The deuterium/hydrogen distribution in chondritic organic matter attests to early ionizing irradiation

Abstract

Primitive carbonaceous chondrites contain a large array of organic compounds dominated by insoluble organic matter (IOM). A striking feature of this IOM is the systematic enrichment in deuterium compared with the solar hydrogen reservoir. This enrichment has been taken as a sign of low-temperature ion-molecule or gas-grain reactions. However, the extent to which Solar System processes, especially ionizing radiation, can affect D/H ratios is largely unknown. Here, we report the effects of electron irradiation on the hydrogen isotopic composition of organic precursors containing different functional groups. From an initial terrestrial composition, overall D-enrichments and differential intramolecular fractionations comparable with those measured in the Orgueil meteorite were induced. Therefore, ionizing radiation can quantitatively explain the deuteration of organics in some carbonaceous chondrites. For these meteorites, the precursors of the IOM may have had the same isotopic composition as the main water reservoirs of the inner Solar System.

Hydrothermal evolution of the morphology, molecular composition, and distribution of organic matter in CR (Renazzo‐type) chondrites

“…; Laurent et al. , ). Alternatively, they may have originated from different soluble precursors that led to different IOM signatures upon hydrothermal processing.…”

Probing molecular and isotopic features of meteoritic insoluble organic matter by solid‐state nuclear magnetic resonance spectroscopy with sub‐milligram sample

“…; Laurent et al. ). It was also suggested that the oxidation of iron by water on the parent body may have induced large D‐enrichment in organic matter (Alexander et al.…”

“…), the protosolar nebula (Willacy and Woods ; Laurent et al. ), and in the parent body (Eiler and Kitchen ). Among different possible processes, the effects of electron irradiation in the solar nebula have been proposed recently to account for large D‐enrichments in organic matter (Le Guillou et al.…”

“…13 C CP/MAS spectrum recorded on a 900 MHz spectrometer at 100 kHz MAS rate with 1.0 ms RAMP-CP contact time at n = À1 condition of CP matching profile and a 1.5 s recycle delay (total experimental time = 13.5 h) using 0.18 mg of IOM in a 0.75 mm diameter rotor. result of processes taking place in the interstellar medium (Yang and Epstein 1983;Sandford et al 2001;Busemann et al 2006), the protosolar nebula (Willacy and Woods 2009;Laurent et al 2015), and in the parent body (Eiler and Kitchen 2004). Among different possible processes, the effects of electron irradiation in the solar nebula have been proposed recently to account for large D-enrichments in organic matter (Le Guillou et al 2013;Laurent et al 2015).…”

“…result of processes taking place in the interstellar medium (Yang and Epstein 1983;Sandford et al 2001;Busemann et al 2006), the protosolar nebula (Willacy and Woods 2009;Laurent et al 2015), and in the parent body (Eiler and Kitchen 2004). Among different possible processes, the effects of electron irradiation in the solar nebula have been proposed recently to account for large D-enrichments in organic matter (Le Guillou et al 2013;Laurent et al 2015). It was also suggested that the oxidation of iron by water on the parent body may have induced large D-enrichment in organic matter (Alexander et al 2010).…”