Can lightning produce significant levels of mass‐independent oxygen isotopic fractionation in nebular dust?

Abstract

Abstract-Based on recent evidence that oxide grains condensed from a plasma will contain oxygen that is mass-independently fractionated compared to the initial composition of the vapor, we present a first attempt to evaluate the potential magnitude of this effect on dust in the primitive solar nebula. This assessment relies on previous studies of nebular lightning to provide reasonable ranges of physical parameters to form a very simple model to evaluate the plausibility that lightning could affect a significant fraction of nebular dust and that such effects could cause a significant change in the oxygen isotopic composition of solids in the solar nebula over time. If only a small fraction of the accretion energy is dissipated as lightning over the volume of the inner solar nebula, then a large fraction of nebular dust will be exposed to lightning. If the temperature of such bolts is a few percent of the temperatures measured in terrestrial discharges, then dust will vaporize and recondense in an ionized environment. Finally, if only a small average decrease is assumed in the 16 O content of freshly condensed dust, then over the last 5 Myr of nebular accretion the average D 17 O of the dust could increase by more than 30 per mil. We conclude that it is possible that the measured "slope 1" oxygen isotope line measured in meteorites and their components represents a time-evolution sequence of nebular dust over the last several million years of nebular evolution where 16 O-rich materials formed first, then escaped further processing as the average isotopic composition of the dust gradually became increasingly depleted in 16 O.

Electrostatic activation of prebiotic chemistry in substellar atmospheres

“…A similar yield of amino acids was also found in experiments carried out to investigate prebiotic synthesis in steam-rich volcanic eruptions (Johnson et al, 2008). Nebular lightning has also been postulated as a mechanism for the processing of nebular dust in order to explain the oxygen isotopic content in the solar system (Nuth et al, 2012).…”

“…Nebular lightning has also been postulated as a mechanism for the processing of nebular dust in order to explain the oxygen isotopic content in the Solar system (Nuth et al . 2012).…”

Isotopic Dichotomy among Meteorites and Its Bearing on the Protoplanetary Disk

“…Mass-independent oxygen isotopic variations among CAIs and chondrules ( Figure 1) were once thought to be nucleosynthetic in origin (Clayton et al 1973), but are now thought to reflect a chemical process in the molecular cloud and/or the disk. These processes include photochemical dissociation of CO (Clayton 2002;Yurimoto & Kuramoto 2004;Lyons & Young 2005), surface reactions on dust grains in the molecular cloud (Dominguez 2010), and lightning in the disk (Nuth et al 2012). Enrichment of the heavier and rarer oxygen isotopes, 17 O and 18 O, is required to account for the very 16 O-depleted magnetite in socalled cosmic symplectite discovered in the ungrouped carbonaceous chondrite Acfer 094 (Sakamoto et al 2007;Seto et al 2008) as well as the evidence in many chondrites for asteroidal alteration by 16 O-poor aqueous fluids (Choi et al 1998;Krot et al 2015).…”

Did a Complex Carbon Cycle Operate in the Inner Solar System?

“…These processes would have two major consequences. First, the conversion of CO into more reactive carbonaceous species breaks down the assumed stable C 16 O reservoir that is required for the CO self-shielding mechanism [34][35][36][37] to enrich the Solar Nebula in heavier oxygen isotopes and produce mass independent oxygen isotopic fractionation in such meteoritic components as CAIs and chondrules [38,39]. Second, solid carbon fibers are much more easily incorporated into growing planetesimals in the warm inner solar nebula than would be the host of gaseous hydrocarbons generated by SMRs [9].…”