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Gammage, R. B.

Publications and source records attributed to Gammage, R. B..

14 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Surface properties of a north ray crater soil /Apollo 16/

Surface properties of lunar fines sample 67481 have been investigated by measuring the adsorptions of nitrogen (at -196 C) and water (at 20 C). Characteristics of this sample are similar to those of samples from other locations on the lunar surface and include the more typical alteration reaction with adsorbed water. Although their maturities are markedly different, the surface properties of 67481 are very much like those of the more mature 63341 from the adjacent station 13. These results indicate that the surface properties of lunar soils attain an equilibrium state faster than other properties used to indicate maturity.

Holmes, H. F.↗
NASA NTRS1975

Alteration of an annealed and irradiated lunar fines sample by adsorbed water

Apollo 12 lunar fines sample 12070,403 was annealed at 1000 C and subsequently irradiated with a beam of 130 MeV Fe(9+) ions. Adsorptions of nitrogen and water were measured before and after the irradiation. Prior to the irradiation, the fines were nonporous and water had no effect on the physical characteristics of the lunar fines. In contrast, after the irradiation, the interaction with water caused an increase in the specific surface area and created a pore system. These results are definitive evidence that the interaction of water with damage tracks is the prime factor involved in the alteration of lunar fines by adsorbed water.

Holmes, H. F.↗
NASA NTRS1975

Specific surface area as a maturity index of lunar fines

Mature surface fines have an equilibrium specific surface area of about 0.6 sq m/g the equivalent mean particle size being about 3 microns. The adsorption behavior of inert gases (reversible isotherms) indicates that the particles are also nonporous in the size range of pores from 10 to 3000 A. Apparently, in mature soils there is a balance in the forces which cause fining, attrition, pore filling, and growth of lunar dust grains. Immature, lightly irradiated soils usually have coarser grains which reduce in size as aging proceeds. The specific surface area, determined by nitrogen or krypton sorption at 77 K, is a valuable index of soil maturity.

Gammage, R. B.↗
NASA NTRS1975

Interaction of gases with lunar materials

The surface properties of lunar fines were investigated. Results indicate that, for the most part, these properties are independent of the chemical composition and location of the samples on the lunar surface. The leaching of channels and pores by adsorbed water vapor is a distinguishing feature of their surface chemistry. The elements of air, if adsorbed in conjunction with water vapor or liquid water, severely impedes the leaching process. In the absence of air, liquid water is more effective than water vapor in attacking the grains. The characteristics of Apollo 17 orange fines were evaluated and compared with those of other samples. The interconnecting channels produced by water vapor adsorption were found to be wider than usual for other types of fines. Damage tracks caused by heavy cosmic ray nuclei and an unusually high halogen content might provide for stronger etching conditions upon exposure to water vapor.

Holmes, H. F.↗
NASA NTRS1975

Blocking of the water-lunar fines reaction by air and water concentration effects

The elements of air, if adsorbed in conjunction with water vapor or liquid water, are able to impede severely the attack of lunar fines. Thus is explained the stability of lunar fines in moisture laden air, and their small solubility in liquid, aerated water. In the absence of air, liquid water is more effective than water vapor in attacking the grains; the channels formed are wider and the expansion of area is greater.

Gammage, R. B.↗
NASA NTRS1975

Interaction of gases with lunar materials - Revised results for Apollo 11

The surface properties of an Apollo 11 soil sample have been reinvestigated. The present study shows that the preliminary results for this sample (Fuller et al., 1971) are in error, principally because of incorrectly applied instrumental background effects. The surface properties of these Apollo 11 fines are very similar to those of fines from the other Apollo landing sites that we have examined. On the basis of results reported to date, the surface properties (specific surface area, porosity, and reactivity with water) of lunar soil samples are, to a first approximation, independent of bulk chemical composition and location on the lunar surface. Drastic alteration of the surface characteristics of lunar fines by adsorbed water continues to be the distinguishing feature of their surface chemistry.

Holmes, H. F.↗
NASA NTRS1974

Interaction of gases with lunar materials

Quantitative efforts to assess the surface properties of lunar fines, particularly water induced porosity are discussed. Data show that: (1) changes induced in lunar fines are not visible in high energy electron micrographs, (2) scanning micrographs show no change in particle size distribution as a result of reaction with water, (3) water induced changes are internal to the particles themselves, (4) normal laboratory atmosphere blocks alteration reaction with water, and (5) surface properties of mature lunar soils appear to be almost independent of chemical composition and mineralogy, but there are some variations in their reactivity toward water.

Holmes, H. F.↗
NASA NTRS1974

Interaction of gases with lunar materials

The surface chemistry of Apollo 17 lunar fines samples 74220 (the orange soil) and 74241 (the gray control soil) has been studied by measuring the adsorption of nitrogen, argon, and oxygen (all at 77 K) and also water vapor (at 20 or 22 C). In agreement with results for samples from other missions, both samples had low initial specific surface areas, consisted of nonporous particles, and were attacked by water vapor at high relative pressure to give an increased specific surface area and create a pore system which gave rise to a capillary condensation hysteresis loop in the adsorption isotherms. In contrast to previous samples, both of the Apollo 17 soils were partially hydrophobic in their initial interaction with water vapor (both samples were completely hydrophilic after the reaction with water). The results are consistent with formation at high temperatures without subsequent exposure to significant amounts of water.

Holmes, H. F.↗
NASA NTRS1974

Some surface properties of Apollo 17 soils

The surface chemistry of Apollo 17 lunar fines samples 74220 (the orange soil) and 74241 (the gray control soil) has been studied by measuring the adsorption of nitrogen, argon, and oxygen (all at -196 C) and also water vapor (at 20 C or 22 C). In agreement with results for samples from other missions, both samples had low initial specific surface areas, consisted of nonporous particles, and were attacked by water vapor at high relative pressures to give an increased specific surface area and create a pore system which gave rise to a capillary condensation hysteresis loop in the adsorption isotherms. In contrast to previous samples, both of the Apollo 17 soils were partially hydrophobic in their initial interaction with water vapor (both samples were completely hydrophilic after the reaction with water). The results are consistent with formation at high temperatures without subsequent exposure to significant amounts of water.

Holmes, H. F.↗
NASA NTRS1973

Interaction of gases with lunar materials - Apollo 12, 14, and 16 samples

Surface properties of lunar fines samples from the Apollo 12, 14, and 16 missions have been investigated by studying the adsorption of nitrogen, argon, oxygen, carbon monoxide (all at 77 K), and water vapor (at 20 or 22 C) on the samples. Initially the samples were all nonporous and had a uniformly low specific surface area (0.3 to 0.6 sq m/g). Water interacts strongly with the surface of lunar fines, chemisorbing at low pressures followed by a massive adsorption at high pressures. Nitrogen adsorption measurements after the interaction with water showed that the surface properties had undergone a severe alteration as a result of the attack by water vapor. This alteration consisted of a marked increase in the specific surface area and the creation of a pore system. The results are interpreted on the basis of a penetration of water into the damage tracks.

Holmes, H. F.↗
NASA NTRS1971

Search for exoelectrons in Apollo 12 materials.

The search for exoelectron emission from Apollo 12 materials usually produced negative results, suggesting that the concentration of naturally occurring traps is very low. Weak exoelectron activity was found scattered inhomogeneously within a pigeonite basalt rock and in a deep core tube sample. Its erratic appearance and intensity makes any interpretation of radiation history most difficult and is attributed to the activity being carried by only a few scattered crystals. The thermally stimulated emission of exoelectrons is judged an unsuitable technique for tracing the radiation histories of these samples.

Gammage, R. B.↗