Lonar Crater Research Articles

Quality Assessment of Water of the Lonar Crater in Rainy Season

Lonar crater is the natural water body and unique ecosystem with its own feature in Buldhana district of Maharashtra state in India. It is the crater formed by hyper velocity two million-ton meteorite the impacted on the earth. It was formed by hyper velocity meteorite impact and situated in the basaltic terrine. Lonar crater is the third largest natural saline-water lake in the world. The crater possesses the smallest forest sanctuary with great biological diversity. The crater is 150 meter in depth and is absolutely confined from all sides by the walls of the crater. There is not a single channel of water draining away from it, there by leaving the crater waters stagnant from thousands of years. Now a day’s many human activities create the pollution in and around the water body, due to which natural status of this crater may come in the danger zone of water pollution. In this connection the study were carried out in which water of Lonar crater were collected and analyzed for their physico-chemical characteristics in rainy season to report the status of water quality of Lonar crater.

Isolation and Molecular Characterization of Chromium Reducing Haloalkaliphilic Bacteria from Alkaline Lonar Lake

Heavy metals generated mainly through many anthropogenic processes, and some natural processes have been a great environmental challenge and continued to be the concern of many researchers and environmental scientists. This is mainly due to their highest toxicity even at a minimum concentration as they are nonbiodegradable and can persist in the aquatic and terrestrial environments for long periods. Chromium ions, especially hexavalent ions (Cr(VI)) generated through the different industrial process such as tanneries, metallurgical, petroleum, refractory, oil well drilling, electroplating, mining, textile, pulp and paper industries, are among toxic heavy metal ions, which pose toxic effects to human, plants, microorganisms, and aquatic lives.The present study deals with isolation and molecular characterization of bacteria from alkaline lonar crater, having ability to survive and remediate the chromium. In the present study, 26 bacterial isolates were obtained from twelve samples of water, matt and sediment collected from Lonar Lake. Among these isolates, a well characterized isolate ASJ 21 was subjected for molecular characterization on the basis of 16S rRNA gene sequencing. On the basis of 16S rRNA gene sequencing, isolate ASJ 21 was identified as Lysinibacillus mangiferihumi. The chromium remediation ability of Lysinibacillus mangiferihumi was studied spectrophotometrically by using Di-phenyl carbazide assay and the study revealed that the isolate Lysinibacillus mangiferihumi reduced 88% of chromium and rate reduction of chromium was found to be 0.916 µg/mL after 96h of incubation period, showing the ability of microorganisms to tolerate the chromium concentration at alkaline pH and potential to remediate and detoxify hexavalent Chromium (VI) to trivalent Chromium (III) as well.

Linking impact melt redox with crustal weathering regime

Impact melting and outgassing of impact melts were important processes shaping the crust and atmosphere of early Earth and Mars. The redox state of impact melts influences the gases they release, but the controls on impact melt redox are not well understood. Here, we present Fe micro−X-ray absorption near edge structure (μ-XANES) measurements of a suite of impact melt glasses from Lonar crater, India. As an impact into continental flood basalts, Lonar crater is an ideal analog for impacts into basaltic crust on early Earth and Mars. The Fe-μ-XANES technique permits robust characterization of the Fe3+/ΣFe ratio and therefore redox conditions in Lonar glasses. We found a range in Fe3+/ΣFe of 0.21−0.49 among Lonar glasses, including substantial intraclast variations. We conclude that a primary factor driving these variations was pre-impact oxidative weathering of target rocks. The coupling between crustal weathering regime and speciation of gases released from impact melts implies that impact melt outgassing could act as a feedback mechanism to reinforce prevailing surface redox conditions.

Native Nickel–Iron Metals from Lonar Crater Impactites (India) and Regolith of the Moon

The Lonar crater (India) is the best preserved and most studied on Earth, formed in basalts, which makes it possible to conduct a comparative study with impact transformations of mineral matter on the Moon and other planets of the Solar System. Comparative studies have shown that impactor material, both on the Earth and on the Moon, is present in impactites not only in a geochemically dispersed form, as previously thought, but also in the form of individual submicron particles distributed in the molten target material. These are particles of native nickel, taenite, and high-nickel kamacite, which, apparently, are the transformed material of the impactor. High-nickel submicron metal inclusions are widespread in the impactites of the Lonar crater, as they were found in all studied preparations made from materials collected from different points along the rim of the crater. The high-nickel particles found in this study are an additional argument in favor of the previously stated assumption about the chondrite type of impactor.

