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Zhurong rover successfully landed on the southern of Utopia Planet of Mars on 15 May 2021. One laser-induced breakdown spectroscopy (LIBS) system, the main payload of the Mars Surface Composition Detector (MarSCoDe), was installed on the Zhurong rover aimed to measure the elements and their abundance in Martian regolith. Now, there are three sets of LIBS system (ChemCam, SuperCam and MarSCoDe) working on Mars at difference landing sites with diverse geologic features. For Mars exploration, cross-validation is necessary to expand the model compatibility, test data validity, and get more available data of the same type payloads. Spectral transformation approach is the first step and crucial for cross-validation of LIBS analysis model. Herein, a new 4-step spectral transformation approach was proposed to transform the LIBS spectra between three different LIBS systems (i.e., ChemCam, MarSCoDe, SDU-LIBS (recorded by self-built LIBS system)), whose data were partly different in spectral characteristics. Based on this approach, SDU-LIBS and MarSCoDe spectra data were transformed into ChemCam uniform and then the three kinds of LIBS data can have more similar spectral features and share one PLS (partial least squares) model for quantitative analysis. Our approach enables to make up the signal differences between different LIBS systems and gets acceptable quantitative analysis results of SDU-LIBS and MarSCoDe spectra using quantitative PLS model built by ChemCam calibration sample set. This work verified feasibility and availability of our approach for cross validation of different LIBS systems. Based on this method, MarSCoDe data were analyzed and got the preliminary satisfying results although no analysis model of laboratory replica payload was available under the existing conditions. [ABSTRACT FROM AUTHOR]

China's first Mars exploration mission, named Tianwen-1, landed on Mars on 15 May 2021. The Mars Surface Composition Detector (MarSCoDe) payload onboard the Zhurong rover applied the laser-induced breakdown spectroscopy (LIBS) technique to acquire chemical compositions of Martian rocks and soils. The quantitative interpretation of MarSCoDe-LIBS spectra needs to establish a LIBS spectral database that requires plenty of terrestrial geological standards. In this work, we selected 316 terrestrial standards including igneous rocks, sedimentary rocks, metamorphic rocks, and ores, whose chemical compositions, rock types, and chemical weathering characteristics were comparable to those of Martian materials from previous orbital and in situ detections. These rocks were crushed, ground, and sieved into powders less than <38 μm and pressed into pellets to minimize heterogeneity at the scale of laser spot. The chemical compositions of these standards were independently measured by X-ray fluorescence (XRF). Subsequently, the LIBS spectra of MAL standards were acquired using an established LIBS system at Shandong University (SDU-LIBS). In order to evaluate the performance of these standards in LIBS spectral interpretation, we established multivariate models using partial least squares (PLS) and least absolute shrinkage and selection (LASSO) algorithms to predict the abundance of major elements based on SDU-LIBS spectra. The root mean squared error (RMSE) values of these models are comparable to those of the published models for MarSCoDe, ChemCam, and SuperCam, suggesting these PLS and LASSO models work well. From our research, we can conclude that these 316 MAL targets are good candidates to acquire geochemistry information based on the LIBS technique. These targets could be regarded as geological standards to build a LIBS database using a prototype of MarSCoDe in the near future, which is critical to obtain accurate chemical compositions of Martian rocks and soils based on MarSCoDe-LIBS spectral data. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a powerful tool for qualitative analysis of chemical composition on planetary surface. Specifically, the quantitative compositional analysis method is a significant challenge for LIBS instrument onboard the Mars Science Laboratory (MSL) rover Curiosity ChemCam. Partial Least Squares (PLS) sub-model strategy is one of the outstanding multivariate analysis methods for calibration modeling, which is firstly developed by ChemCam science team. However, a troubling key issue is there are many parameters that need to be optimized, which increases the uncertainty of predicting outcomes and is time-consuming. In this study, an automatic parameters selection method based on Particle Swarm Optimization (PSO) tool is introduced. In the process of PSO iteration, RMSE minimization is taken as fitness, and finally the optimal sub-model parameters set is searched. In this way, the authors also get the best PLS latent variables of each sub-model by traversal method. Finally, the PSO PLS sub-model (PSO-PLS-SM) gets significant improvement in accuracy for the expanded Chemcam standards (408). And the RMSE of Si, Al, Ca, Na elements has been reduced by more than 20% relative to the conventional predictions. [ABSTRACT FROM AUTHOR]

