Accretion of interplanetary dust in polar ice

Abstract

Abstract. Measurements of helium isotopes in particlesseparated from polar ice demonstrate that extraterrestrial 3He dominates the 3He flux at the GISP2 (Greenland) and Vostok

Flux and size fractionation of 3He in interplanetary dust from Antarctic ice core samples

“…years from samples from the EPICA Drønning Maud Land (EDML) ice core that are consistent with the results from Brook et al (2000) and show a relatively constant (within a factor of 2-3) flux over that time period. This paper reports additional results from larger samples of Antarctic ice, in an effort to confirm previous estimates of the 3 He flux and establish the reproducibility of the measurements.…”

“…He (n=4) on the same day. Previous measurements on unused filters revealed minimal contamination (Brook et al, 2000). The isotopic composition of only one of the two filters could be determined ( He ratios for the blank tests employing water or ice suggest contamination with 3 He enriched particles, possibly from previous samples passed through the filtration apparatus or from other aspects of sample handling in our ice core storage freezer.…”

“…Later work by Pepin et al (2000;2001) reported a similar range of ratios for individual IDPs collected in the stratosphere, but discussed puzzling occasional measurements of much higher ratios, in two cases in excess of 2000 R a (Pepin et al, 2000), which could be a signature of cosmogenic production by high energy cosmic rays. Such high ratios have not, to our knowledge, been observed in ice He ratios of 290 and 0.015 R a respectively (Brook et al, 2000), the fraction of extraterrestrial 3 He is greater than 99.99% in all 9 replicates. Therefore, no correction for terrestrial 3 He is made to the total concentrations.…”

“…Brook et al (2000) reported measurements of 3 He in particles extracted from ice cores and showed that the extraterrestrial component dominates 3 He in such samples. 3 He fluxes derived from late Holocene Greenlandic and Antarctic samples were similar to those previously reported from marine sediments, indicating that ice cores can provide a record of IDP flux.…”

3He, 20,21,22Ne, 14C, 10Be, 26Al, and 36Cl in magnetic fractions of cosmic dust from Greenland and Antarctica

“…There have also been many other studies on cosmic dust in polar ice and marine sediments, but few focused on the cosmogenic nuclides, let alone radionuclides. Brook et al (2000) studied the accretion of interplanetary dust in polar ice using 3 He. Furthermore, Farley and Patterson (1995) and Farley et al (1997) looked at long-term changes of the in-fall rate of cosmic dust in the geologic past using 3 He in ancient oceanic sediments.…”