Lunar surface radioactivity: preliminary results of the apollo 15 and apollo 16 gamma-ray spectrometer experiments

Gamma-ray spectrometers on the Apollo 15 and Apollo 16 missions have been used to map the moon's radioactivity over 20 percent of its surface. The highest levels of natural radioactivity are found in Mare Imbrium and Oceanus Procellarum with contrastingly lower enhancements in the eastern maria. The ratio of potassium to uranium is higher on the far side than on the near side, although it is everywhere lower than commonly found on the earth.     

Potassium-uranium systematics of apollo 11 and apollo 12 samples: implications for lunar material history

Apollo 11 and Apollo 12 lunar rock suites differ in their potassium-uranium abundance systematics. This difference indicates that relatively little exchange of regolith material has occurred between Mare Tranquillitatis and Oceanus Procellarum. The two suites appear to have been derived from materials of identical potassium and uranium content. It appears unlikely that bulk lunar material has the ratio of potassium to uranium found in chondrites. However, systematic differences in the potassium-uranium ratio between Apollo samples and crustal rocks of the earth do not preclude a common potassium-uranium ratio for bulk earth and lunar material.     

Geologic setting of the apollo 15 samples

The samples and photographs returned from the Apollo 15 site show that Hadley Delta is largely underlain by breccias whose clasts are mainly fragments of coarse-grained feldspathic rocks and nonmare-type basalt. Conspicuous sets of lineaments, visible in surface and orbital photographs of Mount Hadley and Hadley Delta, may represent systematic layering or fracture sets. The mare surface, with regolith about 5 meters thick, is underlain by two major basalt types, at least one of which has extensive lateral continuity and is exposed in the upper wall of Hadley Rille. Gradual erosional recession of the edges and filing of the interior of the rille by talus have contributed to the present cross sectional profile.     

Geologic setting of the apollo 14 samples

The Apollo 14 lunar module landed in a region of the lunar highlands that is part of a widespread blanket of ejecta surrounding the mare Imbrium basin. Samples were collected from the regolith developed on a nearly level plain, a ridge 100 meters high, and a blocky ejecta deposit around a young crater. Large boulders in the vicinity of the landing site are coherent fragmental rocks as are some of the returned samples.     

Evidence for compounds hydrolyzable to amino acids in aqueous extracts of apollo 11 and apollo 12 lunar fines

Hydrolyzates of aqueous extracts of Apollo 11 fines, an Apollo 12 trench sample, and an Apollo 12 surface sample have been analyzed on an ultrasensitive amino acid analyzer. The total content of amino acids recovered ranged from 20 to 70 parts per billion of lunar soil. Amino acids are not recovered by the direct hydrolysis of lunar fines, presumably because of decomposition in the presence of the large excess of lunar mineral. As judged by retention time, glycine is the dominant amino acid found; alanine is secondarily present in each case in the profile. Only a few amino acids have been recorded in each analysis. The pattern is relatively consistent in the samples from the three locations; the pattern from either hydrolyzed or unhydrolyzed extracts differs markedly from that of hydrolyzed or unhydrolyzed handprints. The evidence is not consistent with contamination of the kind expected by many investigators.     

Gravity measured at the apollo 14 lading site

The gravity at the Apollo 14 landing site has been determined from the accelerometer data that were telemetered from the lunar module. The values for the lunar gravity measured at the Apollo 11, 12, and 14 sites were reduced to a common elevation and were then compared between sites. A theoretical gravity, based on the assumption of a spherical moon, was computed for each landing site and compared with the observed value. The observed gravity was also used to compute the lunar radius at each landing site.     

Tektite glass in apollo 12 sample

The glassy portion of lunar sample 12013 from Apollo 12 is chemically more like some tektites from Java than like any terrestrial igneous rock. It satisfies all the chemical criteria for a tektite. Tektites are relatively recent and acid rocks, whereas the moon is chiefly ancient and basaltic; hence, tektites are probably ejected volcanically, rather than by impact, from the moon.     

Extralunar dust in apollo cores?

Densities of nuclear tracks exceed 10(11) per square centimeter in several percent of the micrometer-size silicate grains from all depths in the 12-and 60-centimeter lunar cores. Either these grains were irradiated in space as extralunar dust or the ratio of iron to hydrogen in low-energy (about 1 million electron volts per nucleon) solar particles is orders of magnitude higher than in the photosphere.     

