Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 110 (25), 10089-94

Evidence for Reactive Reduced Phosphorus Species in the Early Archean Ocean

Affiliations

Evidence for Reactive Reduced Phosphorus Species in the Early Archean Ocean

Matthew A Pasek et al. Proc Natl Acad Sci U S A.

Abstract

It has been hypothesized that before the emergence of modern DNA-RNA-protein life, biology evolved from an "RNA world." However, synthesizing RNA and other organophosphates under plausible early Earth conditions has proved difficult, with the incorporation of phosphorus (P) causing a particular problem because phosphate, where most environmental P resides, is relatively insoluble and unreactive. Recently, it has been proposed that during the Hadean-Archean heavy bombardment by extraterrestrial impactors, meteorites would have provided reactive P in the form of the iron-nickel phosphide mineral schreibersite. This reacts in water, releasing soluble and reactive reduced P species, such as phosphite, that could then be readily incorporated into prebiotic molecules. Here, we report the occurrence of phosphite in early Archean marine carbonates at levels indicating that this was an abundant dissolved species in the ocean before 3.5 Ga. Additionally, we show that schreibersite readily reacts with an aqueous solution of glycerol to generate phosphite and the membrane biomolecule glycerol-phosphate under mild thermal conditions, with this synthesis using a mineral source of P. Phosphite derived from schreibersite was, hence, a plausible reagent in the prebiotic synthesis of phosphorylated biomolecules and was also present on the early Earth in quantities large enough to have affected the redox state of P in the ocean. Phosphorylated biomolecules like RNA may, thus, have first formed from the reaction of reduced P species with the prebiotic organic milieu on the early Earth.

Keywords: astrobiology; exobiology; origin of life; phosphorylation; prebiotic chemistry.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Geological map of the East Strelley Belt, with regional location shown (Inset). The box shows outline of the study area.
Fig. 2.
Fig. 2.
Stratigraphic column of tephra-carbonate sequence in the middle section of the Coucal Fm. in the Coonterunah Subgroup, Australia. Rock types are denoted by different colors, and all have been metamorphosed to at least greenschist facies. These rocks sit within the stratigraphic sequence shown in the center column, with arrows denoting the carbonate, chert, and pelitic samples investigated, and clast size shown as width of layers. This study section is a small portion of the Warrawoona group (right column), which consists of metavolcanic (V) and metasedimentary early Archean rocks, crosscut by chert dikes (x, +).
Fig. 3.
Fig. 3.
Outcrop photographs of Coonterunah carbonate, with magnetitic (m1 to m4) and carbonate (c1 to c3) mesobands labeled. (A) Calcitic phase: alternating calcite and magnetite laminae. (B) Dolomitic phase: alternating dolomite/calcite and magnetite laminae. The c1 mesoband is partially silicified. (C) Slabs through dolomitic phase.
Fig. 4.
Fig. 4.
Chromatogram showing P speciation of two samples of the Coonterunah carbonate (ALS-A and ALS-B) and of a hydrothermal control sample (ALS-C). P3+ is phosphite. No P species appeared within the 18.2 MΩ deionized water blank, and only phosphate (P5+) appeared in extracts of the other rocks listed in Table 1. These peaks correspond to concentration ratios (P3+/P total) of 40% (ALS-A) and 67% (ALS-B). Slight shifts in peak locations are attributable to peak wander as experiments run and are constrained by comparison with standards every five samples.
Fig. 5.
Fig. 5.
31P NMR spectrum of schreibersite added to a 0.5 M aqueous solution of glycerol at neutral pH and heated to 65 °C under argon. The spectrum was acquired fully coupled to hydrogen. The peaks are identified by comparison with a glycerol phosphate standard and by their J-coupling constants. The triplet results from CH2–O–P on the terminal end of glycerol, and the doublet results from a CH–O–P interaction on the second carbon of glycerol. The presence of glycerol phosphate is also confirmed by mass spectrometry, with a peak at 171 m/z in negative ion mode.

Similar articles

See all similar articles

Cited by 36 articles

See all "Cited by" articles

Publication types

LinkOut - more resources

Feedback