Highlights • Addressing the open question on high ClO 4 content and high ClO 4 /Cl ratio found on Mars. • In situ sensing of free radicals generated by electrostatic discharge (ESD) in a Mars chamber. • Detection of NaClO 3 , NaClO 4 , and Na 2 CO 3 formed in NaCl through redox plasma chemistry. • Evidences of 1000 times oxidation power of ESD-electron over UVC-photon in the experimental setting. • Scaling to Mars conditions suggests an important contribution of plasma chemistry occurred in Martian dust events in perchlorate formation. Abstract We report experimental evidences to support a new formation mechanism, multiphase redox plasma chemistry, for perchlorate on Mars observed during the Phoenix mission, whose high concentrations and high ClO 4 /Cl ratio cannot be fully interpreted by photochemistry. This chemical reaction occurs between Cl-bearing minerals on the Mars surface and free radicals generated by electrostatic discharge (ESD) during Mars dust events (dust storms, dust devils, and grain saltation). We conducted simulated ESD experiments in a Mars chamber with pure CO 2 , CO 2 + H 2 O(g), and Mars Simulate Gas Mixture at Martian atmospheric pressure. We directly observed (1) the instantaneous generation of atmospheric free radicals CO + 2 , CO+, O I , H III , H II , OH, Ar I , N 2 , and N + 2 in normal glow discharge (NGD), detected by in situ plasma emission spectroscopy, and O 3 by UV and Mid-IR spectroscopy; (2) the fast transformation of NaCl to NaClO 3 and NaClO 4 detected by laser Raman spectroscopy, with oxychlorine enrichment at the sample surfaces confirmed by ion chromatography. Through two sets of experimental comparison, we found that the oxidation power of ESD-electron is three orders of magnitude higher than that of UVC-photon. We scaled our experimental results to the modeled ESD in Mars dust events and Mars surface UV radiation level, and concluded that plasma chemistry occurred during Mars dust events can be an additional important formation mechanism for the large amounts of perchlorates observed during various missions to Mars. [ABSTRACT FROM AUTHOR]

We report a study where the molecular spectral features of nine anhydrous and hydrous oxygen chlorides were analyzed both under Mars atmospheric pressure and temperature conditions in a Planetary Environment and Analysis Chamber (PEACh) and, for comparison, under ambient laboratory conditions. The goal is to understand the effect of Mars environmental conditions (mainly temperature T and CO 2 pressure P ) on their spectral features as determined by both Raman and NIR spectroscopy. These results will be used for in situ simultaneous identification of the Cl O 4 − and other intermediate oxygen chloride products generated during a dynamic electrostatic discharge (ESD) experiment. We have three major findings from the first phase of this study: (1) the ν 1 Raman peak position is the most sensitive parameter for identifying the cation speciation in perchlorates (e.g., Na, Mg, Ca), the hydration state of magnesium perchlorate (e.g., Mg(ClO 4 ) 2 ⋅ x H 2 O, x = 0 , 2 , 4 , 6 ), and the degree of oxidation of sodium oxygen chlorides (e.g., NaClO y , y = 1 , 2 , 3 , 4 ); (2) ν 1 Raman peak positions of most tested hydrous and anhydrous oxygen chlorides show no detectable changes within the tested T and P ranges relevant to the environmental conditions at Mars surface and shallow subsurface, but water Raman peaks of the hydrated salts change following T decreases; (3) under the P & T conditions relevant to current surface and shallow subsurface at Mars mid-latitude regions, both Mg(ClO 4 ) 2 ⋅ 6H 2 O and Ca(ClO 4 ) 2 ⋅ 2H 2 O are stable against dehydration, while NaClO 4 ⋅ H 2 O dehydrates, with a dehydration rate that is a function of T which was quantified by in situ NIR spectroscopy. These results are useful for the interpretations of the data from current orbital remote sensing (Vis-NIR spectra) and from future landed missions (Raman spectra). Furthermore, we have designed a set of systematic ESD experiments to be conducted in PEACh for studying the pathways and the rates of oxygen chloride generation from chloride salts, as a potential mechanism to form oxygen chlorides during Martian dust storm. The results of the current study will be used for in situ simultaneous identification of the Cl O 4 − and other intermediate oxygen chloride products generated during a dynamic ESD experiment. [ABSTRACT FROM AUTHOR]

A low-temperature microplasma generated in a dielectric barrier discharge (DBD) was used as a radiation source for the excitation of hydrogen sulfide and its determination by molecular emission spectrometry (MES). The excitation/emission chamber was enclosed to eliminate spectral interference from ambient air. The spectral emission lines of hydrogen sulfide were clearly discriminated from the background spectrum, and the emission line at 365.06 nm was selected for parameter optimization and quantitative analysis. The S 2− ions in aqueous samples were reacted with acid to generate hydrogen sulfide and then determined. The experimental parameters affecting the determination of hydrogen sulfide and S 2− were optimized. The limits of detection were 1.4 mg m −3 for H 2 S and 11.2 mg L −1 for S 2− . The repeatability of the method was satisfactory, as the RSD values were 2.3% for H 2 S and 1.8% for S 2− . The enclosed DBD-MES system was demonstrated to be a useful tool for the determination of hydrogen sulfide in gas samples and S 2− in aqueous samples. [ABSTRACT FROM AUTHOR]

A rapid method based on extractive electrospray ionization mass spectrometry (EESI-MS) has been developed for quantitative detection of trace radioactive molecular iodine-129 (129I2) in negative ion detection mode in ambient air. For actual air samples, gaseous 129I2 was completely converted into iodine-129 ions (129I−) by an excess of Na2SO3 solution. By adding excess amounts of 127I2 into the solution, the 129I− ions formed triiodide ion complexes (i.e.129+127*2I3−) which were subjected to tandem mass spectrometry experiments to exclude false positives. Quantification of iodine-129 was achieved by quantitatively measuring the characteristic fragment (i.e., 129I−) of the triiodide ion complexes. The calibration curve showed a good linearity within an relatively wide concentration range of 0.01–1000 ppb (R2 = 0.991), a limit of detection (LOD) of 4.5 ppt and a relative standard deviation (RSD) of 4.0–13.1% (n = 5). The spiking recovery of this method was found to be 82.6–110.5%. The method had also been successfully applied to detecting the trace amount of gaseous 129I2 released in a simulated nuclear leakage accident, showing a satisfactory result for the tested gaseous samples. The experimental data demonstrated that EESI-MS was a useful tool for quantitative measurement of radioactive iodine in cases such as nuclear leakage, nuclear explosions and related scenarios. [ABSTRACT FROM AUTHOR]