Estimating the Net Magnetic Moment of Geological Samples From Planar Field Maps Using Multipoles

AbstractRecent advances in magnetic microscopy have enabled studies of geological samples whose weak and spatially nonuniform magnetizations were previously inaccessible to standard magnetometry techniques. A quantity of central importance is the net magnetic moment, which reflects the mean direction and the intensity of the magnetization states of numerous ferromagnetic crystals within a certain volume. The planar arrangement of typical magnetic microscopy measurements, which originates from measuring the field immediately above the polished surface of a sample to maximize sensitivity and spatial resolution, makes estimating net moments considerably more challenging than with spherically distributed data. In particular, spatially extended and nonuniform magnetization distributions often cannot be adequately approximated by a single magnetic dipole. To address this limitation, we developed a multipole fitting technique that can accurately estimate net moment using spherical harmonic multipole expansions computed from planar data. Given that the optimal location for the origin of such expansions is unknown beforehand and generally unconstrained, regularization of this inverse problem is critical for obtaining accurate moment estimates from noisy experimental magnetic data. We characterized the performance of the technique using synthetic sources under different conditions (noiseless data, data corrupted with simulated white noise, and data corrupted with measured instrument noise). We then validated and demonstrated the technique using superconducting quantum interference device microscopy measurements of impact melt spherules from Lonar crater, India and dusty olivine chondrules from the CO chondrite meteorite Dominion Range 08006.

3-D geometry of the Lonar impact crater, India, imaged from cultural seismic noise

SUMMARY The Lonar impact crater in the Deccan Volcanic Province of India is an excellent analogue for impact-induced structures on the Moon and other terrestrial planets. We present a detailed architecture of the crater using a high-resolution 3-D seismic velocity image to a depth of 1.5 km through the inversion of high-frequency ambient noise data recorded over 20 broad-band seismographs operating around the crater. The ambient noise waveform is dominated by cultural noise in the 1–10 Hz band. The shear wave velocity (Vs) model is created from Rayleigh wave group velocity data with a horizontal resolution of 0.5–1 km in the period range of 0.1–1.2 s. A key feature of the model is a velocity reduction of 10–15 per cent below the crater compared to outside the ejecta zone. The low-velocity zone below the crater is nearly circular and extends to a depth of ∼500 m. This estimated crater's depth is consistent with global depth–diameter scaling relations for simple craters. The basement, with a Vs of more than 2.5 km s−1, lies beneath the Deccan basalt, which has a Vs of ∼2.4 km s−1. These results are consistent with laboratory-measured data from the Lonar crater and borehole data in the western Deccan trap. This study opens a new window for exploring impact craters and sub-basalt structures using high-frequency ambient noise tomography.

Rock magnetism of ejected basaltic boulders from Lonar crater, India: Implications for the existence of a short‐lived impact‐generated weak magnetic field

AbstractThe continuous ejecta deposit around the rim of Lonar impact crater, central India, contains angular basaltic boulders of size ≤5 m. These boulders experienced varying level of shock between 2–30 GPa due to impact, as indicated by the extreme fracturing of these basaltic boulders, fragmentation of plagioclase and titanomagnetite constituents of these ejected boulders, and the presence of maskelynite in them. We measure some rock magnetic properties, e.g., NRM/χ (natural remanent magnetization [NRM]/bulk magnetic susceptibility [χ]), REM (=NRM/saturation isothermal remanent magnetization [SIRM] ratio expressed in %), and anisotropy of magnetic susceptibility (AMS) on 53 subsamples from 18 oriented drill cores of the shocked ejected basaltic boulders from the eastern half of ejecta deposit in the present study. The measured data are similar in many respects to our previous observations on Lonar crater rim shocked basalts (Arif et al. 2012b). For example, a small population of the ejected basaltic boulder samples show very high NRM/χ (between 378 and 989 Am−1; n = 7) and REM (between 1.5 and 7%; n = 4) and the AMS axes of these ejected basaltic boulders show triaxial distributions in stereographic projections. Moreover, some of the ejected basaltic boulders show higher values of squareness ratio (Mrs/Ms) and median destructive field (MDF) suggesting permanent changes in the intrinsic magnetic properties due to impact shock pressure. In stereographic plot, the high coercivity and high temperature (HC_HT) magnetization component of these ejected basaltic boulders are distributed in discrete clusters on the periphery of a small enveloping circle whose center (D = 108.0°, I = +69.2°) lies close to the HC_HT cluster of the crater rim shocked basalts. The center of this enveloping circle and the average HC_HT component of Lonar crater rim shocked basalts have the same statistical orientation, although the former has steeper dip. This distribution suggests the possibility that the ejected basaltic boulders, which were deposited during the modification stage of Lonar crater evolution, were magnetized in an impact‐induced magnetic field that was rapidly decaying just after the impact. Our present study suggests that the ejected basaltic boulders and Lonar crater rim shocked basalts experienced high shock pressure (≥2 GPa) magnetization during impact.

