Prebiotic synthesis initiated in formaldehyde by laser plasma simulating high-velocity impacts

¹ J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejkova 3, 18223 Prague 8, Czech Republic
² Sorbonne Université, Muséum National d’Histoire Naturelle, UMR CNRS 7590, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, IMPMC, 75005 Paris, France
³ Charles University in Prague, Faculty of Science, Department of Physical and Macromolecular Chemistry, Albertov 2030, 12840 Prague 2, Czech Republic
⁴ Department of Radiation and Chemical Physics, Institute of Physics, Czech Academy of Sciences, Na Slovance 1999/2, 18221 Prague 8, Czech Republic
⁵ Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 1782/3, 182 00 Prague 8, Czech Republic
⁶ Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 61265 Brno, Czech Republic
e-mail: cassone@ibp.cz
⁷ CEITEC – Central European Institute of Technology, Masaryk University, Campus Bohnice, Kamenice 5, 62500 Brno, Czech Republic
⁸ University of Cambridge, Cavendish Astrophysics, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
⁹ Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 OQH, UK

Received: 8 March 2019
Accepted: 1 May 2019

Abstract

Context. It is well known that hydrogen cyanide and formamide can universally be considered as key molecules in prebiotic synthesis. Despite the fact that formamide has been detected in interplanetary and interstellar environments, other prebiotic species are far more abundant, including, for example, formaldehyde. However, several results indicate that formamide can play the role of important intermediate as well as that of a feedstock molecule in chemical abiogenesis. Diverse recently proposed scenarios of the origins of the first biopolymers show that liquid formamide environments could have been crucial for the formation of nucleobases, nucleosides, and for phosphorylation reactions, which lead to nucleotides.

Aims. Here we report on a wide exploration of the formaldehyde reaction network under plasma conditions mimicking an asteroid descent in an Earth-like atmosphere and its impact.

Methods. Dielectric breakdown using a high-power kJ-class laser system (PALS – Prague Asterix Laser System) along with quantum mechanical, ab initio molecular dynamics, and enhanced sampling simulations have been employed in order to mimic an asteroid impact plasma.

Results. Being more abundant than formamide both in interstellar and interplanetary environments, during the era of early and late heavy bombardment of Earth and other planets, formaldehyde might have been delivered on asteroids to young planets. In the presence of nitrogen-bearing species, this molecule has been reprocessed under plasma conditions mimicking the local environment of an impacting body. We show that plasma reprocessing of formaldehyde leads to the formation of several radical and molecular species along with formamide.

Conclusion. All the canonical nucleobases, the simplest amino acid (i.e., glycine), and the sugar ribose, have been detected after treatment of formaldehyde and nitrogen gas with dielectric breakdown. Our results, supported by quantum mechanical and enhanced sampling simulations, show that formaldehyde – by producing inter alia formamide – may have had the role of starting substance in prebiotic synthesis.