Search for solar-type nitrogen in the gas-rich Pesyanoe meteorite

Abstract

An initial study carried out to isolate and characterize solar wind N in the dark portion of the enstatite achondrite Pesyanoe is presented. Nitrogen isotopic data obtained from a stepwise gas release of two grain- size fractions of the gas-rich meteorite are given. It is determined that more than one trapped N component is present and that indigenous N is released above 1000 C with an isotopic signature of delta N−15 = −33 per mil. A heavy N component is detected at 700-800 C, and coincides with a major release of solar-type noble gases. A lower limit of delta N−15 = −6 per mil is defined by the isotopic shifts at this range of temperature for the second element of a two-component mixture, whereas the delta N−15 signature depends on the adopted elemental abundances for a solar-type component. It is pointed out that the timing of solar wind loading of Pesyanoe is only constrained to correspond to the cosmic ray exposure age (less than 60 Ma), although it is generally assumed that this irradiation took place during an early stage. (L.K.S.)