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Charette, M. P.

Publications and source records attributed to Charette, M. P..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Global color variations on the Martian surface

Spectral reflectance data from the Viking-II Orbiter vidicon cameras have provided a means of mapping and classifying Martian surface materials over about 65% of the planet. The imagery, acquired at three wavelengths, was processed to remove an average Martian photometric function; albedo maps at the three wavelengths were created. Analysis of the imagery showed that the dark region between the equator and about 30 deg S in the Martian highlands consists of ancient ridges, crater rims and rugged plateaus which are very red, and younger intercrater volcanic plains exhibiting mare ridges which are much less red. In addition probable eolian deposits were found in the intermediate and high albedo regions.

Soderblom, L. A.↗
NASA NTRS1978

Zr and Nb partition coefficients - Implications for the genesis of mare basalts, KREEP, and sea floor basalts

The distribution coefficients of Zr and Nb have been found between armalcolite, ilmenite, clinopyroxene, rutile, plagioclase, and a coexisting high-Ti mare basalt melt in the 1105-1128 C temperature range. Henry's Law is not broken over the compositional range evaluated. The distribution coefficients of clinopyroxene are strongly dependent on melt and crystal compositions. The Al2O3 activity in the melt is a strong controlling parameter. It is concluded that: (1) Apollo 11 (low K) and Apollo 17 high-Ti mare basalts may have been generated by the partial melting of an ilmenite-rich cumulate, (2) Apollo 11 (high K) basalts may have been generated by a small amount of partial melting of a more fractionated ilmenite-rich cumulate, (3) KREEP magmas may have been formed as residual melts produced by fractional crystallization of the lunar magma ocean, and (4) anomalous (type II) MOR basalts may have been generated by small degrees of partial melting of a relatively undepleted mantle with clinopyroxene remaining in the residium.

Mccallum, I. S.↗
NASA NTRS1976

Age-color relationships in the lunar highlands

The depth of the absorption feature near 1 micron in the reflectance spectra of immature lunar soils is determined primarily by the amount of pyroxene present in the soil. As a soil matures, the agglutinitic glass content increases and the Fe(2+) glass band dominates the absorption feature. An empirical relationship between the 1 micron band depth and the percentage of magnetic agglutinates, and hence maturity, is demonstrated for mature highland soils of a given composition. A similar variation of 1 micron band depth is observed in the telescopic spectra of lunar highland craters and is positively correlated with the surface maturity as determined by the small-impact erosion model of Soderblom (1970). Knowledge of both maturity and the 1 micron band depth of a lunar surface feature allows compositional information to be derived.

Charette, M. P.↗
NASA NTRS1975

Chemical fractionation of the lunar regolith by impact melting

Impact-produced agglutinitic glass in both lunar highland and mare soils is enriched in mafic elements, in potassium, phosphorus, and sulfur, and in most lithophile elements, whereas it is depleted in plagioclase components including europium. It is proposed that the chemical fractionation is the result of a multistage partial-melting mechanism that accompanies micrometeoroid impacts into soils. The process would be expected to occur on solar system bodies that have an impact-produced regolith.

Adams, J. B.↗
NASA NTRS1975

Effects of maturation on the reflectance of the lunar regolith: Apollo 16 - A case study

Soils at the Apollo 16 site become progressively darker as the percentage of glassy agglutinates increases. Magnetic separates of the agglutinate fraction of a soil are always darker than the bulk soil and are darker than the nonagglutinate fraction consisting of rock and mineral fragments. Darkening of a soil with maturity is due mainly to the increasing proportion of agglutinates. Coating of rock and mineral fragments with thin deposits of glass aids darkening in a minor way, but most of these particles eventually are destroyed by melting as the soils mature.

Adams, J. B.↗
NASA NTRS1975

Agglutinates as indicators of lunar soil maturity - The rare gas evidence at Apollo 16

The weight percent of lunar agglutinic glass (glass-welded aggregates resulting from micrometeorite impacts) in Apollo 16 bulk soils is considered with respect to quantities of trapped rare gases, e.g., He-4, Ne-20, Ar-36, Kr-84, and Xe-132, in an effort to determine the cumulative time a given soil sample has spent exposed on the lunar surface. The agglutinic glass, which reacts strongly in a magnetic field, is obtained by the standard fluid (methanol)-magnetic technique. It is noted that the absolute concentrations of trapped rare gases all show a linear relationship with increasing agglutinic glass content.