A simple device was constructed for the on-site sequential monitoring of emitted elemental mercury (Hg0) in coal-fired stack gas. The device integrates on-line gold amalgam preconcentration, external thermal desorption and cold excitation in an enclosed atmospheric-pressure dielectric-barrier discharge (DBD) micro-plasma chamber. The emission was monitored by using a charge coupled device spectrometer. The Hg0 emission at 253.7 nm was well separated from the emission spectra of the Ar-DBD-plasma which eliminates the spectral interferences of ambient air and gaseous inorganic small molecular pollutants in the stack gas, e.g., NOx, SO2, H2S and HCl. Quantification was based on first derivative spectra. Among the three mercury species, Hg0 is efficiently and selectively trapped on the gold amalgam at ＜220 °C, the threshold temperature for thermal desorption of the trapped Hg0 is ca. 420 °C above which the gold amalgam releases the enriched Hg0 rapidly and gives rise to a high concentration of Hg0 in the flowing Ar stream in a very short period of time which significantly improves the detection sensitivity. A linear calibration graph was achieved within 8–256 ng (the mass of enriched Hg0 on the gold trapping micro-column) with a detection limit of 2.3 ng and an RSD of 4.0% at 32 ng. A spiking recovery of 96.1% was achieved at a spiking mass level of 50 ng Hg0. For real sample analysis (stack gas from a honeycomb briquette stove), a calibration range of 2.7–60.8 ppt was achieved after 5 min preconcentration with a 0.5 L min−1 sampling flow rate. [ABSTRACT FROM AUTHOR]

Dielectric-barrier discharge (DBD) in argon as a cold source is used for the excitation of gaseous inorganic small molecules at atmospheric pressure. By choosing ammonia as a model molecule, the excitation process and the characteristics of the emission spectra are investigated. The emission spectra are recorded by designing either an open-end or an enclosed DBD excitation/emission source. The enclosed excitation mode effectively eliminates the background emissions arising from the ambient air components, especially those from nitrogen. Two emission lines attributed to the excitation of ammonia, i.e., 326.2 and 336.5 nm, are clearly isolated from the background emission spectra of argon, providing the basis for quantitative analysis. A detection limit of 0.37 ppm is achieved within a linear range of 1.2–35 ppm by monitoring at 326.2 nm. In practice, gaseous samples containing ammonia collected in a public toilet are excited in an enclosed excitation source and the emission at 326.2 nm is monitored for quantitative analysis. An ammonia concentration of 2.4 ppm is derived in the original atmospheric sample, and a spiking recovery of 94.7% is achieved at a 10 ppm ammonia level. This study shows that DBD cold excitation in combination with optical emission spectrometry (OES) offers a promising approach for the detection of ammonia pollution. [ABSTRACT FROM AUTHOR]

Abstract: In this study, diffuse reflectance mid-infrared Fourier transform spectroscopy (DRIFTS), principal components analysis (PCA) and soft independent modeling of class analogy (SIMCA) were performed on the classification of dried sea cucumber samples of the same species from various geographical areas using fingerprint region (1700–600cm−1). A set of 96 individual dried sea cucumbers (Apostichopus japonicus Selenka) grown up in four different geographical regions (Rongcheng, 16 individuals; Weihai, 20 individuals; Yantai, 40 individuals; Dalian, 20 individuals) in East China Sea were analyzed and successfully differentiated into four classes according to the distribution of geographical areas in spite of small differences in IR fingerprints. The result shows that the environmental influencing factor is the key factor contributing to the classification of sea cucumbers. And, this study also demonstrates that DRIFTS is a convenient tool for fast differentiation of seafoods from various geographical areas, such as dried sea cucumber products. [Copyright &y& Elsevier]

The development of analytical techniques suitable for sensitive, high-throughput, and nondestructive food analysis has been of increasing interest in recent years. In this study, mass-spectral fingerprints of various cheese products were rapidly recorded in the mass range of m/ z 50–300 Da without any sample pretreatment, using neutral desorption extractive electrospray ionization mass spectrometry (ND-EESI-MS) in negative ion mode. The results demonstrate that both volatile and nonvolatile analytes on greasy cheese surfaces can be directly sampled by a neutral desorption gas beam. The influence of the neutral desorption gas flow on the analyte signal was systematically investigated. Under optimized experimental conditions, reproducible results were obtained using ND-EESI-MS. Principal component analysis was applied to differentiate a total of 49 individual cheese samples (four different types), which were purchased from three different supermarkets. All samples were successfully classified according to their types; but distributors and sensory properties were not distinguishable from the spectra data. The principal components 2, 3, and 4 scores showed an excellent capacity of distinguishing types of cheese. Molecular markers of interest can be identified using tandem mass spectrometry and matching the data with those from reference compounds. The experimental data show that ND-EESI-MS is able to sensitively and directly detect analytes on greasy surfaces without chemical contamination, providing a convenient method for high-throughput food analysis with a high degree of safety. [ABSTRACT FROM AUTHOR]

