Characterization of insoluble organic matter in primitive meteorites by microRaman spectroscopy

Abstract

Abstract-We have analyzed the chemically and isotopically well-characterized insoluble organic matter (IOM) extracted from 51 unequilibrated chondrites (8 CR, 9 CM, 1 CI, 3 ungrouped C, 9 CO, 9 CV, 10 ordinary, 1 CB and 1 E chondrites) using confocal imaging Raman spectroscopy. The average Raman properties of the IOM, as parameterized by the peak characteristics of the so-called D and G bands, which originate from aromatic C rings, show systematic trends that are correlated with meteorite (sub-) classification and IOM chemical compositions. Processes that affect the Raman and chemical properties of the IOM, such as thermal metamorphism experienced on the parent bodies, terrestrial weathering and amorphization due to irradiation in space, have been identified. We established separate sequences of metamorphism for ordinary, CO, oxidized, and reduced CV chondrites. Several spectra from the most primitive chondrites reveal the presence of organic matter that has been amorphized. This amorphization, usually the result of sputtering processes or UV or particle irradiation, could have occurred during the formation of the organic material in interstellar or protoplanetary ices or, less likely, on the surface of the parent bodies or during the transport of the meteorites to Earth. D band widths and peak metamorphic temperatures are strongly correlated, allowing for a straightforward estimation of these temperatures.

A micro-Raman and infrared study of several Hayabusa category 3 (organic) particles

“…Depending on the level of disorder, the G-band shifts to higher wavenumbers and can be observed at around 1,600 cm is not present in the perfectly stacked graphite and it is induced by structural defects. Its size reflects increasing disorder (Busemann et al 2007;Quirico et al 2009). …”

“…The other is a rather primitive carbonaceous material that would be transported from space. Because IOM from the LL4-6 chondrites is scarce (in types 3.6 to 3.7 ordinary chondrites, most IOM has disappeared; Busemann et al 2007), the IOM sample was prepared from the Murchison CM2 chondrite as a primitive extraterrestrial material for comparison. The preparation method is described in Oba and Naraoka (2009).…”

First Measurement of the 14N/15N Ratio in the Analog of the Sun Progenitor OMC-2 FIR4

“…Based on the solar wind particles (Marty 2012), the Solar Nebula value is 441 ± 6. However, 14 N/ 15 N is 272 in the Earth atmosphere (Marty 2012), around 140 in comets (Manfroid et al 2009;Mumma & Charnley 2011;Shinnaka et al 2014;Rousselot et al 2014), and between 5 and 300 in meteorites (Busemann et al 2006;Bonal et al 2010;Aléon 2010). The Solar System primitive objects as well as the terrestrial atmosphere are, hence, enriched of 15 N with respect to the presumed initial value.…”

Organic materials in planetary and protoplanetary systems: nature or nurture?

“…These variations are controlled by heterogeneities in the precursors accreted by the parent bodies and by the effects of post-accretion processes (Cody & Alexander 2005;Quirico et al 2009). Post-accretion processes include low-temperature hydrothermalism (Cody & Alexander 2005;Yabuta et al 2005;Orthous-Daunay et al 2010a), long-duration radiogenic thermal metamorphism (Bonal et al 2006a(Bonal et al , 2007Busemann et al 2007), and short-duration thermal metamorphism (Yabuta et al 2010). IOM in interplanetary dust particules (IDPs) and antarctic micrometeorites (AMMs) has a fairly, but not strictly, similar polyaromatic structure to that of chondrites (Quirico et al 2005;Bonal et al 2006b;Dobrica et al 2009).…”