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Helium and neon isotopes in stratospheric particles
Author(s) -
Nier A. O.,
Schlutter D. J.
Publication year - 1990
Publication title -
meteoritics
Language(s) - English
Resource type - Journals
eISSN - 1945-5100
pISSN - 0026-1114
DOI - 10.1111/j.1945-5100.1990.tb00710.x
Subject(s) - neon , atmosphere (unit) , interplanetary dust cloud , isotopes of neon , astrobiology , meteorite , helium , meteoroid , stratosphere , cosmic ray , isotope , particle (ecology) , isotopes of helium , earth (classical element) , atmospheric sciences , physics , solar system , geology , astrophysics , atomic physics , astronomy , nuclear physics , meteorology , argon , oceanography
— Helium and neon isotope ratios were determined for 16 interplanetary dust particles (IDPs) collected in the stratosphere. The concentration of helium observed varied greatly from particle to particle, with the highest values approaching those found for lunar surface fines and some gas‐rich meteorites. With the exception of one particle, for which the 3 He/ 4 He was (1.45 ± 0.05) × 10 −3 , the remainder of the particles had ratios falling between 1.4 and 3.1 × 10 −4 , with an average of (2.4 ± 0.3) × 10 −4 , substantially less than is associated with the solar wind or observed in average lunar fines or in lunar fines having sizes comparable to those of the IDPs studied. The average 20 Ne/ 22 Ne found was 12.0 ± 0.5. Only three reasonably reliable 21 Ne/ 22 Ne ratios could be determined, and for these the average was 0.035 ± 0.006. The isotopic ratios appear to preclude the presence of any appreciable amount of cosmic ray‐produced spallogenic products. The high 4 He concentrations observed for some of the particles, approaching those observed for lunar surface grains, suggest they were not heated to high temperatures and degassed as they descended in the earth's atmosphere. From Flynn's study of the dynamics of IDPs entering the earth's atmosphere this could mean they entered the atmosphere at relatively low velocities, and hence may be primarily of asteroidal rather than cometary origin.