Extinct radioactivities - Trapped residuals of presolar grains

Presolar Grains from Novae

We report the discovery of five SiC grains and one graphite grain isolated from the Murchison carbonaceous meteorite whose major-element isotopic compositions indicate an origin in nova explosions. The grains are characterized by low C/C (4-9) and N/N (5-20) ratios, large excesses in Si (Si/Si ratios range to 2.1 times solar) and high Al/Al ratios. These isotopic signatures are theoretically pr...

EXTINCT Zr IN SINGLE PRESOLAR SiC GRAINS AND CONDENSATION FROM ZIRCONIUM-

DEPLETED GAS. Y. Kashiv, A. M. Davis, Z. Cai, B. Lai, S. R. Sutton, R. S. Lewis, R. Gallino and R. N. Clayton, Department of the Geophysical Sciences, Enrico Fermi Institute, Chicago Center for Cosmochemistry, Consortium for Advanced Radiation Sources, Department of Chemistry, University of Chicago, Chicago, IL 60637; Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, Dipar...

The xenon record of extinct radioactivities in the Earth.

Analyses of xenon from well gas rich in carbon dioxide reveal a large excess of radiogenic xenon-129 from the decay of extinct iodine-129. Smaller excesses observed in the heavy xenon isotopes are from fission. These results place narrow limits on any age difference between the earth and the oldest meteorites. The occurrence of excess radiogenic xenon-129 in well gas also suggests that any quan...

PRESOLAR SiC GRAINS OF TYPE C

Presolar Grains from the Qingzhen (eh3) Meteorite

A 28 g sample of the Qingzhen enstatite (EH3) chondrite was subjected to chemical and physical separation procedures to yield several grain-size residues. Ion mapping of isotopes of Si, O, and C in the ion microprobe of two size fractions (QZR4: 0.4–0.8 lm; QZR5: 0.8–2 lm) identified 55 30Si-depleted candidates out of 37,917 Si-rich grains and six 18O-depleted grains out of 54,410 oxides. Subse...