Hydrogen cyanide polymers, comets and the origin of life

Abstract

Hydrogen cyanide polymers--heterogeneous solids ranging in colour from yellow to orange to brown to black--could be major components of the dark matter observed on many bodies of the outer solar system including asteroids, moons, planets and, especially, comets. The presence on cometary nuclei of frozen volatiles such as methane, ammonia and water subjected to high energy sources makes them attractive sites for the ready formation and condensed-phase polymerization of hydrogen cyanide. This could account for the dark crust observed on Comet Halley in 1986 by the Vega and Giotto missions. Dust emanating from its nucleus would arise partly from HCN polymers as suggested by the Giotto detection of free hydrogen cyanide, CN radicals, solid particles consisting only of H, C and N, or only of H, C, N, O, and nitrogen-containing organic compounds. Further evidence for cometary HCN polymers could be expected from in situ analysis of the ejected material from Comet Tempel 1 after collision with the impactor probe from the two-stage Deep Impact mission on July 4, 2005. Even more revealing will be actual samples of dust collected from the coma of Comet Wild 2 by the Stardust mission, due to return to Earth in January 2006 for analyses which we have predicted will detect these polymers and related compounds. In situ results have already shown that nitriles and polymers of hydrogen cyanide are probable components of the cometary dust that struck the Cometary and Interstellar Dust Analyzer of the Stardust spacecraft as it approached Comet Wild 2 on January 2, 2004. Preliminary evidence (January 2005) obtained by the Huygens probe of the ongoing Cassini-Huygens mission to Saturn and its satellites indicates the presence of nitrogen-containing organic compounds in the refractory organic cores of the aerosols that give rise to the orange haze high in the atmosphere of Titan, Saturn's largest moon. Our continuing investigations suggest that HCN polymers are basically of two types: ladder structures with conjugated -C=N- bonds and polyamidines readily converted by water to polypeptides. Thermochemolysis GC-MS studies show that cleavage products of the polymer include alpha-amino acids, nitrogen heterocycles such as purines and pyrimidines, and provide evidence for peptide linkages. Hydrogen cyanide polymers are a plausible link between cosmochemistry and the origin of informational macromolecules. Implications for prebiotic chemistry are profound. Following persistent bolide bombardment, primitive Earth may have been covered by water and carbonaceous compounds, particularly HCN polymers which would have supplied essential components for establishing protein/nucleic acid life.

Prebiotic-chemistry inspired polymer coatings for biomedical and material science applications

“…Matthew's and Ferris' separate studies of HCN polymerization chemistry, as well as Sagan's and Khare's study of tholins, also involved the facile production of complex, highly colored organic polymers. [7][8][9][10][11][12][13][14][15] They have also been considered as a potential source of amino acids, nucleobases and peptides on earth and appear to be common throughout our solar system. For example, these materials have been proposed to be the source of the distinctive orange, redbrown and black colors of comets and the atmosphere of planets and moons such as Saturn, Jupiter and Titan and carbonaceous meteorites, indicating their abundance in our solar system and the universe, respectively.…”

“…For example, these materials have been proposed to be the source of the distinctive orange, redbrown and black colors of comets and the atmosphere of planets and moons such as Saturn, Jupiter and Titan and carbonaceous meteorites, indicating their abundance in our solar system and the universe, respectively. 10,[14][15][16] However, the focus of prebiotic chemistry has always been on understanding the chemical origin of life and thus has remained highly fundamental research. 4 The application of prebiotic chemistry and specifically prebiotic polymers to material science has not been reported.…”

Special Issue: Abstracts From the 2008 Issol Meeting

“…HCN is a ubiquitous molecule in the whole Universe and it is a main product in prebiotic simulation experiments (see e.g. Matthews and Minard, 2006, Chen and Chen, 2005, Saladino et al 2004. It has been proposed that the HCN polymers are important substances in the first stages of the chemical evolution to the emergence of life.…”

Organic matter in space - An overview

“…Besides tholins, HCN polymers have also been speculated to be part of the dark component present on outer Solar System bodies, including comets (Matthews & Minard 2006). It can also contribute to the orange haze in the stratosphere of Titan.…”