Phosphorus is an important minor element on the Moon. It is moderately volatile and is found as both phosphates and phosphides in lunar material. The phosphides, such as schreibersite, are common to impact breccias at all Apollo sites. The origin of this schreibersite has been proposed to be a meteoritic contaminant, or alternatively produced in situ by reduction on the lunar surface. I propose that schreibersite and other siderophilic P phases have an origin from impact volatilization of phosphates at the lunar oxygen fugacity, followed by reaction of P gases with metal to form metal phosphides. This pathway is broadly consistent with the composition and structure of metal grains, as well as the native oxygen fugacity of the lunar surface. Additionally, this pathway suggests schreibersite is widespread across the lunar surface and likely on other planetary bodies, and hence may serve as a good P source for in situ resource utilization. (c) 2014 Elsevier Inc. All rights reserved.

Simultaneous static-mode mass spectrometric measurements of nitrogen, carbon, helium, neon, and argon extracted from the same aliquot of sample by high-resolution stepped combustion have been made for a suite of six lunar basalts. Collecting abundance and isotopic data for several elements simultaneously from the same sample aliquot enables more detailed identification of different volatile components present in the basalts by comparing release patterns for volatiles across a range of temperature steps. This approach has yielded new data, from which new insights can be gained regarding the indigenous volatile inventory of the Moon. By taking into account N and C data for mid-temperature steps, unaffected by terrestrial contamination or cosmogenic additions, it is possible to determine the indigenous N and C signatures of the lunar basalts. With an average delta N-15 value of around +0.35 parts per thousand, the indigenous N component seen in these samples is similar within error to other (albeit limited in number) isotopic measurements of indigenous lunar N. Average C/N ratios for indigenous volatiles in these six basalt samples are much lower than those of the terrestrial depleted mantle, or bulk silicate Earth, possibly suggesting much less C in the lunar interior, relative to N, than on Earth. Cosmogenic isotopes in these samples are well-correlated with published sample exposure ages, and record the rate of in situ production of spallogenic volatiles within material on the lunar surface. (c) 2014 The Authors. Published by Elsevier Inc.

We report new nitrogen and argon isotope and abundance results for single breccia clasts and agglutinates from four different sections of the Luna 24 drill core in order to re-evaluate the provenance of N trapped in lunar regolith, and to place limits on the flux of planetary material to the Moon's surface. Single Luna 24 grains with 40Ar/Ar-36 ratios <1 show delta N-15 values between -54.57. and +123.3 parts per thousand relative to terrestrial atmosphere. Thus, low-antiquity lunar soils record both positive and negative delta N-15 signatures, and the secular increase of the delta N-15 value previously postulated by Kerridge (Kerridge, J.F. [1975]. Science 188(4184), 162-164. doi:10.1126/science.188.4184.162) is no longer apparent when the Luna and Apollo data are combined. Instead, the N isotope signatures, corrected for cosmogenic N-15, are consistent with binary mixing between isotopically light solar wind (SW) N and a planetary N component with a delta N-15 value of +100%, to +160%,. The lower delta N-15 values of Luna 24 grains compared to Apollo samples reflect a higher relative proportion of solar N, resulting from the higher SW fluence in the region of Mare Crisium compared to the central near side of the Moon. Carbonaceous chondrite-like micro-impactors match well the required isotope characteristics of the non-solar N component trapped in low-antiquity lunar regolith. In contrast, a possible cometary contribution to the non-solar N flux is constrained to be <= 3-13%. Based on the mixing ratio of SW to planetary N obtained for recently exposed lunar soils, we estimate the flux of micro-impactors to be (2.2-5.7) x 10(3) tons yr(-1) at the surface of the Moon. Our estimate for Luna 24 agrees well with that for young Apollo regolith, indicating that the supply of planetary material does not depend on lunar location. Thus, the continuous influx of water-bearing cosmic dust may have represented an important source of water for the lunar surface over the past similar to 1 Ga, provided that water removal rates (i.e., by meteorite impacts, photodissociation, and sputtering) do not exceed accumulation rates. (C) 2011 Elsevier Inc. All rights reserved.