Perovskite single crystals have attracted tremendous attention owing to their excellent optoelectronic properties and stability compared to typical multicrystal structures. However, the growth of high‐quality perovskite single crystals (PSCs) generally relies on temperature gradients or the introduction of additives to promote crystal growth. In this study, a vacuum evaporation crystallization technique is developed that allows PSCs to be grown under extremely stable conditions at constant temperature and without requiring additives to promote crystal growth. The new method enables the growth of PSCs of unprecedented quality, that is, MAPbBr3 single crystals that exhibit an ultranarrow full width at half maximum of 0.00701°, which surpasses that of all previously reported values. In addition, the MAPbBr3 single crystals deliver exceptional optoelectronic performance, including a long carrier lifetime of 1006 ns, an ultralow trap‐state density of 3.67 × 109 cm−3, and an ultrahigh carrier mobility of 185.86 cm2 V−1 s−1. This method is applicable to various types of PSCs, including organic–inorganic hybrids, fully inorganic structures, and low‐dimensional structures. [ABSTRACT FROM AUTHOR]

The photoinduced physics always is a critical but controversial question for the new optoelectronic materials of halide perovskites. A high‐quality MAPbBr3 single crystal is grown and the lattice expansion induced by variable power X‐ray irradiation is investigated.A photoinduced deformation measurement system utilizing the off‐axis holography technique is developed and constructed to measure and illuminate the global photo‐induced deformation of MAPbBr3. Under a 473 nm laser with a power of 50 mW, MAPbBr3 exhibits an average maximum relative deformation of 1.27 × 10−3, demonstrating its remarkable photosensitivity and robust geometric response capabilities. Digital holography reveals photostriction as a localized phenomenon, reflecting the localization effect of the photogenerated carriers. The energetic and spatial transitions of those photogenerated carriers weaken the interatomic forces and in turn straighten the Pb─Br─Pb frameworks, expanding the lattice. This geometric change and the corresponding electronic impact are verified by Raman spectra, photoluminescence measurements, and first‐principle calculations. The methods and results are significant for future research on light‐induced phenomena in perovskites and other solid materials. [ABSTRACT FROM AUTHOR]

Laboratory simulation is the only feasible way to achieve Martian environmental conditions on Earth, establishing a key link between the laboratory and Mars exploration. The mineral phases of some Martian surface materials (especially hydrated minerals), as well as their spectral features, are closely related to environmental conditions. Therefore, Martian environment simulation is necessary for Martian mineral detection and analysis. A Mars environment chamber (MEC) coupled with multiple in situ spectral sensors (VIS (visible)-NIR (near-infrared) reflectance spectroscopy, Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and UV-VIS emission spectroscopy) was developed at Shandong University at Weihai, China. This MEC is a comprehensive research platform for Martian environmental parameter simulation, regulation, and spectral data collection. Here, the structure, function and performance of the MEC and the coupled spectral sensors were systematically investigated. The spectral characteristics of some geological samples were recorded and the effect of environmental parameter variations (such as gas pressure and temperature) on the spectral features were also acquired by using the in situ spectral sensors under various simulated Martian conditions. CO2 glow discharge plasma was generated and its emission spectra were assigned. The MEC and its tested functional units worked well with good accuracy and repeatability. China is implementing its first Mars mission (Tianwen-1), which was launched on 23 July 2020 and successfully entered into a Mars orbit on 10 February 2021. Many preparatory works such as spectral databases and prediction model building are currently underway using MECs, which will help us build a solid foundation for real Martian spectral data analysis and interpretation. [ABSTRACT FROM AUTHOR]

Electrostatic discharge experiments under simulated martian atmospheric conditions indicate that atmospheric CO2 has been sequestered into carbonate by the Mars dust activities during the Amazonia era. [ABSTRACT FROM AUTHOR]

The Martian surface is oxidizing. An important oxidant, H2O2 (hydrogen peroxide), has been detected in the Martian atmosphere and is supported even below the Martian surface. H2O2 is an important target that can be used to better understand the Martian surface environment and explore extraterrestrial life and thus must be accurately detected and analyzed under Martian‐relevant temperature conditions. In this study, the Raman spectral features and the limit of detection (LOD) of H2O2 were investigated for aqueous solutions and mud mixtures. The low‐temperature spectral features and UV decomposition characteristics of H2O2 were also investigated because low temperatures and UV radiation are key environmental factors that can affect the existence of H2O2 on the Martian surface. Our results show that H2O2 has a remarkable Raman peak at 877 cm−1, which is distinguishable from H2O and other mixed minerals, making it easy to detect with an LOD of 400 ± 50 ppm in an H2O2 solution and 1666 ± 450 ppm in a kaolinite matrix (2000 ± 500 ppm in a gypsum matrix). There was no peak shift and only a certain degree of reduction in intensity for this peak in a H2O2 solution under low temperature, even for frozen H2O2. Split peaks at ~228 cm−1 appeared after freezing H2O2, whereas there was no discernable split in the peak at ~3326 cm−1 below −60°C; however, the H2O peaks were splitted. The spectral features facilitate the detection and identification of H2O2 on the Martian surface. In light of the Mars2020 and ExoMars rover missions, our study provides valuable information about the Raman detection of H2O2 on Mars. [ABSTRACT FROM AUTHOR]

