Mid-IR, Far-IR, Raman micro-spectroscopy, and FESEM–EDX study of IDP L2021C5: Clues to its origin R. Brunetto a,b,⇑ , J. Borg a , E. Dartois a , F.J.M. Rietmeijer c , F. Grossemy a , C. Sandt d , L. Le Sergeant d’Hendecourt a , A. Rotundi b , P. Dumas d , Z. Djouadi a , F. Jamme d a Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Université Paris-Sud, bâtiment 121, F-91405 Orsay Cedex, France b Dip. Scienze Applicate, Università degli Studi di Napoli ‘‘Parthenope’’, Centro Direzionale, I-80143 Napoli, Italy c Department of Earth and Planetary Sciences, MSC 03-2040, 1-University of New Mexico, Albuquerque, NM 87131-0001, USA d Synchrotron SOLEIL, L’Orme des Merisiers, Saint-Aubin – BP 48, F-91192 Gif-sur-Yvette Cedex, France article info Article history: Received 14 June 2010 Revised 27 January 2011 Accepted 30 January 2011 Keywords: Spectroscopy Experimental techniques Interplanetary dust Comets abstract Interplanetary Dust Particles (IDPs) are potentially of cometary origin. They may therefore provide important clues to a better understanding of the early Solar System physical and chemical conditions. A chondritic porous aggregate IDP (named L2021C5) was analyzed using mid to far FTIR (2–60 lm) micro-spectroscopy, Raman micro-spectroscopy, field-emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analyses. The IDP was pressed between diamond windows to increase the quality of the spectral data by overcoming the diffraction limitation and minimizing light scattering effects from particles of a global size similar to the wavelength of the observation. This combination of techniques has enabled a mineralogical, organic and compositional description of the compressed parti- cle. The IR spectra show that in L2021C5 amorphous silicates are more abundant than crystalline ones, and that the crystalline component is richer in olivine than in pyroxene. The composition and distribution of these inorganic components match very well the small silicate grains emission observed for comet Hale-Bopp from ISO-SWS spectra. Raman spectroscopy has allowed the detection of carbonaceous struc- tures displaying different degrees of order, covering almost the whole range observed so far for IDPs. The combination of the three analytical techniques indicates that L2021C5 is a low-Ca, chondritic porous aggregate that experienced only mild flash heating on atmospheric entry, as indicated by the disordered carbon properties, the Fe/S atomic ratio of sulfides, the absence of Na depletion, and the small depletion of S. Based on a plausible cometary origin and on the estimated low entry velocity, we suggest that this IDP came from the Zodiacal cloud that is dominated by dust from Jupiter-Family comets. Ó 2011 Elsevier Inc. All rights reserved. 1. Introduction Planetesimals of our Solar System formed in less than 10 Myr after the collapse of a dense region in a molecular cloud had started (Montmerle et al., 2006). Some of the physical and chemical conditions may have been preserved in the primordial solar nebula material present in objects not too heavily modified by parent body processes since that early period, such as comets. Interplanetary Dust Particles (IDPs), with typical sizes 10– 30 lm, may have asteroidal or cometary origins (Thomas et al., 1995; Messenger, 2000). In particular, He release patterns in IDPs, giving indirect proof for their entry velocity in the atmosphere, indicate an origin of some IDPs from comets (see Bradley, 2003, and references therein). Their classification, using a combination of chemical and textural constraints, into various families gives clues to their origin. Chemically, IDPs are divided into two main families: chondritic and non-chondritic IDPs (Rietmeijer, 1998). In chondritic IDPs, the abundances of Mg, Al, Si, S, Ca, Ti, Cr, Mn, Fe, and Ni are typically within factors of 2–3 of those measured in CI carbonaceous chondrites. CI chondrite compositions are thought to closely resemble that of the non-volatile component of the solar nebula. Non-chondritic IDPs typically have Fe-sulfide, Mg-silicate and refractory mineral compositions (Rietmeijer, 1998, 2002). IDPs can, in addition, be classified according to their morphology as porous aggregates or compact particles. Brownlee (1978) suggested that the combination of a porous morphology and chondritic (i.e. CI) composition of an aggregate IDP is a strong indicator for an extraterrestrial origin. Such chondritic porous (CP) IDPs are generally considered to have originated from comets, or P-type or D-type asteroids, but in any case they are not from the parent bodies of any meteorites in our collections (e.g. Bradley 0019-1035/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.icarus.2011.01.038 ⇑ Corresponding author at: Institut d’Astrophysique Spatiale, CNRS, UMR-8617, Université Paris-Sud, bâtiment 121, F-91405 Orsay Cedex, France. Fax: +33 169858675. E-mail address: rosario.brunetto@ias.u-psud.fr (R. Brunetto). Icarus 212 (2011) 896–910 Contents lists available at ScienceDirect Icarus journal homepage: www.elsevier.com/locate/icarus