A mineral-based origin of Earth’s initial hydrogen peroxide and molecular oxygen

Abstract

Terrestrial reactive oxygen species (ROS) may have played a central role in the formation of oxic environments and evolution of early life. The abiotic origin of ROS on the Archean Earth has been heavily studied, and ROS are conventionally thought to have originated from H 2 O/CO 2 dissociation. Here, we report experiments that lead to a mineral-based source of oxygen, rather than water alone. The mechanism involves ROS generation at abraded mineral–water interfaces in various geodynamic processes (e.g., water currents and earthquakes) which are active where free electrons are created via open-shell electrons and point defects, high pressure, water/ice interactions, and combinations of these processes. The experiments reported here show that quartz or silicate minerals may produce reactive oxygen-containing sites (≡SiO•, ≡SiOO•) that initially emerge in cleaving Si–O bonds in silicates and generate ROS during contact with water. Experimental isotope-labeling experiments show that the hydroxylation of the peroxy radical (≡SiOO•) is the predominant pathway for H 2 O 2 generation. This heterogeneous ROS production chemistry allows the transfer of oxygen atoms between water and rocks and alters their isotopic compositions. This process may be pervasive in the natural environment, and mineral-based production of H 2 O 2 and accompanying O 2 could occur on Earth and potentially on other terrestrial planets, providing initial oxidants and free oxygen, and be a component in the evolution of life and planetary habitability.

Silica particles convert thiol-containing molecules to disulfides

“…Coupling Reactions ( 23) and (25) with Reactions (47) and (48) we see the potentially important role that H2O + could play in the formation of both solution-phase OH• and surface-bound Si-O• radicals.…”

“…Also, although hydrogen peroxide H2O2 are known to form from stress-activated electric currents in rock as well as at silica/water interface of freshly fractured surfaces of abraded quartz, we did not introduce any intensive mechanical forces into the system and thus we do not observe the stress-induced or fracture-induced formation of hydrogen peroxide. (24,25) Also, sulfenic acid is a known intermediate when peroxide is present to oxidize thiols (RSH), (20) which was expected to show a [RSH + O]peak, but such a peak was not detected in high-resolution mass spectra throughout the kinetic processes. Dissolved molecular oxygen may be involved in the formation of disulfides as well, but while it may explain the measured oxidation products in the control it cannot explain the effects of silica particles.…”

Carbonyl Migration in Uronates Affords a Potential Prebiotic Pathway for Pentose Production

“…The Fenton reaction employing ferrous iron and H 2 O 2 is attractive from a prebiotic perspective because ferrous iron , and H 2 O 2 may have been geochemically available on early Earth. Fenton’s reagent has been reported by Larsen and Smidsrød to afford the oxidation of aldonic acids to uronic acids; however, the available analytical tools employed at the time of this study limited product identification.…”

“…While there is general consensus for the presence Fe­(II) in early aqueous systems, the geochemical production of H 2 O 2 during the Hadean may have been problematic, although there are recent suggestions that turbulent subaqueous environments can provide sufficient Archean H 2 O 2 . The production of H 2 O 2 has also been observed from silicate mineral weathering …”

Methanol on the rocks: green rust transformation promotes the oxidation of methane

“…During these periods, GRs are thought to have been abundant and likely shepherded marine geochemistry at the interface between land, air and sea [21,24,57]. Prior to the GOE and the subsequent proliferation of O 2 in marine environments, geochemically generated radical species [39,[58][59][60][61], thermochemical processes [22,62], natural electrochemical processes [63][64][65], photochemistry [23,61], nitrogen oxides [18,66] and nitrogen oxyanions [67,68], may have served as potential surrogates for the oxidation of GR and thus CH 4 , creating a CH 4 sink within the ancient Archean ocean. As O 2 concentrations increased following the GOE, the oxidation of GR-bearing oceans may have played a role in the drawdown of atmospheric CH 4 concentrations [10], impacting climate throughout the Proterozoic [69,70].…”