LEONIDS - DID THEY MAKE IT TO EARTH?
A. Weigel 1,2 , A. Lepland 2 , S. De 3 , K. Marti 1 , and G. Arrhenius

2 , 1 University of California, San Diego, Department of Chemistry, La Jolla CA 92093-0317, USA, 2 Scripps Institution of Oceanography, University of California, San Diego, La Jolla CA 92093-0236, USA,
3 North Cabin Road, P.O. Baruipur, 24 Parganas, West Bengal 743302, India

The Baruipur particles are porous, pale pink to gray, slags of 2-12 mm diameter. Larger particles have irregular shapes whereas smaller ones are often spherical and clustered. No fusion crust is evident on any of the particles. Analyses by SEM-EDS shows heterogeneous distribution of phases with variable proportions of Al, Ba, Si, and Fe and minor abun-dances of S, Ca, K, Ti, Mn, Ni, and Cu. X-ray dif-fraction analyses of powdered samples suggests struc-tures similar to BaFeO3 and BaAl2O4. Metallic iron droplets of 0.1-0.4 mm are present in some particles.

The isotopic abundances of noble gases were stud-ied by stepwise heating in a Ba-rich (L1) and an Al-rich (L5) fragment. Relative to air ratios (Ra) we ob-serve: 4 He/20 Ne~2.1愛a, 20 Ne/40 Ar = 1.1愛a (L1) resp. 4.7愛a (L5), 40 Ar/84 Kr = 1.25愛a (L1) resp. 1.9愛a (L5), and 84 Kr/132 Xe = 1.4愛a. 3 He/4 He in the 300蚓 step of L5 is 12.4愛a and in all other temperature steps of both samples 1.3-2.2愛a. Ne-isotopic ratios of both samples plot close to the mixing line Solar-Air. Ar isotopic ratios differ from air only in the 500蚓 step of L1 ( 40 Ar/36 Ar = 323, 38 Ar/36 Ar = 0.202). Kr-isotopic ratios are atmospheric except 78 Kr/84 Kr <1.1愛a and 80 Kr/84 Kr <2.75愛a. Xe-isotopic ratios m Xe/132 Xe rela-tive to air are plotted in Fig. 1. 124 Xe, 126 Xe, and 128 Xe in the Al-rich sample are strikingly enriched. A plot of 124 Xe/132 Xe vs. 126 Xe/132 Xe ratios of the Al-rich sample define a linear trend (r = 0.999) plotting be-tween tie-lines air-spallation Xe [2] and air-anomalous Xe [3]. In contrast to the anomalous Xe from spallation reactions in SB17 [3], we do not ob-serve any excess 131 Xe. These Xe isotopic excesses are observed in the Al-rich, but not in the Ba-rich phase. Excesses are not consistent with the Ba spallation sig-nature, but trapped Xe has atmospheric signature.

No observed meteorite fall so far has been con-nected to a cometary orbit [e.g., 4]. The non-volatile elemental abundances of comets observed in comet Halley dust and from spectral observations of ablation from cometary dust particles indicate average solar system compositions [5]. The Al-rich and Ba bearing phases of the Baruipur particles and the virtual ab-sence of Mg, and the missing fusion crust are not con-sistent with a cometary origin. For terrestrial sources, this material may represent coal combustion slag, whose precursor phases may have been fine-grained detrital aluminosilicates and biogenic barite that are common mineral impurities in coal. Apparently, the Leonid's haven't made it to Earth - yet.

Acknowledgments:
AW supported by a fellowship from the European Space Agency, AL by NASA grant NAG5-4563.

References:
[1] Bhandari et al. (1999) Current Science, 76, 619.
[2] Marti et al. (1966) Z. Natur-forsch., 21, 398.
[3] Srinivasan (1976) EPSL, 31, 129.
[4] Wetherill (1991) Comets in the Post-Halley Era, 537, Kluwer.
[5] Campins and Swindle (1998) MAPS, 33, 1201.

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