In Mars exploration, rocks are good targets for compositional analysis with spectrometers. Their shape, size, and texture could provide a wealth of information for study of planetary geology. However, imitations on communications between Mars and earth lead to operations latencies and slow progress in planetary surface missions. Increasing the autonomy of rovers has become an important research direction. Autonomy is the ability to choose which scientific data to collect and which ones to send back to Earth. One of the aims is to recognize the rocks independently. The AEGIS system adopts the method of edge detection to select potential rock targets for following observation, but the type of rocks cannot be distinguished. Convolutional neural network (CNN) is getting more attention due to its performance in computer vision. However, a common issue of CNN is that it requires large amount of rock images for training, which are difficult to get. Transfer learning provides a good way to overcome the problem of lack of dataset. In this work, CNN based on vgg-16 architecture with deep transfer learning is used to automatically classify 4 groups of Martian rocks. The proposed model achieves accuracy of 100% on Martian rock images we collected from MSL Analyst 's Notebook. Moreover, a comparison between the VGG-16 transfer model and other models is made, and it can be found that the proposed model has the best performance in Martian rock classification. [ABSTRACT FROM AUTHOR]

To investigate the effect of Mn and other metal dopants on the photoelectronic performance of CsPbCl3 perovskites, we conducted a series of theoretical analyses. Our findings showed that after Mn mono-doping, the CsPbCl3 lattice contracted and the bonding strength increased, resulting in a more compact structure of the metal octahedral cage. The relaxation of the metal octahedral cage, along with the Jahn–Teller effect, results in a decrease in lattice strain between the octahedra and a reduction in the energy of the entire lattice due to the deformation of the metal octahedron. These three factors work together to reduce intrinsic defects and enhance the stability and electronic properties of CsPbCl3 perovskites. The solubility of the Mn dopant is significantly increased when co-doped with Ni, Fe, and Co dopants, as it compensates for the lattice strain induced by Mn. Doping CsPbCl3 perovskites reduces the band gap due to the decreased contributions of 3d orbitals from the dopants. Our analyses have revealed that strengthening the CsPbCl3 lattice and reducing intrinsic defects can result in improved stability and PL properties. Moreover, increasing Mn solubility and decreasing the bandgap can enhance the PLQY of orange luminescence in CsPbCl3 perovskites. These findings offer valuable insights for the development of effective strategies to enhance the photoelectronic properties of these materials. [ABSTRACT FROM AUTHOR]

• The electrostatic discharge (ESD) induced by Martian dust activities may cause the formation of color centers in NaCl. • The Cl released from NaCl crystals during Mars dust event may play an important role in perchlorate formation. • The possibility of color centers in NaCl may shed light on the detection of normally featureless chlorides on Mars. The electrostatic discharge (ESD) induced by Martian dust activities (dust storms, dust devils, and grain saltation) has been recently proposed as a powerful geological agent to modify the structure and chemistry of Martian salts. Here, we performed new experiments to simulate gas discharge in Martian dust activity in a Mars chamber to investigate the modifications of chloride exposed to a medium strength ESD process. The structural, chemical and spectral features of NaCl before and after ESD exposure were systematically characterized with multiple analysis methods. On the basis of the experimental results, we found that 1) the colorless NaCl precursor subjected to ESD exposure subsequently displayed violet/blue color, indicating the presence of color centers; 2) the color centers (V K centers and Na colloids) in NaCl cause strong and characteristic spectral features in the visible to near-infrared reflectance spectra and Raman spectra; and 3) the relative density of color centers (V K centers and Na colloids) in NaCl gradually changes with increasing ESD duration. Our results also suggest that preferential Cl was released within NaCl crystals during the ESD process, and new phases ClO 3 − , ClO 4 − , and CO 3 2 − formed, which is consistent with previous studies (Wang et al., 2020b ; Wu et al., 2018). We interpreted that preferential Cl release within NaCl crystals should be associated with the decomposition of V K centers and the sputtering process. We also proposed that the chemically active Cl species released from solid NaCl crystals is an essential part of the overall reaction pathway of perchlorate formation on Mars. Chloride exposed to the radiation environment at the Martian surface may also contain color centers, shedding light on the detection of normally featureless chlorides on Mars. [ABSTRACT FROM AUTHOR]

TlPbI 3 is a new three-dimensional layered halide perovskite with special optoelectronic properties. Simulations of unique geometric and electronic structures showed that in contrast to ordinary halide perovskites, the Tl ion orbitals significantly contribute to the bonding interactions. We simulated the low-temperature changes in the TlPbI 3 lattice by contracting the lattice constant and found that the bond angles decreased with lattice shrinkage, which reveals a significant lateral displacement between the atoms in the TlPbI 3 crystal; this leads to reinforced bonding interactions between Tl, Pb, and I ions. Stronger bonding interactions generate more dispersive band edges, thereby increasing the bandwidth and reducing the bandgap. Moreover, the enhanced dispersion of the band edges resulted in reduced effective carrier masses and anisotropic transport properties. This provides a strategy for modulating the physical performance of new perovskites. • Layered structure TlPbI 3 providing unique bonding interactions. • Simulate the low temperature induced electronic variation of TlPbI 3. • The electronic structure and effective electronic mass of TlPbI 3 are anisotropic. [ABSTRACT FROM AUTHOR]

