Mass-independent oxygen isotope fractionation driven by energetic-particle irradiation of icy solids
Year: 2026
Type: article
Abstract: Mass-independent isotope fractionation (MIF) of oxygen provides key insights into atmospheric chemistry and the origin of isotopic anomalies in planetary materials. To date, MIF has been primarily associated with gas-phase processes involving symmetry-dependent reaction pathways, most notably ozone formation. Whether analogous effects can arise in condensed phases or at interfaces remains an open question. Here we report laboratory experiments demonstrating that energetic particle irradiation of icy oxide surfaces produces mass-independent oxygen isotope fractionation at temperatures as low as 10 K. Electron irradiation of SiO 2 and Al 2 O 3 substrates in the presence of H 2 O ice results in measurable shifts in Δ 17 O in the underlying solids. The resulting three-isotope relationships include slope-1-like behavior in SiO 2 and Al 2 O 3 and distinct, substrate-dependent trends in Al 2 O 3 , indicating that irradiation-induced defect formation and interfacial chemistry govern the isotope effects. The magnitude of the observed anomalies demonstrates that irradiation-driven processes can generate substantial oxygen isotope heterogeneity in condensed phases. These results identify a previously unrecognized class of MIF and provide a quantitative framework for interpreting oxygen isotope signatures in radiation-processed environments, including interstellar grains and early solar system materials.
Language: English
Topic: Astro and Planetary Science
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
Awards: G3112974993, G3793783379, Facility Support: The UCLA National Ion Microprobe, MULTI-ISOTOPIC MEASUREMENTS OF OZONE FORMATION ON INTERSTELLAR DUST GRAIN ANALOGSDECADES OF MULTI-OXYGEN ISOTOPIC MEASUREMENTS OF PLANETARY MATERIALS HAVE SHOWN THAT THE DISTRIBUTION OF OXYGEN ISOTOPES IN THE SOLAR SYSTEM IS ANOMALOUS AND CANNOT BE EXPLAINED BY CONVENTIONAL MASS-DEPENDENT ISOTOPIC FRACTIONATION PROCESSES. BECAUSE OF THE CENTRAL IMPORTANCE THAT OXYGEN HAS AS BOTH A REFRACTORY AND VOLATILE ELEMENT UNDERSTANDING THE PHYSICAL-CHEMICAL PROCESSES RESPONSIBLE FOR THE DISTRIBUTION OF OXYGEN ISOTOPES IN THE SOLAR SYSTEM AS REVEALED BY STUDIES OF METEORITES AND THE GENESIS MISSION IS ESSENTIAL FOR ADVANCING OUR UNDERSTANDING OF THE FORMATION AND EVOLUTION OF THE SOLAR SYSTEM. BASED ON THE WELL-KNOWN MASSINDEPENDENT OXYGEN ISOTOPE EFFECT OF OZONE IN THE GAS-PHASE IT WAS RECENTLY PROPOSED THAT THE FORMATION OF OZONE A LIKELY PRECURSOR TOWATER ON COLD DUST GRAINS IN DENSE MOLECULAR CLOUDS MAY BE RESPONSIBLE FOR THE ANOMALOUS DISTRIBUTION OF OXYGEN ISOTOPES IN THE SOLAR SYSTEM. HERE WE PROPOSE SYSTEMATIC LABORATORY STUDIES OF OZONE FORMATION ON COLD DUST GRAIN SURFACES TO TEST THE HYPOTHESIS THAT DUST GRAIN PHOTOCHEMISTRY MAY BE RESPONSIBLE FOR THE MASS-INDEPENDENT DISTRIBUTIONS OF OXYGEN ISOTOPES IN THE SOLAR SYSTEM., G5827637372, G6247749468, Community Facility Support: The UCLA National Ion Microprobe, RUI: Resolving Astrophysical Water Formation Pathways on Dust Grain Surfaces
OpenAlex ID: W7223087966