2011 Vol. 22, No. 5
Partial least squares (PLS) regression was applied to the Lunar Soil Characterization Consortium (LSCC) dataset for spectral estimation of TiO2. The LSCC dataset was split into a number of subsets including the low-Ti, high-Ti, total mare soils, total highland, Apollo 16, and Apollo 14 soils to investigate the effects of interfering minerals and nonlinearity on the PLS performance. The PLS weight loading vectors were analyzed through stepwise multiple regression analysis (SMRA) to identify mineral species driving and interfering the PLS performance. PLS exhibits high performance for estimating TiO2 for the LSCC low-Ti and high-Ti mare samples and both groups analyzed together. The results suggest that while the dominant TiO2-bearing minerals are few, additional PLS factors are required to compensate the effects on the important PLS factors of minerals that are not highly corrected to TiO2, to accommodate nonlinear relationships between reflectance and TiO2, and to correct inconsistent mineral-TiO2 correlations between the high-Ti and low-Ti mare samples. Analysis of the LSCC highland soil samples indicates that the Apollo 16 soils are responsible for the large errors of TiO2 estimates when the soils are modeled with other subgroups. For the LSCC Apollo 16 samples, the dominant spectral effects of plagioclase over other dark minerals are primarily responsible for large errors of estimated TiO2. For the Apollo 14 soils, more accurate estimation for TiO2 is attributed to the positive correlation between a major TiO2-bearing component and TiO2, explaining why the Apollo 14 soils follow the regression trend when analyzed with other soils groups.
Experiments on ion implantation were performed in order to better characterize diffusion of noble gases in lunar soil. 4He+ at 50 keV with 5×1016 ions/cm2 was implanted into lunar simulants and crystal ilmenite. Helium in the samples was released by stepwise heating experiments. Based on the data, we calculated the helium diffusion coefficient and activation energy. Lunar simulants display similar 4He release patterns in curve shape as lunar soil, but release temperatures are a little lower. This is probably a consequence of long-term diffusion after implantation in lunar soil grains. Variation of activation energy was identified in the Arrhenius plots of lunar simulants and Panzhihua (攀枝花) ilmenite. We conclude that noble gas release in lunar soil cannot be described as simple thermally activated volume diffusion. Variation of diffusion parameters could be attributed to physical transformation during high temperature. Radiation damage probably impedes helium diffusion. However, bubble radius growth during heating does not correlate with activation energy variation. Activation energy of Panzhihua ilmenite is 57.935 kJ/mol. The experimental results confirm that ilmenite is more retentive for noble gas than other lunar materials.
A systematic spectroscopic study including Raman, Mid-IR, NIR, and VIS-NIR, is used to investigate four endmember lunar soils. Apollo soils (< 45 μm) 14163, 15271, 67511, and 71501 were selected as endmembers to study, based on their soil chemistry, maturity against space weathering, and the sampling locations. These endmembers include an anorthositic highlands soil (67511), a low-Ti basaltic soil (15271), a high-Ti basaltic soil (71501), and a mafic, KREEPy, impact-melt-rich soil (14163). We used a laser Raman point-counting procedure to derive mineral modes of the soils and the compositional distributions of major mineral phases, which in turn reflect characteristics of the main source materials for these soils. The Mid-IR, NIR, and VIS-NIR spectroscopic properties also yield distinct information on mineralogy, geochemistry, and maturity among the four soils. Knowledge of the mineralogy resulting from the Raman point-counting procedure corresponds well with bulk mineralogy and soil properties based on Mid-IR, NIR, and VIS-NIR spectroscopy. The future synergistic application of these spectroscopy methods on the Moon will provide a linkage between the results from in situ surface exploration and those from orbital remote-sensing observations.