Iron and optical maturity (OMAT) are two key geological marks of the Moon that closely related to its geochemical evolution and interactions between surface and space environment. We apply Partial Least Squares (PLS) regression to Chang'E-1 Imaging Interferometer (IIM) (32 bands between 480 and 960 nm) in mapping lunar global FeO and OMAT, and the FeO and OMAT values are derived based on reasonable spectral parameters (absorbance, band ratios, TiO 2 and maturity sensitive parameters, etc.). After been calibrated by the FeO map from Lunar Prospector Gamma-Ray Spectrometer (LP-GRS), the global FeO map derived from PLS modeling shows a quantitatively more reasonable result consistent with previous remote sensing results (LP) as well as lunar feldspathic meteorite studies and Chang'E-3 landing site. Based on the new FeO map by Chang'E-1, we discover a compositional inhomogeneity across lunar highland regions, which has not been suggested by previous datasets (e.g., Clementine UVVIS). Furthermore, we suggest that at least part of the FeO enrichments in highlands would be caused by mixing of highland and mare materials. The IIM derived OMAT map does not suggest a dichotomy of the lunar highlands and mare regions, implying the compositional differences between those two terrains have been suppressed. We further check the maturity effect for the young mare basalts (<3.0 Ga), and find that (1) the OMAT values of the young basaltic units with medium and high FeO and TiO 2 show a linear decrease with ages; (2) units with ultrahigh-FeO (>20 wt%) and ultrahigh-TiO 2 (>10 wt%) tend to have greater OMAT values and vary little with ages; (3) this may be due to the distinct optical maturity effects of ultramafic minerals (i.e., ultrahigh Fe and Ti) and/or the spectral blue shifts of abundant ilmenite. [ABSTRACT FROM AUTHOR]

Detailed chemical, structural and spectroscopic properties of jarosite solid solution minerals are key information for their potential discoveries by future remote sensing and in-situ detections on Mars. We successfully synthesized seven homogeneous K–Na jarosite solid solutions under hydrothermal conditions at 140 °C, whose phase identifications and chemical compositions are confirmed by X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). The chemical ratios of K/(K+Na) in jarosite solid solutions lead to systematic shifts of their characteristic Raman peaks ν 1 (SO 4 ) 2− (from 1006 to 1011.3 cm −1 ), ν 3 (SO 4 ) 2− (from 1100.6 to 1111.2 cm −1 ), ν 2 (SO 4 ) 2− (from 434.2 to 444.8 cm −1 ) with the increase of Na content. While the OH stretching mode decreases with even larger peak position variations (e.g., ∼3410 cm −1 peak shifts from 3410.5 to 3385.7 cm −1 ) as the K–Na jarosite solid solutions are enriched in Na content. Raman spectroscopic measurements of the seven K–Na jarosite solid solutions enabled us to build a calibration that uses Raman peak positions to estimate K–Na variation in jarosite, which is the key step for their possible applications in the future Raman applications on Mars' missions (e.g., ExoMars and Mars 2020 missions). The band assignments and compositional related variations of their XRD, near-infrared (NIR) and mid-infrared (MIR) spectra also provide informative clues for identifying the jarosite minerals and inferring their composition during martian in-situ and remote sensing measurements. [ABSTRACT FROM AUTHOR]

In this paper, we estimated the relative and absolute ages of the seven rilles (1–7) in southwest Aristarchus region in order to know when these lunar rilles formed and how they fit into lunar volcanic history. According to their superposition relationships and colors in the color-ratio composite, the geological units and features in the study area were sorted in an order from old to young: the highland materials, the glassy Fe 2+ rich pyroclastics (DMD), the rille 1, 2, 3, 5, and 7, the mature and fresh basaltic units in the east and south of the Aristarchus plateau, the rille 4 and 6, the youngest Aristarchus Craters and its ejecta deposits. Buffered Crater Counting (BCC) method provides a chance to determine ages of linear features that do not have enough surface areas for the traditional crater counting method. The BCC analysis of seven rilles had shown that five of them probably formed in the Imbrium Period and the other two formed in Eratosthenian Period. The absolute age of oldest rille is 3.77 − 0.04 + 0.03 Ga and the youngest rille׳s age is 1.49 − 0.26 + 0.26 Ga . Because their formation is interpreted to lava flowing and eroding of magma eruptions, we can see that the volcanic activities in Aristarchus region lasted for a long time from Pre-Nectarian Period (DMD materials) to Eratosthenian Period (rille 6) and weakened gradually to form small scale rilles as times went on. This may be because of the basaltic volcanic eruptions produced by heating elements in Aristarchus region to partially melt the underlying lunar mantle, which become the materials and source of these rilles. [ABSTRACT FROM AUTHOR]

