range of 12.5-9.09 mu m (800-1100 cm(-1)) with spectral resolution of about 0.08 mu m (10 cm(-1)), to identify the expected main bands of olivine, pyroxene and feldspars.An infrared camera at small orbital distance around the target could resolve fine powder covered areas like dust ponds or separate blocks. For this task an angular resolution below 0.05 degrees might be required. Such observations would provide a wide range of important data both on surface composition, granular processes and space weathering on asteroid surfaces. However, further targeted laboratory analysis is necessary, especially using pure minerals of different grain size and meteorite powder mixtures.