Origins for the near-Earth asteroids

Because of their short dynamical lifetimes, the population of near-Earth asteroids (NEAs) must be resupplied. Two sources have been hypothesized: main-belt asteroids and extinct comet nuclei. The difficulty of making physical measurements for similar sized (diameter D less than 5 kilometers) main-belt asteroids and comet nuclei has limited comparative tests for distinguishing between these alternatives. A new survey of physical properties for D < 5 kilometers main-belt asteroids reveals that their spin rate and shape distributions are similar to those of NEAs, as is fully consistent with a main-belt origin for most NEAs. Physical data on comet nuclei are limited. If the existing sample is representative of the comet population, analysis of the asteroid and comet samples constrains the fraction of comet nuclei to between 0 and 40 percent of the total NEA population.     

Alpha-particle activity of apollo 11 samples

Nine polishled thin sectionis have been exposed to nulclear track plates, three have been counted by alplia-particle spectrometry, and one has been examined by electron mocroprobe. Interpretation of the results is in a preliminary stage. Alpha track distribiutioni in the autoradiograph of a breccia forms a network that appears related to the rims of accretionary lapilli comiiposinig the breccia. Thorium in a coarse-grained crystalline rock is concenitrated in micron-sized, zirconium-rich crystals. Alplia count rates agree with what would be predicted from previously reported thorium and uranium contents of the same rocks, suggesting secular equilibriunm for the thorium and uranium decay series.     

Sound from apollo rockets in space

Low-frequency sound has been recorded on at least two occasions in Bermuda with the passage of Apollo rocket vehicles 188 kilometers aloft. The signals, which are reminiscent of N-waves from sonic booms, are (i) horizontally coherent; (ii) have extremely high (supersonic) trace velocities across the tripartite arrays; (iii) have nearly identical appearance and frequencies; (iv) have essentially identical arrival times after rocket launch; and (v) are the only coherent signals recorded over many hours. These observations seem to establish that the recorded sound comes from the rockets at high elevation. Despite this high elevation, the values of surface pressure appear to be explainable on the basis of a combination of a kinetic theory approach to shock formation in rarefied atmospheres with established gas-dynamics shock theory.     

Luminescence of apollo 11 lunar samples

Luminescence measurements were made of four lunar rocks, two terrestrial rocks (granite and gabbro), and one terrestrial mineral (willemite) by comparing the spectral curves with the curve of a barium sulfate standard. Efficiencies with 3000 angstrom excitation were < 6 x 10(-5) for the lunar samples, < 8 x 10(-5) for gabbro of very similar composition to the lunar samples, approximately 10(-4) for granite, and approximately 2 X 10(-2) for willemite. If these are typical values for other ultraviolet excitation wavelengths, the Apollo 11 site appears to contribute little to the observed lunar luminescence.     

Rare gas record in the largest apollo 15 rock

The spallation krypton data from rock chip 15555,23 indicate a wellshielded location during most of the time during which the rock was exposed to cosmic rays. A krypton-krypton exposure age of 81(+17)(-7) x 10(6) years is calculated, and the gas retention ages are estimated. No evidence for the presence of products from plutonium-244 or iodine-129 was found.     

Orthopyroxene-plagioclase fragments in the lunar soil from apollo 12

Rock fragments consisting of orthopyroxene-calcic plagioclase assemblages appear to be more common in Apollo 12 soil samples than in the breccias or soil from Apollo 11 and are mineralogically and chemically different from any of the crystalline rocks returned by either Apollo 11 or Apollo 12. Compositionally, these fragments are orthopyroxenites and feldspathic orthopyroxenites. They are probably not fragments of meteorites; other considerations point to a near-surface lunar origin.     

Spinel troctolite and anorthosite in apollo 16 samples

A spinel troctolite and an anorthosite from the Apollo 16 landing site represent contrasting types of "primitive" lunar cumulates. The two rock types probably formed from the same parent magma type, a high-alumina magnesian basalt, with the troctolite forming earlier by crystal settling, and the anorthosite later, possibly by flotation.     

Apollo 14 and apollo 16 heavy-particle dosimetry experiments

Doses of heavy particles at positions inside the command modules of Apollo missions 8, 12, 14, and 16 correlate well with the calculated effects of solar modulation of the primary cosmic radiation. Differences in doses at different stowage positions indicate that the redistribution of mass within the spacecraft could enhance safety from the biological damage that would otherwise be expected on manned, deep-space missions.