Charette, M. P.↗
NASA NTRS1975

Chemistry of agglutinate fractions in lunar soils

Agglutinates are aggregates of crystalline grains and lithic fragments bonded together by glass. It is thought that glassy agglutinates are formed at the upper surface of the lunar regolith by impact-related melting and welding of soil particles, in response to meteoroid and micrometeoroid bombardment. A description is presented of an investigation in which bulk soils were separated into 'agglutinate' and 'nonagglutinate' fractions. The obtained fractions were analyzed for major, minor, and trace elements. The obtained chemical data for agglutinate and nonagglutinate fractions of lunar soils indicate that agglutinitic glass is enriched in mafic and most lithophile elements relative to the bulk soils. A model involving preferential melting and assimilation of mesostasis material and mafic soil components is proposed to account for the observed chemical data. It is suggested that glassy agglutinates may form more readily in mafic soils than in more feldspathic ones. Such selectivity should be most effective between mare and highland soils, but may possibly operate on a more local scale.

Rhodes, J. M.↗
NASA NTRS1974

Lunar surface - Identification of the dark mantling material in the Apollo 17 soil samples

Evidence indicates that Apollo 17 sample 74001, a soil consisting of very dark spheres, is composed almost entirely of the dark mantling material that covers a large region of the southeastern boundary of Mare Serenitatis. Other Apollo 17 samples contain only a component of this material. The underlying basalt in the Taurus-Littrow valley appears to be an extension of material forming the low-albedo ring around part of Mare Serenitatis and much of the surface of Mare Tranquillitatis. The surface of this basalt region is spectrally distinct from areas with dark mantling material. These results are derived from telescopic and laboratory measurements of the optical properties of lunar soil. Digital vidicon color images are used to map the extent of these material units in the Taurus-Littrow region.

Pieters, C.↗
NASA NTRS1972

Spectrophotometry /0.3 to 1.1 micron/ of visited and proposed Apollo lunar landing sites.

The study uses information gained by analysis of the spectral properties of lunar samples in the laboratory, and telescope spectra of over 100 lunar areas, to provide information regarding the composition and mineralogy of each proposed lunar landing site. Attention is given to (1) the presence of pyroxenes which cause an absorption band near 0.95 micron in the lunar reflection spectrum, (2) the proportion of crystalline to glassy material present in the soil which is derived from the slope of the reflectivity curve between 0.4 and 0.7 micron and the strength of the 0.95 micron absorption band, and (3) the presence of Ti(3+) ions in the glasses on the lunar surface, which affects the reflection spectrum at blue and ultraviolet wavelengths.

Mccord, T. B.↗
NASA NTRS1972

Lunar spectral types.

Results of observations of the spectral reflectance properties (0.3 to 1.1 micron) of a number of lunar mare, upland, and bright crater areas with the use of ground-based telescopes. These new data are discussed in view of earlier studies in an attempt to provide a basis for more detailed interpretation. The spectral reflectivity curves (0.3 to 1.1 micron) for all lunar areas studied consist of a positive sloping continuum with a superimposed symmetric absorption band centered at 0.95 micron. Upland, mare, and bright crater materials can be identified by their spectral curves. The curves for upland and mare regions show a range of shapes from fresh, bright craters to progressively darker background material that correlates with the apparent age of the surface features. The observed upland material has uniform spectral properties, but the mare material shows some variety, probably due to Ti(3+) dispersed in lunar-soil glass. Copernicus and Aristarchus appear to have exposed upland material from beneath the mare but Kepler has not. This observation suggests that the mare is no deeper than about 15 km in the Copernicus area and about 6 km deep in the Aristarchus area, but in the Kepler area the mare must be at least about 5 km deep.

Mccord, T. B.↗