Lunar samples soils

Taylor LA, Pieters CM, Keller LP, Morris RV, McKay DS (2001) Lunar Mare Soils Space weathering and the major effect of surface-correlated nanophase Fe. J Geophys Res 106 27985-27999 Taylor PDP, Maeck R, De Bievre P (1992) Determination of the absolute isotopic composition and Atomic Weight of a reference sample of natural iron. Int J Mass Spectrom Ion Proc 121 111-125 Taylor PDP, Maeck R, Hendricks F, De Bievre P (1993) The gravimetric preparation of synthetic mixtures of iron isotopes. Int J Mass Spectrom Ion Proc 128 91-97... 

The Apollo astronauts returned 382 kg of lunar sample to Earth, and this collection was supplemented by 326 g of soil samples collected by the Soviet Luna landers. The first lunar meteorite was found in 1982 in Antarctica. Since that time, over 120 lunar meteorites representing about 60 different fall events have been collected. The total mass of these meteorites is -48 kg. About one-third of these meteorites were recovered in Antarctica by American and Japanese teams, and most of the rest were recovered in the deserts of North Africa and Oman. The lunar meteorites have significantly expanded the areas of the Moon from which we have samples. 

Another important application of this technique has been to determine the elemental composition of the lunar and Martian surfaces. Turkevich et al. (1969) constructed a rugged device to measure the backscattering of a particles from the lunar surface, which flew on three Surveyor missions in 1967-68 and yielded the first complete and accurate analysis of the lunar surface. The a particles came from a radioactive source (242Cm) that was part of the instrument package. The results of these experiments, which showed an unexpected and comparatively high abundance of Ti, were confirmed by laboratory analysis of lunar samples gathered in the Apollo missions. Since then, this technique has been used to study Martian rocks and soil. 

Cosmic-ray exposure age The retention of 38Ar by solids enables a measure of the duration for which cosmic solids have been exposed to cosmic rays. This is useful in studies of meteorites and of lunar samples. Cosmic rays striking calcium in the rocks leave fragments of 3 Ar and 38Ar in the ratio about 1.5 1, which is 38Ar-rich in comparison with solar Ar. Since the rate of arrival of cosmic rays is known, the time required for the buildup of the excess 38 Ar can be computed. For the lunar soils the... 

Ar on the Moon An early puzzle when the Apollo lunar samples were returned was the large amount of 40Ar in the lunar soil. Since the Moon has no appreciable... 

Analytical pyrolysis has been used successfiilly in many disciplines such as polymer chemistry, organic geochemistry, soil chemistry, forensic sciences, food science, environmental studies, microbiology, and extraterrestrial studies involving meteorites and lunar samples. A large number of organic substances found in nature are unsuitable for direct analysis by modern techniques such as column chromatography and mass spectrometry. This may be due to their complex structure and polar and nonvolatile character. 

Immature soil samples have S Te values that are indistinguishable from lunar rocks, whereas submature and mature soils have 5 Fe values that are greater than those of lunar rocks, and S Te values are positively correlated with Ig/FeO values (Fig. 12). Lunar regolith samples in general tend to have heavy isotopic compositions as compared to lunar rock samples, as demonstrated by isotopic analyses of O, Si, S, Mg, K, Ca, and Cd (Epstein and Taylor 1971 Clayton et al. 1974 Russell et al. 1977 Esat and Taylor 1992 Humayun and Clayton 1995 Sands et al. 2001 Thode 1976). The origin of isotopic compositions that are enriched in the heavy isotopes has been presumed to reflect sputtering by solar wind and vaporization, where preferential loss of the lighter isotope to space occurs. In contrast to previous isotopic studies, the Fe isotope compositions measured in the Lunar Soil Characterization Consortium samples can be related to a specific phase based on the positive correlation in Ig/FeO and 5 Fe values (Fig. 12). 

Figure 12. Plot of I/FeO versus 5 Fe values of lunar regolith samples from the Lunar Soil Characterization Consortium. The sub-scripted numbers after the sample numbers are the I,/FeO values measured for the <250 pm sized fraction. All analyses are for bulk samples of the different sized fractions error bars are 2a as calculated from 2 or more complete Fe isotope analyses. Modified from Wiesli et al. (2003a).

Lunar soil samples being collected by an Apollo astronaut. Figure courtesy of NASA. 

Mare basalts include lavas that erupted from fissures and pyroclastic deposits that produced glass beads. Six of the nine missions to the Moon that returned samples included basalts. The mare basalts from different sites have distinctive compositions and are classified based on their Ti02 contents, and to a lesser extent on their potassium contents (Fig. 13.3). A further subdivision is sometimes made, based on A1203 contents. Mare basalts are compositionally more diverse than their terrestrial counterparts. Volcanic glass beads, formed by fire fountains of hot lava erupting into the lunar vacuum, were found at several Apollo sites and eventually were shown to be a constituent of virtually every lunar soil. The glasses are ultramafic in composition and formed at very high temperatures. 

Figure 2.15 Ne three-isotope plot for a grain-size suite of plagioclase separates from lunar high land soil that were treated by the CSSE treatment (see text). The best fitted line through the data from all etched samples (line p) passes close to the data point GCR (galactic cosmic ray) of cosmogenic Ne. On the left side, the path of mass fractionation of SWC (solar wind composition)-Ne intersects line p at a 20Ne/22Ne ratio of -11.3, which is interpreted to represent SEP (solar energetic particle) Ne (cf. Section 2.8). Open symbols unetched sample. Solid symbols etched samples. SF Solar flare Ne. Reproduced from Signer et al. (1993).

Table 1. Results of the instrumental analysis of the lunar surface by the unmanned space probes Surveyor V, VI, and VII via the alpha-scattering technique (Turkevich et al.1 ). The data obtained on Apollo 11 soil sample 10084 are given for comparison2)...

With the exception of these small amounts of meteoritic matter, the lunar soil is derived from igneous rocks disrupted by impacts and gradually reduced to fine-grained dust. On all landing sites, the soil is much more abundant than rocks or breccias. Except on steep slopes, the whole Moon is covered with a layer dust of at least 5 m thick. The rock samples brought back are separate fragments embedded in the soil once part of the underlying bedrock, they were excavated by the impact of meteorites. 

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