Cometary Materials Originating from Interstellar Ices: Clues from Laboratory Experiments

Abstract

We use laboratory experiments to derive information on the chemistry occurring during the evolution of astrophysical ices from dense molecular clouds to interplanetary objects. Through a new strategy that consists of coupling very high resolution mass spectrometry and infrared spectroscopy (FT-IR), we investigate the molecular content of the organic residues synthesized from different initial ice compositions. We also obtain information on the evolution of the soluble part of the residues after their over-irradiation. The results give insight into the role of water ice as a trapping and diluting agent during the chemical evolution. They also give information about the importance of the amount of ammonia in such ices, particularly regarding its competition with the carbon chemistry. All of these results allow us to build a first mapping of the evolution of soluble organic matter based on its chemical and physical history. Furthermore, our results suggest that interstellar ices should lead to organic materials enriched in heteroatoms that present similarities with cometary materials but strongly differ from meteoritic organic material, especially in their C/N ratios.

On the Production of Polyols and Hydroxycarboxylic Acids in Interstellar Analogous Ices of Methanol

“…Previous studies have investigated the effects of each precursor on products properties (Bernstein et al 1995;Muñoz Caro & Schutte 2003;Nuevo et al 2011;Henderson & Gudipati 2015;Abou Mrad et al 2017;Fresneau et al 2017). Methanol was found to be the most reactive species and the main source of oxygen in products (Bernstein, et al 1995;Henderson & Gudipati 2015;Fresneau, et al 2017). The fraction of ammonia in the precursors does not alter the O/C ratio of the products significantly (Fresneau, et al 2017).…”

“…The differences between the present work and previous studies are radiation sources (energetic electrons vs UV photons), energy doses, and ice compositions (CH3 18 OH vs 13 CH3OH:NH3:H2O and 13 CH3OH: H2O). Previous studies have investigated the effects of each precursor on products properties (Bernstein et al 1995;Muñoz Caro & Schutte 2003;Nuevo et al 2011;Henderson & Gudipati 2015;Abou Mrad et al 2017;Fresneau et al 2017). Methanol was found to be the most reactive species and the main source of oxygen in products (Bernstein, et al 1995;Henderson & Gudipati 2015;Fresneau, et al 2017).…”

“…Methanol was found to be the most reactive species and the main source of oxygen in products (Bernstein, et al 1995;Henderson & Gudipati 2015;Fresneau, et al 2017). The fraction of ammonia in the precursors does not alter the O/C ratio of the products significantly (Fresneau, et al 2017). An excess of H2O can increase the abundance of more complex molecules due to molecular trapping effects (Fresneau, et al 2017), which may explain why high order sugars are missing in this study as our precursor is only pure methanol.…”

“…The fraction of ammonia in the precursors does not alter the O/C ratio of the products significantly (Fresneau, et al 2017). An excess of H2O can increase the abundance of more complex molecules due to molecular trapping effects (Fresneau, et al 2017), which may explain why high order sugars are missing in this study as our precursor is only pure methanol. We do not rule out the possibility of more complex 13 sugars in our residues but out of detection limit since the generation efficiency decreases upon increasing of molecular complexity (Abou Mrad, et al 2016) and our analytical protocol did not specifically target sugar molecules.…”

The Amino Acid Distribution in Laboratory Analogs of Extraterrestrial Organic Matter: A Comparison to CM Chondrites

“…The important requirement to form such molecules is that the starting ice mixtures must contain the four elements C, H, O, and N and roughly follow relative cosmic abundances. In addition, recent experiments in which the relative amount of water in the initial ice mixture is varied by a factor of 3, clearly show that varying the ice composition does not influence much the chemistry of the obtained organic residues (Fresneau et al 2017). Increasing significantly the radiation dose leads to insoluble organic residues (de Marcellus et al 2017).…”