The lunar global texture maps of roughness and entropy are derived at kilometer scales from Digital Elevation Models (DEMs) data obtained by Lunar Orbiter Laser Altimeter (LOLA) aboard on Lunar Reconnaissance Orbiter (LRO) spacecraft. We use statistical moments of a gray-level histogram of elevations in a neighborhood to compute the roughness and entropy value. Our texture descriptors measurements are shown in global maps at multi-sized square neighborhoods, whose length of side is 3, 5, 10, 20, 40 and 80 pixels, respectively. We found that large-scale topographical changes can only be displayed in maps with longer side of neighborhood, but the small scale global texture maps are more disorderly and unsystematic because of more complicated textures' details. Then, the frequency curves of texture maps are made out, whose shapes and distributions are changing as the spatial scales increases. Entropy frequency curve with minimum 3-pixel scale has large fluctuations and six peaks. According to this entropy curve we can classify lunar surface into maria, highlands, different parts of craters preliminarily. The most obvious textures in the middle-scale roughness and entropy maps are the two typical morphological units, smooth maria and rough highlands. For the impact crater, its roughness and entropy value are characterized by a multiple-ring structure obviously, and its different parts have different texture results. In the last, we made a 2D scatter plot between the two texture results of typical lunar maria and highlands. There are two clusters with largest dot density which are corresponded to the lunar highlands and maria separately. In the lunar mare regions (cluster A), there is a high correlation between roughness and entropy, but in the highlands (Cluster B), the entropy shows little change. This could be subjected to different geological processes of maria and highlands forming different landforms. [ABSTRACT FROM AUTHOR]

Impact-induced circular structures, known as craters, are the most obvious geographic and geomorphic features on the Moon. The studies of lunar carters' patterns and spatial distributions play an important role in understanding geologic processes of the Moon. In this paper, we proposed a method based on digital elevation model (DEM) data from lunar orbiter laser altimeter to detect the lunar craters automatically. Firstly, the DEM data of study areas are converted to a series of spatial fields having different scales, in which all overlapping depressions are detected in order (larger depressions first, then the smaller ones). Then, every depression's true boundary is calculated by Fourier expansion and shape parameters are computed. Finally, we recognize the craters from training sets manually and build a binary decision tree to automatically classify the identified depressions into craters and non-craters. In addition, our crater-detection method can provides a fast and reliable evaluation of ages of lunar geologic units, which is of great significance in lunar stratigraphy studies as well as global geologic mapping. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is a valuable tool for evaluating the geochemical characteristics of Martian rocks and was applied in the Tianwen-1 Mars exploration mission with the payload called Mars Surface Composition Detection Package (MarSCoDe). In this work, we developed a laboratory standoff LIBS system combined with a Martian simulation chamber to examine the geochemical characteristics of igneous rocks, with the intention to provide a reference and a basis for the analysis of LIBS data acquired by MarSCoDe. Fifteen igneous geological standards are selected for a preliminary LIBS spectroscopic study. Three multivariate analysis methods were applied to characterize the geochemical features of igneous standards. First, quantitative analysis was done with Partial Least Squares (PLS) and Least Absolute Shrinkage and Selection (LASSO), where the major element compositions of these samples (SiO2, Al2O3, T Fe2O3, MgO, CaO, K2O, Na2O, and TiO2) were derived. The predicted concentrations ((Fe2O3 + MgO)/SiO2, Fe2O3/MgO, Al2O3/SiO2, and (Na2O + K2O)/Al2O3) were used to identify the geochemical characteristics of igneous rocks. Also, PCA, an unsupervised multivariate method was tested to directly identify the igneous rock lithology with no prior quantification. Higher correlation (0.82–0.88) are obtained using Principal Component Analysis (PCA) scores than using predicted elemental ratios derived by PLS and LASSO, indicating that PCA is better suited to identify igneous rock lithology than via quantitative concentrations. This preliminary study, using this LIBS system, provides suitable methods for the elemental prediction and geochemical identification of martian rocks, and we will use extended geologic standards and continue to build a robust LIBS spectral library for MarSCoDe based on this LIBS system in the future. [ABSTRACT FROM AUTHOR]

Numerous occurrences of hydrated minerals (e.g., phyllosilicate, sulfate) have been found on the surface of Mars by remote sensing and in-situ exploration missions, providing strong evidence of the aqueous environment in Martian history. However, the detailed origin of these hydrated minerals is often controversial, reducing their usefulness in constraining the aqueous history of Mars. For instance, in Ophir Chasma, the origins of hydrated sulfates are debatable among hypotheses of precipitating from groundwater, paleolake, or meteoric water. In this study, we performed detailed mineralogy, morphology and stratigraphy analyses of the hydrated phases in the mineral bowl, a depression between the southern wall and mensa of Ophir Chasma, using datasets from Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), High Resolution Imaging Science Experiment (HiRISE) and High Resolution Stereo Camera (HRSC). A large number of monohydrate sulfates (MHS), polyhydrated sulfates (PHS) and some jarosite were identified in this region. Elevation of PHS-rich regions (mean elevation of −1130 ​m) is higher than those of MHS (mean value of −1401 ​m). Spectra of poly- and monohydrated sulfates mixtures were investigated in details in laboratory. Spectral features (i.e., band depth of ~1.9 ​μm, 2.1 ​μm, convexity at 2.1 ​μm and 2.4 ​μm) of sulfates mixtures changed regularly with the abundance of endmember. The linear function between the ratio of BD2100_2 to SINDEX2 and kieserite component was set up to estimate hydrated sulfates abundance. We employ the function onto CRISM data and find a coexistence of poly- and monohydrated sulfates for the formerly recognized PHS endmember, which may indicate a local dehydration/rehydration process for the sulfated minerals. Comprehensive mineralogy, topography, and stratigraphy analyses of hydrated sulfates outcrops suggest a complex formation scenario which could include surface runoff, paleolake, even aeolian erosion. • Spectral features at ~2 ​μm derived from laboratory sulfates mixtures changed regularly with the abundance of endmembers. • We calculated the abundance of hydrated sulfates in Ophir Chasma using CRISM spectral dataset. • Alternative formation scenarios of sulfates in the mineral bowl of Ophir Chasma were detailed discuss. [ABSTRACT FROM AUTHOR]

