Aldehydes and sugars from evolved precometary ice analogs: Importance of ices in astrochemical and prebiotic evolution

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 4; pp. 965 - 970
• Main Authors: de Marcellus, Pierre, Meinert, Cornelia, Myrgorodska, Iuliia, Nahon, Laurent, Buhse, Thomas, Le Sergeant d’Hendecourt, Louis, Meierhenrich, Uwe J.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 27.01.2015; National Acad Sciences
• Subjects: Aldehydes; Chemical synthesis; Mass spectrometry; Molecular chemistry; Organic chemicals; Photochemistry; Physical Sciences; Temperature effects; glycolaldehyde; precometary ices; glyceraldehyde; prebiotic evolution; astrochemistry
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1418602112

Evolved interstellar ices observed in dense protostellar molecular clouds may arguably be considered as part of precometary materials that will later fall on primitive telluric planets, bringing a wealth of complex organic compounds. In our laboratory, experiments reproducing the photo/thermochemical evolution of these ices are routinely performed. Following previous amino acid identifications in the resulting room temperature organic residues, we have searched for a different family of molecules of potential prebiotic interest. Using multidimensional gas chromatography coupled to time-of-flight mass spectrometry, we have detected 10 aldehydes, including the sugar-related glycolaldehyde and glyceraldehyde—two species considered as key prebiotic intermediates in the first steps toward the synthesis of ribonucleotides in a planetary environment. The presence of ammonia in water and methanol ice mixtures appears essential for the recovery of these aldehydes in the refractory organic residue at room temperature, although these products are free of nitrogen. We finally point out the importance of detecting aldehydes and sugars in extraterrestrial environments, in the gas phase of hot molecular clouds, and, more importantly, in comets and in primitive meteorites that have most probably seeded the Earth with organic material as early as 4.2 billion years ago. Significance In molecular clouds out of which stars and planetary systems form, simple solid-state molecules made in large part of H ₂O, CO, CO ₂, CH ₃OH, and NH ₃ are abundantly present. In these environments, energetic and thermal processes on these ices, which can be simulated in the laboratory, lead to complex organic matter. Possibly at the origin of the organic matter in our Solar System and incorporated into planetesimals, this material may be considered as a potential source for prebiotic chemistry on telluric planets, following a process that may be quite universal. The composition of these laboratory-evolved ices includes potentially prebiotic species such as amino acids and, as presented in this paper, aldehydes and sugars.