The isotopic composition and concentration of water, hydrogen, and carbon in some Apollo 15 and 16 soils and in the Apollo 17 orange soil
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Epstein, S.↗
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Nitrogen isotopes in drive tube 79002/79001 - Regolith history and nitrogen isotopic evolution in the solar wind
Variations in abundance and isotopic composition of nitrogen in 79002/79001 drive tube samples result from mixing of two soil components: one mature, N-rich, and isotopically light, resembling breccia material in the core, and the other immature, N-poor, and isotopically heavy. That these materials are common to soil at each stratigraphic level in the core suggests widespread distribution in the local regolith. Preservation of mixing correlations involving nitrogen isotopic compositions and cosmogenic N-15 concentrations suggests relatively recent mixing, perhaps in association with emplacement of the core stratigraphy. Characteristics of nitrogen release from the endmember materials, relationships between their nitrogen contents and maturity, and contrasts in their cosmogenic N-15 contents are consistent with models involving secular increase of the N-15/N-14 ratio of the solar wind.
Stone, J.↗
Nitrogen abundances and isotopic compositions in lunar samples
Isotopic analyses were carried out on soil separates as well as on bulk samples. Analyses of nitrogen fractions obtained by step-wise heating of the separates were also conducted. It was also attempted to obtain a value for the isotopic composition of indigenous lunar nitrogen from analyses of igneous rock samples. Several breccias were also analyzed for their nitrogen isotope ratios. The significance of the obtained results is discussed. Several lines of evidence point to the conclusion that the isotope ratio of the nitrogen being implanted into the lunar regolith has increased by some 15% over a period of at least 450 million years and possibly as long as 3,700 million years or more. This may be the result of changes in the nitrogen isotope ratio of the solar wind with time, or it may be due to outgassing and subsequent reimplantation of an isotopically light indigenous lunar nitrogen from the lunar interior in the early history of the moon.
Becker, R. H.↗
Lunar Science Conference, 6th, Houston, Tex., March 17-21, 1975, Proceedings. Volume 2 - Chemical and isotopic studies
The chemical compositions of lunar rocks and soils are examined, taking into account sulfur abundances and distributions in mare basalts and their source magmas, lithophile trace and major elements in Apollo 16 and 17 lunar samples, the role of vaporization processes in lunar rock formation, chemical studies of the lunar regolith with emphasis on zirconium and hafnium, a model for the lunar anorthositic gabbro, and trace-element chemistry and reducing capacity of size fractions from the Apollo 16 regolith. Other topics considered are related to lunar chronology, volatile meteoritic elements, isotopic studies, light element geochemistry, and agglutinates and regolith processes. Attention is given to meteoritic material in four terrestrial meteorite craters, the state of meteoritic material on the moon, volatile elements in Allende inclusions, oxygen isotope fractionation in Apollo 17 rocks, cosmogenic isotope production in Apollo deep-core samples, and the effects of exposure conditions on cosmic-ray records in lunar rocks.
Merrill, R. B.↗
A versatile system for biological and soil chemical tests on a planetary landing craft. I - Scientific objectives
We describe an approach for the remote detection and characterization of life in planetary soil samples. A mass spectrometer is used as the central sensor to monitor changes in the gas phase in eleven test cells filled with soil. Many biological assays, ranging from general 'in situ' assays to specific metabolic processes (such as photosynthesis, respiration, denitrification, etc.) can be performed by appropriate additions to the test cell via attached preloaded injector capsules. The system is also compatible with a number of chemical assays such as the analysis of atmospheric composition (both chemical and isotopic), the status of soil water, and the determination of compounds of carbon, nitrogen and sulfur in the soil.
Radmer, R. J.↗
A New Method for Evaluating the Carbon Isotope Characteristics of Carbonate Formed Under Cryogenic Conditions Analogous to Mars
The two upcoming robotic missions to Mars, Phoenix and MSL, will both have the capability of measuring the carbon isotopic composition of CO2 in the martian atmosphere, as well as possible CO2 trapped in carbonate minerals in the Martian soil. Results from orbital and landed missions now clearly indicate that no large scale deposits of carbonate materials exist at the surface. However, some results from orbital remote sensing have been interpreted to indicate that carbonate minerals are present as fine particles interspersed at low concentrations (approx. 2%) in the martian dust. One likely mechanism for the production of these carbonates is during the freezing of transient water near the surface. Large deposits of near surface ice and photographic evidence for flowing water on the surface suggest that transient melting and refreezing of H2O is an active process on Mars. Any exposure of these fluids to the CO2 rich atmosphere should al-low the production of HCO3- solutions. Carbonates are likely precipitates from these solutions during freezing as extensive CO2 degassing, driven by the fluid s decreasing volume, drives CO2 out. This rapid CO2 degassing increases the pH of the solution and drives carbonate precipitation. It has been shown in previous studies that this rapid CO2 degassing also results in a kinetic isotopic fractionation where the CO2 gas has a much lighter isotopic composition causing a large isotope enrichment of C-13 in the precipitated carbonate. This kinetic isotope enrichment may be very common in the current martian environment, and may be a very important factor in understanding the very high deltaC-13 values of carbonates found in the martian meteorites. However, while previous studies have succeeded in generally quantifying the magnitude of this effect, detailed studies of the consistency of this effect, and the freezing rates needed to produce it are needed to understand any carbon isotope analyses from carbonate minerals in the martian soil or dust. This study demonstrates an innovative new method for measuring the isotopic composition of gas evolved from the freezing of carbonate solutions in real time, which allows for a much clearer view of the chemical processes involved. This method now sets the stage for detailed analysis of the chemical and isotopic mechanisms that produce cryogenic carbonates.