Abstract: Highly conducting AZO/Cu/AZO tri-layer films were successfully deposited on glass substrates by RF magnetron sputtering of Al-doped ZnO (AZO) and ion-beam sputtering of Cu at room temperature. The microstructures of the AZO/Cu/AZO multilayer films were studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscope (AFM). X-Ray diffraction measurements indicate that the AZO layers in the tri-layer films are polycrystalline with the ZnO hexagonal structure and have a preferred orientation with the c-axis perpendicular to the substrates. With the increase of Cu thickness, the crystallinity of AZO and Cu layers is simultaneously improved. When the Cu thickness increases from 3 to 13 nm, the resistivity decreases initially and then varies little, and the average transmittance shows a first increase and then decreases. The maximum figure of merit achieved is 1.94 × 10−2 Ω−1 for a Cu thickness of 8 nm with a resistivity of 7.92 × 10−5 Ω cm and an average transmittance of 84%. [ABSTRACT FROM AUTHOR]

Abstract: Zinc nitride films were prepared on quartz substrates by rf magnetron sputtering using pure zinc target in N2–Ar plasma. X-ray diffraction (XRD) analysis indicates that the films just after deposition are polycrystalline with a cubic structure and a preferred orientation of (400). X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of N–Zn bonds and the substitution incorporation of oxygen for nitrogen on the surface of the films. The optical band gap is calculated from the transmittance spectra of films just after deposition, and a direct band gap of 1.01±0.02eV is obtained. Room temperature PL measurement is also performed to investigate the effect of defect on the band gap and quality of the zinc nitride films. [Copyright &y& Elsevier]

Abstract: Highly conducting tri-layer films consisting of a Cu layer sandwiched between Al-doped ZnO (AZO) layers (AZO/Cu/AZO) were prepared on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of AZO and ion-beam sputtering of Cu. The tri-layer films have superior photoelectric properties compared with the bi-layer films (Cu/AZO, AZO/Cu) and single AZO films. The effect of AZO thickness on the properties of the tri-layer films was discussed. The X-ray diffraction spectra show that all films are polycrystalline consisting of a Cu layer with the cubic structure and two AZO layers with the ZnO hexagonal structure having a preferred orientation of (0 0 2) along the c-axis, and the crystallite size and the surface roughness increase simultaneously with the increase of AZO thickness. When the AZO thickness increases from 20 to 100nm, the average transmittance increases initially and then decreases. When the fixed Cu thickness is 8nm and the optimum AZO thickness of 40nm was found, a resistivity of 7.92×10−5 Ωcm and an average transmittance of 84% in the wavelength range of visible spectrum of tri-layer films have been obtained. The merit figure (F TC) for revaluing transparent electrodes can reach to 1.94×10−2 Ω−1. [Copyright &y& Elsevier]

Akaganeite has been found in Yellowknife Bay mudstones of the Gale crater by the Chemistry and Mineralogy X-ray diffraction instrument (CheMin) aboard the Curiosity rover. This phase has also been discovered in limited locations on Mars by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter. Akaganeite has also been proposed as a precursor candidate of hematite on Mars. To better constrain the stability and occurrence of akaganeite on Martian surfaces, structural and spectral modifications of akaganeite introduced by heating and desiccation were systematically investigated. We found that the phase transformation from akaganeite to hematite starts at 245 °C, which is accompanied by the removal of chloride in tunnels. We propose that geological activities (e.g., impact and volcanism on Mars) could heat the surrounding area and cause the transformation of akaganeite into hematite in Martian rocks and surface materials. Relative humidity (RH) variations result in water combination and overtone absorptions band strength changes. The CRISM spectrum of akaganeite detected in the Robert Sharp crater shows relatively weak 1.39 μm band compared to that of desiccated akaganeite under simulated Martian environments, indicating that akaganeite found on Mars could be highly desiccated. The water adsorption of akaganeite occurred when exposed to ambient laboratory conditions (RH ~65%). This suggests the water adsorption and desorption of akaganeite on Mars correspond to RH changes in a diurnal cycle. • Phase transformation from akaganeite to hematite starts at 245 °C, which is accompanied by the removal of chloride in tunnels. • Impact and volcanism activity could cause the akaganeite phase transformation on Mars. • Akaganeite on Mars surfaces is highly desiccated and could readsorb water under the conditions of high relative humidity. [ABSTRACT FROM AUTHOR]

The article focuses on findings of a study on compositions and possible sources of lunar meteorite NWA 4884. Topics include use of chemical information of lunar meteorite NWA 4884, which is a lunar regolith breccia composed of feldspathic lithology and very low titanium (VLT); TiO2 contents of mare basalts in the two possible source region; and future work related to the research, which includes analysis with Raman Microscope.