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All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Isotopic composition of lithium, potassium, rubidium, and strontium in lunar surface material

The isotopic composition of alkali and alkaline earth elements in the Luna 16 regolith was investigated by the method of thermionic emission, without chemical separation. The isotopic composition of the lithium in two regolith samples did not differ (within the limits 0.5 percent) from the mean of the terrestrial reference standard. At the same time, the observed difference (1 percent) in the isotopic composition of lithium between the samples requires further investigation and confirmation. The isotopic compositions of K and Rb did not differ within the limits of experimental error from the isotopic composition of the reference standard.

Zaslavskiy, V. G.↗
NASA NTRS1974

Cosmic-ray exposure history at the Apollo 16 and other lunar sites - Lunar surface dynamics

Concordant Kr-81/Kr exposure ages for four station 11 breccias indicate an age of 50.3 plus or minus 0.8 m.y. for North Ray Crater. Ray structures visible from orbital photography suggest that stations 8 and 9 should contain a substantial amount of South Ray ejecta. Concordant Kr-81/Kr exposure ages at these sites indicate an age for South Ray Crater of 2.04 plus or minus 0.08 m.y. Surface effects show good general agreement with this young age, but discrepancies on a sample-by-sample basis seem to indicate that extensive presurface irradiations must have occurred.

Drozd, R. J.↗
NASA NTRS1975

Remarks on the paper 'The tidal loss of satellite-orbiting objects and its implications for the lunar surface' by Mark J. Reid

The paper by Reid (1973) suggests that masses may be stored in circumlunar orbits for long periods of time, limited only by tidal dissipation. The real loss may, however, be much faster, due to large changes in the orbit caused by the disturbing field of the earth. It is shown that the example quoted of Jupiter's satellites is inadequate to make the case for stability of such orbits.

Gold, T.↗
NASA NTRS1974

Accumulation and isotopic evolution of carbon on the lunar surface

The processes of hydrogen stripping, agglutination and impact comminution, acting upon a regolith containing both indigenous and solar wind-implanted carbon, provide a quantitative explanation for the relationship between carbon abundance and isotopic composition observed for Apollo 16 soils.

Kerridge, J. F.↗
NASA NTRS1978

Sputtering - Its relationship to isotopic fractionation on the lunar surface

Silicon, oxygen, sulfur and, possibly, potassium show systematic enrichment of heavier isotopes with increasing soil maturity, probably as a result of solar-wind sputtering, but such a pattern is not exhibited by solar wind-implanted species. Apparently sputter-erosion is not penetrating to their implantation depth, about 200 A. This suggests that sputtering on the moon is being impeded by deposition of vapor condensate following meteoritic impact. Although neither secular variation in the isotopic composition at the source of regolith carbon, probably the solar wind, nor isotopic fractionation of carbon after implantation in the regolith can be ruled out, carbon isotope systematics currently yield no evidence in support of either process.

Kerridge, J. F.↗
NASA NTRS1979

Thorium concentrations in the lunar surface. III - Deconvolution of the Apenninus region

A technique of deconvoluting orbital-gamma ray data which improves spatial resolution and contrast has been applied to Th concentrations in the Apenninus region of the moon. The highest concentration seen from orbit has been found along the northern edge of the data track at Archimedes, requiring a component more highly fractionated in KREEP than the Apollo 15 medium-K Fra Mauro basalt. The results show generally diminishing Th levels extending outward from the Imbrium Basin, and impact penetration of basalt flows in Mare Imbrium to eject sub-mare Th-rich material. The results reinforce the hypothesis that the highlands which border and underlie the western maria contain a pre-mare layer of volcanically-derived KREEP material.

Metzger, A. E.↗