Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth

Abstract

The much-studied Murchison meteorite is generally used as the standard reference for organic compounds in extraterrestrial material. Amino acids and other organic compounds important in contemporary biochemistry are thought to have been delivered to the early Earth by asteroids and comets, where they may have played a role in the origin of life. Polyhydroxylated compounds (polyols) such as sugars, sugar alcohols and sugar acids are vital to all known lifeforms-they are components of nucleic acids (RNA, DNA), cell membranes and also act as energy sources. But there has hitherto been no conclusive evidence for the existence of polyols in meteorites, leaving a gap in our understanding of the origins of biologically important organic compounds on Earth. Here we report that a variety of polyols are present in, and indigenous to, the Murchison and Murray meteorites in amounts comparable to amino acids. Analyses of water extracts indicate that extraterrestrial processes including photolysis and formaldehyde chemistry could account for the observed compounds. We conclude from this that polyols were present on the early Earth and therefore at least available for incorporation into the first forms of life.

El origen de la vida desde un punto de vista geológico

“…Estos últimos meteoritos se han asignado a un segundo grupo que se ha supuesto proveniente del cinturón de asteroides (Encyclopedia of Astrobiology, Astronomy, and Spaceflight). Cooper et al (2001) identificaron en el meteorito Murchison polioles, producto de la degradación de azúcares, relacionados con la ribosa y desoxirribosa, lo que ha puesto de manifiesto la existencia de la síntesis de azúcares en ambientes prebióticos, paso de suma importancia en el problema del origen de la vida (Antonio Lazcano, comunicación escrita, 4 de octubre de 2003).…”

Facula, Faculae

“…One significant advantage of this process is that sugars are generally much more stable at low temperatures (Larralde et al 1995). The eutectic freezing and thawing of precursor ice-grain organics such as HCHO in carbonaceous chondrites may have allowed for the synthesis of sugars on these bodies (Cooper et al 2001). The frozen clay model proposed by Lahav and Chang (1976) may warrant careful reconsideration.…”

“…Under the basic reaction conditions which allow the formose reaction to occur, sugar decomposition into tars (Reid and Orgel 1967;Shapiro 1988), furans, and other low molecular weight degradation products (De Bruijn et al 1986;Cooper et al 2001) is also facilitated (Larralde et al 1995). This has been shown to be less significant depending on the presence of high concentrations of inorganic species which may act as stabilizers Lambert et al 2010).…”

“…Polyols such as glycerol and ribitol have been identified in the Murchison meteorite, although the only actual sugar identified was DHA (Cooper et al 2001). This can potentially be explained by the instability of sugars over the $4 billion years since the Murchison parent body formed and the observed organic synthesis presumably occurred.…”

“…Both formaldehyde and ▶ glycolaldehyde have been observed spectroscopically in outer space in both the ▶ interstellar medium and in comets (Hollis et al 2000). Formaldehyde and sugar-related compounds, such as ▶ glycerol, which could be derived from this reaction are abundant in some carbonaceous chondrites (Cooper et al 2001); thus, the formose reaction could be a cosmically common abiotic mechanism for sugar synthesis.…”