Effect of aluminum substitution on the reflectance spectra of hematite

Hematite and aluminous hematite were synthesized and the diffuse reflectance spectra were recorded for the region between 0.35 and 1.20 microns. Results show that the near-IR based minimum for the aluminous hematite is shifted longward by about 0.02 microns and is much more shallow. Also, the aluminous specimen is considerably more reflective shortward of approximately 0.55 microns where the ferritic specimen is strongly absorbing. This is noteworthy since the visible slope and the red shoulder are often used in the construction of false color and band ratio images

Iron mineralogy of a Hawaiian palagonitic soil with Mars-like spectral and magnetic properties

Visible and near-IR spectral data for some palagonitic soils from Mauna Kea, Hawaii, are similar to corresponding spectral data for Mars. It is important to understand the composition, distribution, and mineralogy of the ferric-bearing phases for the best spectral analogues because the correspondence in spectral properties implies that the nature of their ferric-bearing phases may be similar to those on Mars. In order to constrain interpretations of the Martian data, a variety of palagonitic soils should be studied in order to establish to what extent differences in their spectral data correspond to differences in the mineralogy of their ferric-bearing phases. Spectral (350-2100 nm), Mossbauer, magnetic, and some compositional data for one of a suite of Hawaiian palagonitic soils are presented. The soil (HWMK1) was collected below the biologically active zone from the sides of a gully cut at 9000 ft elevation on Mauna Kea. The soil was wet sieved with freon into seven size fractions less than 1 mm

Growth and Segregation of Intermenallic Phases in Zirconium Alloys

Relations between the processes of growth of intermetallic inclusions and their surface segregation in binary and ternary alloys of zirconium are presented. An increased surface concentration of iron atoms was observed, and is associated with intermetallic inclusion growth with increased annealing temperature of the deformed alloys. Modelling the asymmetric growth of these intermetallic inclusions, leading to their migration, have enabled the determination of the diffusion coefficient of iron in these intermetallics. Keywords: Zirconium alloys, Iron state, Mössbauer effec

Terrestrial impact melts as analogues for the hematization of Martian surface materials

Visible and near-IR reflectivity and Mossbauer data were obtained on powders of hydrothermally-altered impact melt sheets from West Clearwater Lake, Manicouagan, and Ries (Polsingen) impact structures. The data support previous interpretations that Martian bright regions spectra can be interpreted by a ferric-bearing phase that has a relatively featureless absorption edge together with some well-crystalline (bulk) hematite to account for the 860 nm hematite band. The data also show that bands at wavelengths longer than 900 nm, which are characteristic of Martian dark regions, occur when both hematite and pyroxene are present. It thus follows that hematization of Mars can be attributed, at least in part, to hydrothermal alterations of impact melt sheets. Impact heating could also form bulk-Hm from nanophase ferric oxides

Composition and maturity of the 60013/14 core

The 60013/14 double drive tube (62 cm deep) is one of three regolith cores taken 35-40 m apart in a triangular array on the Cayley plains at station 10' (LM/ALSEP), Apollo 16. This trio, which includes double drive tube 60009/10 (59 cm deep) and deep drill core 60001-7 (220 cm), is the only such array of cores returned from the Moon. The top 45 cm of 60013/14 is mature, as is surface reference soil 60601 taken nearby. Maturity generally decreases with depth, with soil below 45 cm being submature. The zone of lowest maturity (34 is less than or equal to I(sub s)/FeO is less than 50) extends from 46 to 58 cm depth, and corresponds to the distinct region of light-colored soil observed during core processing. In the other two cores, most of the compositional variation results from mixing between fine-grained, mature soil with 10-11 micro-g/g Sc and coarse-grained ferroan anorthosite consisting of greater than 99% plagioclase with less than 0.5 micro-g/g Sc. This is most evident in 60009/10 which contains a high abundance of plagioclase at about 54 cm depth (minimum Sc: 3-4 micro-g/g); a similar zone occurs in 60001-7 at 17-22 cm (MPU-C), although it is not as rich in plagioclase (minimum Sc: 6-7 micro-g/g). Compositional variations are less in 60013/14 than in the other two cores (range: 7.9-10.0 micro-g/g Sc), but are generally consistent with the 'plagioclase dilution' effect seen in 60009/10, i.e., most 60013/14 samples plot along the mixing line of 60009/10. However, a plagioclase component is not the cause of the lower maturity and lighter color of the unit at 46-58 cm depth in 60013/14. Many of the samples in this zone have distinctly lower Sm/Sc ratios than typical LM-area soils and plot off the mixing trend defined by 60009/10. This requires a component with moderately high Sc, but low-Sm/Sc, such as feldspathic fragmental breccia (FFB) or granulitic breccia. A component of Descartes regolith, such as occurs at North Ray Crater (NRC) and which is rich in FFB, could account for the composition of these soils (i.e., a 3:1 mixture of 60601 and NRC soil). It seems unlikely that NRC ejecta would occur half a meter deep at the LM station, thus this low-Sm/Sc component may result from an older, local crater that penetrated the Cayley surface layer and excavated underlying Descartes material, as did North Ray Crater. There is no evidence for such a unit or component in the other two cores. Soil below the light-colored unit (58-62) cm has 'typical' Sm/Sc ratios, but the lowest absolute Sc concentrations, i.e., it is compositionally equivalent to a mixture of surface soil and plagioclase such as that in ferroan anorthosite. This is the only soil that might be related to the plagioclase-rich units in the other two cores. Except for the mature soil at the top of each core and, perhaps, the plagioclase-rich layers, there is little compositional evidence for any common unit among the three cores. Soil corresponding to the mare-glass-bearing unit (MPU-B) and regolith-breccia-bearing unit (MPU-A) of 60001-7 do not occur in 60013/14 or 60009/10

Thermal and Evolved Gas Analysis of Geologic Samples Containing Organic Materials: Implications for the 2007 Mars Phoenix Scout Mission

The Thermal and Evolved Gas Analyzer (TEGA) instrument scheduled to fly onboard the 2007 Mars Phoenix Scout Mission will perform differential scanning calorimetry (DSC) and evolved gas analysis (EGA) of soil samples and ice collected from the surface and subsurface at a northern landing site on Mars. We have been developing a sample characterization data library using a laboratory DSC integrated with a quadrupole mass spectrometer to support the interpretations of TEGA data returned during the mission. The laboratory TEGA test-bed instrument has been modified to operate under conditions similar to TEGA, i.e., reduced pressure (e.g., 100 torr) and reduced carrier gas flow rates. We have previously developed a TEGA data library for a variety of volatile-bearing mineral phases, including Fe-oxyhydroxides, phyllosilicates, carbonates, and sulfates. Here we examine the thermal and evolved gas properties of samples that contain organics. One of the primary objectives of the Phoenix Scout Mission is to search for habitable zones by assessing organic or biologically interesting materials in icy soil. Nitrogen is currently the carrier gas that will be used for TEGA. In this study, we examine two possible modes of detecting organics in geologic samples; i.e., pyrolysis using N2 as the carrier gas and combustion using O2 as the carrier gas