Carbon,nitrogen and sulfur in lunar fines 15012 and 15013: abundances,distributions and isotopic compositions |
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| Authors: | S Chang J Lawless M Romiez IR Kaplan C Petrowski H Sakai JW Smith |
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| Institution: | National Aeronautics and Space Administration, Ames Research Center, Moffett Field, Ca. 94035, U.S.A.;Institute of Geophysics and Planetary Physics,Los Angeles, Cal. 90024, U.S.A. |
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| Abstract: | Lunar fines 15012,16 and 15013,3 were analyzed by stepwise pyrolysis and acid hydrolysis as well as complete combustion in oxygen to determine carbon, nitrogen and sulfur. In addition, hydrogen was analysed during pyrolysis as well as during hydrolysis. In the former case, it was released by mineral grains to which it was adsorbed or from cavities within which it had been captured. Hydrogen released during hydrolysis had largely resulted from dissolution of metallic iron.By comparison of the distribution frequencies of C, N, S, H2 and Fe with 4He, considered to have arisen from solar wind contribution, it is concluded that nitrogen and hydrogen have largely a solar origin. Carbon has a significant solar contribution, and metallic iron may have resulted from solar wind interaction with ferrous minerals on the lunar surface. Sulfur probably has a predominantly lunar origin. There is no direct evidence for meteoritic contribution to these samples.Solar wind interaction also has a marked effect on the stable isotope distribution of 13C/12C, 15N/14N, and 34S/32S. In all cases, the heavy isotope was most enriched in the smallest grain-size fraction. During stepwise pyrolysis, CH4, CO2, CO and N2 were obtained at different temperatures and displayed different isotopic ratios. The carbon fraction most enriched in 13C, was CH4 liberated at 600–800°C with . Between 400 and 600°C, N2 was liberated with (δ15N ≈ +119% and at 600–800°C, N2 was liberated with relative to terrestrial atmospheric nitrogen. |
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