Niles, P. B.↗
Mars Phoenix Scout Thermal Evolved Gas Analyzer (TEGA) Database: Thermal Database Development and Analysis
The Mars Phoenix Scout Lander mission in 2008 examined the history of water, searched for organics, and evaluated the potential for past/present microbial habitability in a martian arctic ice-rich soil [1]. The Thermal Evolved Gas Analyzer (TEGA) instrument measured the isotopic composition of atmospheric CO2 and detected volatile bearing mineralogy (perchlorate, carbonate, hydrated mineral phases) in the martian soil [2-7]. The TEGA data are archived at the Planetary Data System (PDS) Geosciences Node but are reported in forms that require further processing to be of use to the non-TEGA expert. The soil and blank TEGA thermal data are reported as duty cycle and must be converted to differential power (mW) to allow for enthalpy calculations of exothermic/endothermic transitions. The exothermic/endothermic temperatures are also used to determine what phases (inorganic/organic) are present in the sample. The objectives of this work are to: 1) Describe how interpretable thermal data can be created from TEGA data sets on the PDS and 2) Provide additional thermal data interpretation of two Phoenix soils (Baby Bear, Wicked Witch) and include interpretations from three unreported soils (Rosy Red 1, 2, and Burning Coals).
Sutter, B.↗
Lunar neutron stratigraphy.
Study of the isotopic composition of gadolinium and samarium in four soil and seven drill stem samples returned by the Apollo 15 mission. The results show the possibility to date sedimentary processes on the lunar surface for time scales of around 100 million years because of the particular dependence of neutron capture reactions on depth. The neutron flux has a distinct peak as a function of depth. This peak appears to lie below the level of shallow cratering for time scales of less than one billion years and consequently forms a readily identified marker layer of both depth and time.
Russ, G. P., III↗
Rubidium-strontium isotope characteristics of lunar soils.
Evaluation of K, Rb, and Sr concentrations and Sr isotopic composition for hand-picked fractions from the 175- to 1000-micron Apollo 12 fines samples 12032 and 12070 and for two less than 1-mm bulk fines samples, 14163,160 and 14259,21, from Apollo 14 which have model Rb-Sr ages close to 4.6 b.y. The Apollo 14 data indicate the presence of a radiogenic component of 4.6 b.y. model age like the Apollo 12 fines, confirming a very early geochemical differentiation of the moon. Progressively greater enrichment in K and Rb relative to the bulk fines is shown by microbreccia from both samples, ropy brown glass from 12032, and light-grey lithic fragments from 12032. Model Rb-Sr ages, based on a basaltic achondrite initial ratio, are generally close to 4.6 b.y. The microbreccias and ropy brown glass have model ages that are younger but indistinguishable from 4.6 b.y. within analytical error. Light grey lithic fragments from 12032 have a model age of 5.1 b.y. and must have had a multistage Rb/Sr evolution. The data are broadly compatible with two-component mixing models of the Apollo 12 fines. On the basis of modal composition, the microbreccia is considered the major nonbasaltic constituent.
Cliff, R. A.↗
Re-Os in Lunar Soils and Meteoritic Siderophiles on the Lunar Surface
Re-Os isotopes in lunar soils indicate approximately chondritic Re, Os, and Os isotopic compositions and substantial Re/Os fractionation, possibly due to the terminal lunar cataclysm. Additional information is contained in the original extended abstract.
Chen, J. H.↗
Pb loss from Apollo 17 glassy samples and Apollo 16 revisited
U-Th-Pb analyses of bulk samples of soil breccia 70019, when compared to KREEP data, indicate that different lunar samples are sometimes characterized by distinctly different initial Pb isotopic compositions. U-Th-Pb analyses on nonglassy samples and a glassy separate of soil breccia 70019, and bulk and agglutinate samples of soil 72701 showed that the glassy samples did lose considerable Pb relative to U less than 200 million years ago. These data support the contention of other investigators that vaporization of volatile elements owing to impact events significantly alters the chemistry of the lunar regolith. Metaclastic rock 60315 was reanalyzed and was found to be concordant at 3.93 billion years rather than slightly discordant, as was previously reported.