In order to derive the distribution of olivine and pyroxene in Crater Copernicus, we compute two band ratios (950/750 and 2 000/1 500 nm), percent content of elements (Al%, Ca%, Mg%, FeO%) and maturity (Is/FeO) based on Clementine UVVIS and NIR image data. The central peaks of Copernicus, which are known to be olivine-rich or pyroxene-rich, are chosen as "ground truth" and ROIs used to derive the distribution of olivine and pyroxene with a decision tree and spectral angle mapper (SAM). Additionally, we compared previous works and the extraction results coming from the decision tree and the SAM method. The extraction of olivine by both decision tree and SAM agrees well with the previous works' descriptions, and the result by SAM is more accurate than that by decision tree because spectral features are fully used in SAM. For pyroxene extraction, there is a difference between SAM and the decision tree; one of the reasons is that the decision tree does not fully take advantage of spectral features but is only based on statistics. SAM uses band indices that can be easily extended to other areas on the Moon.
Marius Hills is a volcanic plateau on the nearside of the Moon. It is of great interest for its high concentration of volcanic features, including domes, cones, ridges, and rilles. However, the morphological and chronological characteristics of this plateau were not well studied due to the low resolution of early mission data. This study describes the detailed morphology of the volcanic features using the latest high spatial resolution images of the Terrain Camera (TC) onboard Selene-1 (10 m/pix) and Narrow Angle Camera (NAC) onboard the Lunar Reconnaissance Orbiter (LRO) (0.5 m/pix). We report here some new structures such as skylights and remnants of lava tubes. We have divided spectrally homogenous areas with Clementine UVVIS data and did crater size frequency distribution (CSFD) measurements with Lunar Orbiter (LO) IV and TC images in every spectral unit. We first report absolute model ages of 1.10 Ga for Marius basalt 1, 1.49 Ga for Flamsteed basalt, and 1.46 Ga for Schiaparelli Basalt. In addition, we have identified several younger lava events: they are Marius basalt 2 (814 Ma), medium to low titanium basalt (949 Ma), and undifferentiated medium titanium basalt (687 Ma). Finally, we propose a mantle plume scenario for the formation of Marius Hills, which could solve the inconsistency of previous models.
A novel automatic seamless stitching method is presented. Compared to the traditional method, it can speed the processing and minimize the utilization of human resources to produce global lunar map. Meanwhile, a new global image map of the Moon with spatial resolution of ~120 m has been completed by the proposed method from Chang'E-1 CCD image data.
Pasveh gabbros are mafic component of a plutonic complex in the northwest Sanandaj-Sirjan Zone. These cumulative rocks are composed of plagioclase and calcic clinopyroxene (Cpx), which yield unusually high CaO (> 19 wt.%) in whole-rock chemistry. Petrographical and geochemical data suggest that Pasveh gabbros can be divided into two groups: free scapolite and scapolite-bearing gabbros. The second group has higher Na2O, K2O, and P2O5 relative to free scapolite ones and is enriched in LIL (large ion lithophile) and HFS (high field strength) elements. Two stages of metasomatism affected the primary composition of mafic rocks. Firstly, high temperature reaction caused to invert primary high Ti clinopyroxene to low Ti clinopyroxene+high Ti amphibole. This reaction was extensive and included all gabbroic samples. Hydrothermal fluids involved in this process can be derived from dehydration reactions of country rocks or from other magmas incorporated in the formation of Pasveh complex pluton. The second metasomatic stage relates to scapolitization of limited parts of gabbroic rocks. An external saline fluid, which is composed of major NaCl and minor KCl and P2O5 components, impacted locally on Pasveh gabbros and formed the second metasomatic stage. Possible sources of Na and Cl are primary evaporites or brines, which were present in the host sediments of the gabbros. The carbonate-free nature of these hydrothermal fluids suggests that hydrothermal fluids responsible for the formation of scapolite in Pasveh gabbros are derived from marine evaporitic parentage.