Exploring the Mineralogy at Lonar Crater with Hyperspectral Remote Sensing

Abstract The earth crust is made up of variety of minerals. These minerals are having very significant applications in our day today life. The various studies, characterizing physical, chemical, electrical, structural properties, have been carried out on the Lonar crater for studying mineralogy, surface morphology and geology but has not been done by remote sensing technology. So, the proposed work focused on exploring the mineralogy at the Lonar crater by using high resolution hyperspectral imageries. The spectral reflectance of minerals was characterized by using FieldSpec4 spectroradiometer. The minerals at Lonar crater were explored by performing preprocessing and spectral analysis. The techniques used in the work are Spectral Angle Mapper and Spectral Feature Fitting. The results of the work marked the presence of pigeonite and augite at Lonar crater which indicates that this crater is the result of extrusive volcanic activity. Also, the presence of augite underneath basaltic igneous rocks as the rock type of Lonar crater. The salinity of the Lonar lake is proved by the presence of mirabilite and salt. Thus, the important results of this work are presence of minerals quartz, actinol, jarosite, pigeonite, augite, albite, mirabilite and scolecite. The significance of these minerals related to the crater is discussed here. It also validated the existence of these minerals which were identified through the previous geological, chemical, physical, electrical and magnetic studies and the minerals pyrite, chlorite, richter, illite, limonite, allanite, amphibolite and margarite were also identified.

Magnetic Anomaly and Model of the Lonar Meteorite Impact Crater in Maharashtra, India

The ground magnetic field of the Lonar impact crater (Maharashtra State, India) and its surrounding area was measured and studied utilizing 2.5-dimensional potential field modelling. Field data showed the crater depression is associated with a strong circular negative anomaly with an amplitude of more than 1000 nT. The negative anomaly, however, decreases smoothly while moving from south to north. Most of the crater rim exhibits anomalous positive values. Negative anomalies at the rim are seen in the south–southwestern sections and coinciding in the northeastern section with the Dhar valley. Our study shows that most of the anomaly is caused by the topographic effect and a strong SE directed natural remanent magnetization of Deccan Trap basalts, which are the target of the Lonar-creating projectile. The magnetic anomaly of the relatively weakly magnetized impact-produced allochthonous breccia and post-impact sediments is small, being less than 150 nT.

Physical Properties of Basalt Ejecta Boulders at Lonar Crater, India: Insights Into the Target Heterogeneity and Impact Spallation Processes in Basalt With Application to Mars

AbstractThe 1.88‐km‐diameter Lonar crater emplaced in the Deccan basalt is an excellent terrestrial analog of bowl‐shaped impact craters on Mars. It contains a pristine ejecta blanket with abundant basalt boulders. We measured the density, porosity, P and S wave velocities and attenuation, magnetic susceptibility, uniaxial compressive strength, and tensile strength of 313 core specimens from 65 basalt ejecta boulders. Using these values, we quantified the gross physical properties of preimpact target and applied them in the cratering equations and estimated the spall plate dimensions and ejection distances. The impact of 35‐m‐radius projectile with 20 km/s velocity on the basaltic target with 77.2‐MPa dynamic tensile strength, 4,163 m/s P wave velocity, and 2.56 g/cm3 density gives a spall thickness range (0.2 to 9.7 m) similar to the observed boulder sizes at Lonar crater. Because aqueous weathering and vesicularity are present in the target, the Lonar impact produced smaller spall sizes than those expected from a massive basalt target. We also measured the ejecta boulder sizes and shapes around a fresh impact crater (of similar size and target to Lonar) in Arcadia Planitia on Mars and calculated the spall thicknesses. The low‐velocity impact (5.5 km/s) of 50‐m‐radius projectile on the target similar to Lonar basalt gives a spall thickness range (1 to 25 m) similar to the observed boulder sizes at the Martian impact crater. The impact craters of similar sizes and targets on Earth and Mars produced different spall boulder size distributions reflecting the distinct impact conditions on these planets.