Nunes, P. D.↗
Nitrogen isotope systematics of two Apollo 12 soils
Soils 12023 and 12037 were analyzed for nitrogen by step-wise heating. Helium contents, Ar-40/Ar-36 ratios and spallation N-15 ages were determined in addition to nitrogen contents and isotopic compositions. The results for 12023 show it to be a typical lunar soil similar to many Apollo 16 and 17 soils in its nitrogen content and delta N-15 value, with a complex history. Soil 12037 appears to have had a simple, two-stage surface exposure history; one exposure occurring recently for about 10-20 m.y. and the other between about 3 to 4 b.y. ago. The delta N-15 value of nitrogen implanted in the earlier exposure was -125%. This nitrogen may reside in the minor components of 12037 such as the KREEP. If it should reside in the basaltic component of 12037, however, then the variation in the delta N-15 of implanted nitrogen with time probably has been more complex than previously considered.
Becker, R. H.↗
Isotopic abundances of actinide elements in Apollo 12 samples
Isotopic abundances and composition of U and Th in Apollo 12 soil and breccia samples, using mass spectroscopy
Diamond, H.↗
Noble gases in 60009-60010 drive tube samples - Trapped gases and irradiation history
Concentrations and isotopic composition of noble gases are reported for grain size separates: nine soils from the 60010-60009 double drive tube, two soils from the 60007 drill core section, and surface soil 65501. Data are reported on concentrations of solar wind gases, surface-correlated gases (involving solar wind and lunar atmosphere), surface maturity indices, cosmogenic gases, possible soil mixing, and irradiation by cosmic rays. Good correlation is found between solar wind gases in 60009 soils and such surface maturity indices as petrographic agglutinates, magnetic soil fraction, and fine-grained iron. Cosmogenic He-3, Ne-21, Ar-38, Kr-80, and Xe-126 all display close correlations in the drive tube soils.
Bogard, D. D.↗
Carbon isotopic ratios in some low-delta N-15 lunar breccias
Lunar soil breccias 10018, 79035 and 79135 were analyzed for carbon and nitrogen contents and isotopic compositions by vacuum pyrolysis, with a 500 C pre-combustion step in some cases. The combustion was used to remove carbon of terrestrial origin. Nitrogen isotopic ratios for the breccias are very low and are in agreement with results in the literature. Nitrogen yields in two cases were lower than literature values, a result attributable to heterogeneous mixing of implanted and implantation-free components in the breccias. Carbon isotopic ratios were found to be low in these breccias, even when reasonable account is taken of terrestrial carbon contamination. The results are consistent with the idea that low-delta N-15 values in lunar soils and breccias are accompanied by low-delta C-13 values, and imply that any secular variation which occurred in the delta N-15 of nitrogen implanted in lunar soils was accompanied by a similar but smaller variation in the delta C-13 of implanted carbon.
Becker, R. H.↗
Chemical composition of Apollo 14 soils 14163 and 14259
Apollo 14 lunar soils chemical element concentrations by atomic absorption spectrophotometry and isotope dilution
Nava, D. F.↗
Solar cosmic ray produced neon in lunar soils and their implication for gas-rich meteorite studies
Characteristic neon isotopic ratios, produced due to solar cosmic ray spallation (SCR) in lunar soils, are useful in deciphering and estimating the relative contributions of SCR and GCR spallation. To delineate these features, etched mineral grains from mature and immature lunar soils (14148 and 61221 respectively) were analyzed using mass spectrometry. The SF-Ne composition deduced in this work agrees with that obtained from earlier etched lunar pyroxene studies. The data points for mature soil 14148 define a line which significantly deviates from the 61221 tie line. This deviation is attributed to the presence of SCR spallation component. In this context, neon isotopic compositions (step-wise heating) in Pantar and Leighton dark portions were studied and compared with that of Fayetteville. The meteorite data points deviate significantly from the tie line joining SF-Ne and GCR (pyroxene) end points. This deviation is attributed to SCR-spallation in gas-rich chondrites.
Nautiyal, C. M.↗
Noble gas studies on regolith materials from Apollo 14 and 15.
Abundances and isotopic compositions of the five stable noble gases, He, Ne, Ar, Kr, and Xe in soils and breccia were determined. The samples investigated included material from a range of depths in a trench and a core tube. Noble gas determinations were performed in a 6-inch all-metal mass spectrometer of high sensitivity. The grain size separates and stepwise heating experimental methods used give results that supplement each other. Calculated concentrations of spallation Xe-126 in many of the fines and gas-rich breccia are presented in a table. Bulk soil samples obtained by Apollo 14 show an inverse correlation of spallation Xe-126 with grain size.
Bogard, D. D.↗