Presolar Grains From Novae: Evidence From Neon and Helium Isotopes in Comet Dust Collections

Abstract

Presolar grains in meteorites and interplanetary dust particles carry non-solar isotopic signatures pointing to origins in supernovae, giant stars, and possibly other stellar sources. There have been suggestions that some of these grains condensed in the ejecta of classical nova outbursts, but the evidence is ambiguous. We report neon and helium compositions in particles captured on stratospheric collectors flown to sample materials from comets 26P/Grigg-Skjellerup and 55P/Tempel-Tuttle that point to condensation of their gas carriers in the ejecta of a neon (ONe) nova. The absence of detectable 3 He in these particles indicates space exposure to solar wind irradiation of a few decades at most, consistent with origins in cometary dust streams. Measured

Helium, neon, and argon composition of the solar wind as recorded in gold and other Genesis collector materials

“…This accumulation procedure, in which He and Ne released in heating steps prior to interruption are stored in the spectrometer without immediate analysis, could in principle compromise extrapolations to spectrometer inlet times and calculations of blank and memory corrections. However no such effects were found in a detailed examination of the procedure (Pepin et al, 2011).…”

Helium and neon in comet 81P/Wild 2 samples from the NASA Stardust mission

“…Its memory‐corrected compositional ranges trend toward those measured in anomalous IDPs from the 26P/Grigg‐Skjellerup and 55P/Tempel‐Tuttle comet collections, attributed to origin in ejecta of a neon (ONe) nova (see section V.A.3; Pepin et al. ).…”

“…IDPs show a wide range of 4 He/ 20 Ne [~ (0–250)], with 20 Ne/ 22 Ne ratios typically between 10 and 14 (Pepin et al. ). This is in sharp contrast to anomalous IDPs (Pepin et al.…”

“…Blank 2 had an unusually high, and sample BD1 an unusually low, 4 He/ 20 Ne ratio, but other samples fall within the typical IDP range (Pepin et al. ).…”

“…A more detailed description of the experimental procedure and data acquisition protocol is described in Pepin et al. ()—in particular, details of how the low‐abundance 3 He and 21 Ne isotopes were measured and analyzed.…”