A High-Temperature Impact Condensate of the Lonar Crater (India)

A high-calcium high-temperature condensate is detected in the Earth’s impact Lonar crater for the first time. Its finding confirms in practice the theoretical conclusions made earlier from the experimental results. The high-silica condensate found in the Lonar crater, which is similar to those ones in the Zhamanshin crater and in the lunar regolith, confirms the absence of a correlation between the compositions of the target and the impact condensates. The presence of high-temperature condensate glasses in ring structures may be one of the diagnostic criteria to differentiate between volcanogenic and impact formations.

Identification of a meteoritic component using chromium isotopic composition of impact rocks from the Lonar impact structure, India

AbstractThe existence of mass‐independent chromium isotope variability of nucleosynthetic origin in meteorites and their components provides a means to investigate potential genetic relationship between meteorites and planetary bodies. Moreover, chromium abundances are depleted in most surficial terrestrial rocks relative to chondrites such that Cr isotopes are a powerful tool to detect the contribution of various types of extra‐terrestrial material in terrestrial impactites. This approach can thus be used to constrain the nature of the bolide resulting in breccia and melt rocks in terrestrial impact structures. Here, we report the Cr isotope composition of impact rocks from the ~0.57 Ma Lonar crater (India), which is the best‐preserved impact structure excavated in basaltic target rocks. Results confirm the presence of a chondritic component in several bulk rock samples of up to 3%. The impactor that created the Lonar crater had a composition that was most likely similar to that of carbonaceous chondrites, possibly a CM‐type chondrite.

Shear velocity structural characterization around the Lonar crater using joint inversion of ambient noise HVSR and Rayleigh wave dispersion

The Lonar crater in India is the only known hyper-velocity impact crater formed in basalt target on the Earth formed by an extra-terrestrial meteorite impact, with a distinct shock-induced metamorphosed signature. To understand the effects of impact deformation, fracturing, emplacement of the shock-metamorphosed ejecta material and sedimentation structure in the target basalt around the crater, we investigate the sub-surface shear velocity structure around the Lonar crater region. We use three components, 24-hour records of ambient noise (or microtremor) H/V spectral ratio (HVSR) and Rayleigh wave dispersion data through cross-correlation of ambient noise, obtained from 20 broadband seismic stations around the Lonar crater. The HVSR pattern across the Lonar crater does not present common frequency peaks, suggesting a laterally varying lithological arrangement around the crater. We observe that the HVSR curves at the stations show one or more peaks, below 1 Hz and above 2 Hz. To obtain the average sub-surface shear velocity models, we use the joint inversion of the phase dispersion curves of fundamental and higher mode Rayleigh wave with HVSR data sets, using neighborhood algorithm, in the frequency range 0.2–20 Hz and explored up to 750 m depth. As a reliability-check for the shear velocity models, we compute the theoretical HVSR by forward modeling. The theoretical and observed HVSR peaks match fairly well at each broadband station spread across the Lonar crater. The results show the existence of the fractured/weathered and sedimentary layers and also of the fundamental and higher modes of Rayleigh waves altering the shape of the HVSR and the Rayleigh wave dispersion curves. A pattern of the multiple layers in the sediment–package is visible in the shallow and deeper parts up to 600 m depths across the Lonar crater, but with spatial variations, which may be due to variations in the extent of the fractured zone. This spatial asymmetry of shear velocity profiles might also be the effect of an obliquity impact at the Lonar crater. The significance of such a joint analysis of different datasets of surface waves and HVSR is intended to reduce non-uniqueness involved in the non-linear inversions and present more acceptable sub-surface models to enhance the near-surface geophysical understanding of the impacted structure around the Lonar Crater.

Evidence for a chondritic impactor, evaporation-condensation effects and melting of the Precambrian basement beneath the ‘target’ Deccan basalts at Lonar crater, India

