Exploring Refractory Organics in Extraterrestrial Particles

Abstract

The origin of organic compounds detected in meteorites and comets, some of which could have served as precursors of life on Earth, remains an open question. The aim of the present study is to make one more step in revealing the nature and composition of organic materials of extraterrestrial particles by comparing infrared spectra of laboratory-made refractory organic residues to spectra of cometary particles returned by the Stardust mission, interplanetary dust particles, and meteorites. Our results reinforce the idea of a pathway for the formation of refractory organics through energetic and thermal processing of molecular ices in the solar nebula. There is also the possibility that some of the organic material had formed already in the parental molecular cloud before it entered the solar nebula. The majority of the IR “organic” bands of the studied extraterrestrial particles can be reproduced in the spectra of the laboratory organic residues. We confirm the detection of water, nitriles, hydrocarbons, and carbonates in extraterrestrial particles and link it to the formation location of the particles in the outer regions of the solar nebula. To clarify the genesis of the species, high-sensitivity observations in combination with laboratory measurements like those presented in this paper are needed. Thus, this study presents one more piece of the puzzle of the origin of water and organic compounds on Earth and motivation for future collaborative laboratory and observational projects.

Trapped Water on Silicates in the Laboratory and in Astrophysical Environments

“…Based on the combination of laboratory data and IR observations, evidence of the presence of solid-state water in the diffuse ISM has been provided (Potapov et al 2021). Furthermore, a recent comparison of IR spectra of laboratorymade refractory organic residues on silicates to the spectra of cometary particles returned by the Stardust mission, interplanetary dust particles, and meteorites speaks for the presence of trapped water in these extraterrestrial particles (Potapov et al 2022). We note that trapped water originates from silicate/ice mixing at low temperatures and has no relation (maybe only as a possible precursor) to phyllosilicates, which also present great interest as possible solid-state water reservoirs at high temperatures, as they can retain water when heated up to a few hundreds of degrees centigrade (e.g., Davies 1996;Beck et al 2014;D'Angelo et al 2019;Thi et al 2020; and see also Elmi et al 2016 for a review).…”