Abstract

A first attempt to characterize powder samples of primitive meteorites found in the Atacama Desert, Chile, by infrared (IR) spectroscopy is presented in this work. The samples were rst studied by [1] and correspond to ve H ordinary chondrites (OCs), fourteen L-LL OCs and three carbonaceous chondrites (CCs) type CO3, all affected by terrestrial weathering (W parameter, de ned by [2]) to some degree. These kind of meteorites are the building blocks of planets, showing in their mineral assemblages and textures the keys to understand primary processes in the formation of the rst solids in the Solar System, as well as secondary and tertiary processes occurring once planetesimals started to grow and became proto-planets. For this reason is one of the best materials to characterize in order to compare with the data coming from IR spectroscopy from protoplanetary disks (PPDs). The main goal of this study is to compare the spectra of each sample to other published spectra of different meteorite materials and PPDs, as the work of [3] and [4], in order to check the influence of weathering and main composition. The absorbance pattern of all the OCs and CCS shows the most important peaks associated with the main ferromagnesian silicates common to this kind of meteorites at the wavelength range between 8 – 13 um: olivines (stronger at 11,2 um and 20 um) and pyroxenes (stronger at 9,5 um and 10,7 um). OCs display a same pattern but with different intensities of absorbance, being the less weathered (W1) Lutchauning’s stone the one that appears to have more absorption in the set of samples, while the highly shocked (S5) Pampa C, has a distinctive pattern with smooth and low absorbance peak around the 8-13 um wavelength range, showing that high weathering and high shock can decrease the absorbance pattern of meteorite spectra, in a rst analysis. Other observation is that CCs are very distinctive from OCs showing less peaks associated with olivine – pyroxene assemblages, and other peaks close to ~7 um that has been referred to organic materials [4]. Further analyses will help to constraint all the parameters involved to better understand the signature in IR spectroscopy to compare with IR spectra from PPDs obtained with the Spitzer Space Telescope. References: [1] Valenzuela, M. 2011. PhD thesis. University of Chile 201p; [2] Wlotzka, 1993. Meteoritics 28, p. 460; [3] Morlok et al. 2012. Icarus 219, p.48-56;[4] Morlok et al. 2014, Icarus 239, p.1-14.