Meteoritic Molybdenum and Ruthenium Isotopic Abundances Document Nucleosynthetic p-process Components

Abstract

Anomalies in isotopic abundances of Mo and Ru in solar system matter were found to document variable contributions of the nucleosynthetic s -process component. We report isotopic relations of ϵ ^92 Mo versus ϵ ^100 Ru in meteorites from chondritic parent bodies, iron meteorites, and achondrites that reveal deviations from expected s -process abundance variations. We show that two p -process isotopes ^92 Mo and ^94 Mo require the presence of distinct p -process components in meteoritic materials. The nucleosynthetic origin of abundant magic ( N = 50) p -process nuclides, covering the mass range of Zr, Mo, and Ru, has long been an enigma, but contributions by several recognized pathways, including alpha and νp -antineutrino reactions on protons, may account for the observed relatively large solar system abundances. Specific core-collapse supernovae explosive regions may carry proton-rich matter. Since Mo and Ru isotopic records in solar system matter reveal the presence of more than one nucleosynthetic p -process component, these records are expected to be helpful in documenting different explosive synthesis pathways and the implied galactic evolution of p -nuclides.

Keywords

• Nucleosynthesis
• Isotopic abundances
• Meteorites