Mid-infrared reflectance spectroscopy of calcium-aluminium-rich inclusions to identify primitive near Earth asteroids

Melwani Daswani, Mohit; Morlok, Andreas; Wolters, Stephen and Grady, Monica (2014). Mid-infrared reflectance spectroscopy of calcium-aluminium-rich inclusions to identify primitive near Earth asteroids. In: National Astronomy Meeting (NAM2014), 23-26 Jun 2014, Portsmouth, UK.

Abstract

The recent availability of mid-IR spectroscopy from space telescopes has led to studies attempting to characterise the composition of near Earth asteroids (NEAs) by comparison to spectroscopic observations of meteorites in the laboratory (e.g. [1, 2]). Mid-IR of carbonaceous chondrite meteorites has also recently been in focus to identify primitive asteroids and the aqueous alteration processes occurring on them [3]. Of special interest among the components of carbonaceous chondrites are the refractory calcium-aluminium-rich inclusions (CAIs) because they are formed very early on in the solar system. We have gathered reflectance spectra in the 2.5-16.0 μm range of the phases (spinel, olivine, melilite, pyroxene, etc.) in CAI sections of meteorites Allende (CV3.3), Vigarano (CV3.3) and Ornans (CO3.3) with a Perkin Elmer AutoIMAGE FTIR microscope, and compared them to mid-IR spectra of several NEA targets (253 Mathilde, 243 Ida, 1917 Cuyo, and the target of OSIRIS-Rex mission 101955 Bennu) of the Spitzer Space Telescope's Infrared Spectrometer (IRS [4]). Spectra from Spitzer were extracted with an optimal extraction method [5] and corrected with a near earth thermal model [6]. Reflectance spectra obtained from the CAIs were compared to spectra in the Keck/NASA RELAB database [7]. Overall, we see some features on the surfaces of the observed asteroids that may correspond to the pristine CAIs from the chondrites, though identification of these features is not easy.

References: [1] Emery, J. P. et al. (2006) Icarus, 182, 496-512. [2] Lim, L. F. et al. (2011) Icarus, 213, 510-523. [3] Trigo-Rodriguez, J. M. et al. (2014) Mon. Not. R. Astron. Soc. 437, 227-240. [4] Houck, J. R. et al. (2004) Astron. Phy. J. Suppl. 154, 18-24. [5] Lebouteiller, V. et al. (2010) Publ. Astron. Soc. Pac., 122.888, 231-240. [6] Harris, A. W. (1998) Icarus 131, 291-301. [7] Pieters, C. M., and Hiroi, T. (2004). Lunar Planet. Sci. XXXV, # 1720.

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