Revisiting the particle-size constraint of the 10-μm silicate feature

1,2Ekaterina Chornaya,1Alexander M.Zakharenko,3Evgenij Zubko,1,4Aleksandr Kuchmizhak,1Kirill S.Golokhvast,5,6Gorden Videen
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2020.113907]
1Far Eastern Federal University, 8 Sukhanova St., Vladivostok 690950, Russia
2Institute of Applied Astronomy of RAS, 10 Kutuzova Emb., Saint-Petersburg 191187, Russia
3Humanitas College, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, South Korea
4Institute of Automation and Control Processes FEB RAS, 5 Radio St., Vladivostok 690041, Russia
5Space Science Institute, 4750 Walnut Street, Boulder, Suite 205, CO 80301, USA
6Department of Astronomy and Space Science, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104, South Korea
Copyright Elsevier

We experimentally measure the mid-IR spectra of half-millimeter-sized olivine particles with very compact morphology and smooth surfaces. We find that the 10-μm silicate feature is present in these large, irregularly shaped samples having surface roughness that is much smaller than optical wavelengths. Based on Mie theory, which assumes the particles are spherical, this feature should not exist for such large particles. As a consequence, its presence has been taken as an indicator that the particles or grains composing such particles were micron-sized or smaller. The measurement of this feature in real, irregularly shaped particles, suggests that the assumption of sphericity may severely limit our interpretations of remote-sensing data.

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