Underpressured reservoirs are widespread in the Huatugou (花土沟) oilfield of the western uplift in Qaidam basin, western China. At depths between 462 and 1 248 m, the pressure of Neogene reservoirs in the Huatugou oilfield is only about 40% to 80% of hydrostatic pressure. Based on a study of the geological characteristics of these underpressured reservoirs, this work used fluid inclusion analysis and numerical simulation to investigate the mechanism creating these abnormal pressures and to evaluate the characteristics of the hydrocarbon distribution. The results show that the underpressured reservoirs are all well-sealed by undercompacted and thick mudrocks. The large-scale tectonic uplift in the late Himalayan plays an important role in the generation of underpressure in the Huatugou oilfield. At the beginning of this movement, the field was overpressured due to episodic petroleum accumulation. Later, structural uplift and erosion led to porous rebound and a temperature decrease, which produced the underpressure.
Using 1 Hz sampling records at one superconducting gravimeter (SG) station and 11 broadband seismometer stations, we found anomalous signals prior to the 2008 Wenchuan (汶川) earthquake event. The tides are removed from the original SG records to obtain the gravity residuals. Applying the Hilbert-Huang transform (HHT) and the wavelet analysis to the SG gravity residuals leads to time-frequency spectra, which suggests that there is an anomalous signal series around 39 h prior to the event. The period and the magnitude of the anomalous signal series are about 8 s and 3×10−8 m/s2 (3 μGal), respectively. In another aspect, applying HHT analysis technique to 11 records at broadband seismometer stations shows that most of them contain anomalous signals prior to the Wenchuan event, and the marginal spectra of 8 inland stations show an apparent characteristic of double peaks in anomalous days compared to the only one peak of the marginal spectra in quiet days. Preliminary investigations suggest that the anomalous signals prior to the earthquake are closely related to the low-frequency earthquake (LFE). We concluded that the SG data as well as the broadband seismometers records might be significant information sources in detecting the anomalous signals prior to large earthquakes.
In order to ensure safe drilling in deep water and marine gas hydrate bearing sediments, the needed characteristics of drilling fluid system were analyzed. Moreover, the effect of different agents on hydrate formation and the low-temperature rheology of designed polyalcohol drilling fluid were tested, respectively. The results show that clay can promote gas hydrate growth, while modified starch and polyalcohol can inhibit hydrate formation to some extent, and PVP K90 has a good performance on hydrate inhibition. The influence of clay on low-temperature rheology of polyglycols drilling fluid is notable. Therefore, the clay-free polyalcohol drilling fluid is suitable for deep water and marine gas hydrate drilling under optimal conditions.
In order to investigate the impact of urbanization and industrialization on surface water quality, a pilot study of Panzhihua (攀枝花) mining town was carried out. The urbanization of Panzhihua region was dominated by industry development and population growth. The level of urbanization showed that it was 18.44% in 1965, and reached 45.99% in 1983. Then, it reached 53.71% in 2005, so the urbanization process was very rapid in Panzhihua region. In the process of industrialization, the level of industrialization was fluctuated at around 70% from 1965 to 2005, which was influenced by mining, extracting, and smelting production. In the processes of urbanization, population growth caused an increase in life pollution sources, and an amount of effluents bearing coliform, COD (chemical oxygen demand), NH4+-N, and BOD5 (five-day biological oxygen demand) were released into Jinsha (金沙) River, which could cause decline in the surface water quality. While in the processes of industrialization (especially industrial scale expansion), more effluent bearing heavy metals could cause degradation of surface water quality. Thus, the measures, such as adjusting industry structure, optimizing the cleaning technology, and controlling pollution sources, should be enhanced to alleviate the current state of water quality exacerbation.
The microbial molecular ecology techniques, which were developed on the basis of molecular, were applied in studying the bacteria in Constructed Rapid Infiltration (CRI) system. These techniques are very efficient in better describing the bacterial diversity, microbial community distribution, and relations between microbial group structure and nitrogen contamination through the analysis of microbial nucleic acid sequence fragment in CRI. The results further revealed the removal mechanism of contamination, which is essential for the improvement of wastewater treatment in CRI.