Prebiotic Significance of Extraterrestrial Ice Photochemistry: Detection of Hydantoin in Organic Residues

Abstract

The delivery of extraterrestrial organic materials to primitive Earth from meteorites or micrometeorites has long been postulated to be one of the origins of the prebiotic molecules involved in the subsequent apparition of life. Here, we report on experiments in which vacuum UV photo-irradiation of interstellar/circumstellar ice analogues containing H(2)O, CH(3)OH, and NH(3) led to the production of several molecules of prebiotic interest. These were recovered at room temperature in the semi-refractory, water-soluble residues after evaporation of the ice. In particular, we detected small quantities of hydantoin (2,4-imidazolidinedione), a species suspected to play an important role in the formation of poly- and oligopeptides. In addition, hydantoin is known to form under extraterrestrial, abiotic conditions, since it has been detected, along with various other derivatives, in the soluble part of organic matter of primitive carbonaceous meteorites. This result, together with other related experiments reported recently, points to the potential importance of the photochemistry of interstellar "dirty" ices in the formation of organics in Solar System materials. Such molecules could then have been delivered to the surface of primitive Earth, as well as other telluric (exo-) planets, to help trigger first prebiotic reactions with the capacity to lead to some form of primitive biomolecular activity.

The Photochemistry of Pyrimidine in Realistic Astrophysical Ices and the Production of Nucleobases

“…Most of these photoproducts are known to form via UV irradiation of ice mixtures containing CH 3 OH and NH 3 (Bernstein et al 1995;Muñoz Caro & Schutte 2003;Nuevo et al 2008Nuevo et al , 2012de Marcellus et al 2011), which are both present in the starting M1 and M2 ice mixtures, and likely do not require pyrimidine to form. For example, glycerol is most probably formed from the combination of three CH 3 OH molecules.…”

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

“…Among the numerous individual molecules detected in these residues, hexamethylenetetramine (HMT) is a dominant species (10-13), although it seems not to have any direct prebiotic implication (14). On the other hand, several molecules of potential prebiotic interest have been found, such as amino and diamino acids (14)(15)(16)(17)(18), hydantoin (19), urea and glycolic acid (6,20), lipid precursors (21), quinones when polycyclic aromatic hydrocarbons are irradiated in water ice (22), and even nucleobases-however, only when pyrimidine is added to the initial ice mixture (23)(24)(25). The presence of sugars, in particular those included in nucleotides that are the building blocks of nucleic acids, has never been reported in these residues.…”

E

“…Vacuum UV photo-irradiation of simpler ices containing H 2 O, CH 3 OH, and NH 3 led to the production of hydantoin, 2,4-imidazolidinedione (De Marcellus et al 2011), a molecule suspected to play an important role in the formation of oligopeptides. Hydantoin is known to form under extraterrestrial conditions, since it has been detected in the soluble organic fraction of primitive carbonaceous meteorites.…”