The ∼1.88km diameter Lonar impact crater formed ∼570ka ago and is an almost circular depression hosted entirely in the Poladpur suite of the ∼65Ma old basalts of the Deccan Traps. To understand the effects of impact cratering on basaltic targets, commonly found on the surfaces of inner Solar System planetary bodies, major and trace element concentrations as well as Nd and Sr isotopic compositions were determined on a suite of selected samples composed of: basalts, a red bole sample, which is a product of basalt alteration, impact breccia, and impact glasses, either in the form of spherules (<1mm in diameter) or non-spherical impact glasses (>1mm and <1cm). These data include the first highly siderophile element (HSE) concentrations for the Lonar spherules. The chemical index of alteration (CIA) values for the basalts and impact breccia (36.4–42.7) are low while the red bole sample shows a high CIA value (55.6 in the acid-leached sample), consistent with its origin by aqueous alteration of the basalts. The Lonar spherules are classified into two main groups based on their CIA values. Most spherules show low CIA values (Group 1: 34.7–40.5) overlapping with the basalts and impact breccia, while seven spherules show significantly higher CIA values (Group 2: >43.0). The Group 1 spherules are further subdivided into Groups 1a and 1b, with Group 1a spherules showing higher Ni and mostly higher Cr compared to the Group 1b spherules. Iridium and Cr concentrations of the spherules are consistent with the admixture of 1–8wt% of a chondritic impactor to the basaltic target rocks. The impactor contribution is most prominent in the Group 1a and Group 2 spherules, which show higher Ni/Co, Ni/Cr and Cr/Co ratios compared to the target basalts. In contrast, the Group 1b spherules show major and trace element compositions that overlap with those of the impact breccia and are characterized by high EFTh (Enrichment Factor for Th defined as the Nb-normalized concentration of Th relative to that of the average basalt) as well as fractionated La/Sm(N), and higher large ion lithophile element (LILE) concentrations compared to the basalts. The relatively more radiogenic Sr and less radiogenic Nd isotopic composition of the impact breccia and non-spherical impact glasses compared to the target basalts are consistent with melting and mixing of the Precambrian basement beneath the Deccan basalt with up to 15wt% contribution of the basement to these samples. Variations in the moderately siderophile element (MSE) concentration ratios of the impact breccia as well as all the spherules are best explained by contributions from three components – a chondritic impactor, the basaltic target rocks at Lonar and the basement underlying the Deccan basalts. The large variations in concentrations of volatile elements like Zn and Cu and correlated variations of EFCu-EFZn, EFPb-EFZn, EFK-EFZn and EFNa-EFZn, particularly in the Group 1a spherules, are best explained by evaporation-condensation effects during impact. While most spherules, irrespective of their general major and trace element composition, show a loss in volatile elements (e.g., Zn and Cu) relative to the target basalts, some spherules, mainly of Group 1, display enrichments in these elements that are interpreted to reflect the unique preservation of volatile-rich vapour condensates resulting from geochemical fractionation in a vertical direction within the vapour cloud.

New insights on petrography and geochemistry of impactites from the Lonar crater, India

AbstractThe Lonar impact crater, India, is one of the few known terrestrial impact craters excavated in continental basaltic target rocks (Deccan Traps, ~65 Ma). The impactites reported from the crater to date mainly include centimeter‐ to decimeter‐sized impact‐melt bombs, and aerodynamically shaped millimeter‐ and submillimeter‐sized impact spherules. They occur in situ within the ejecta around the crater rim and show schlieren structure. In contrast, non–in situ glassy objects, loosely strewn around the crater lake and in the ejecta around the crater rim do not show any schlieren structure. These non–in situ fragments appear to be similar to ancient bricks from the Daityasudan temple in the Lonar village. Synthesis of existing and new major and trace element data on the Lonar impact spherules show that (1) the target Lonar basalts incorporated into the spherules had undergone minimal preimpact alteration. Also, the paleosol layer as preserved between the top‐most target basalt flow and the ejecta blanket, even after the impact, was not a source component for the Lonar impactites, (2) the Archean basement below the Deccan traps were unlikely to have contributed material to the impactite parental melts, and (3) the impactor asteroid components (Cr, Co, Ni) were concentrated only within the submillimeter‐sized spherules. Two component mixing calculations using major oxides and Cr, Co, and Ni suggest that the Lonar impactor was a EH‐type chondrite with the submillimeter‐sized spherules containing ~6 wt% impactor components.

An unusual occurrence of coesite at the Lonar crater, India

AbstractCoesite has been identified within ejected blocks of shocked basalt at Lonar crater, India. This is the first report of coesite from the Lonar crater. Coesite occurs within SiO2 glass as distinct ~30 μm spherical aggregates of “granular coesite” identifiable both with optical petrography and with micro‐Raman spectroscopy. The coesite+glass occurs only within former silica amygdules, which is also the first report of high‐pressure polymorphs forming from a shocked secondary mineral. Detailed petrography and NMR spectroscopy suggest that the coesite crystallized directly from a localized SiO2 melt, as the result of complex interactions between the shock wave and these vesicle fillings.

A new report of Nocardiopsis valliformis strain OT1 from alkaline Lonar crater of India and its use in synthesis of silver nanoparticles with special reference to evaluation of antibacterial activity and cytotoxicity.

The authors report the biological synthesis of silver nanoparticles (AgNPs) by alkaliphilic actinobacterium Nocardiopsis valliformis OT1 strain isolated for the first time from Lonar crater, India. The primary detection of silver NPs formation was made by colour change from colourless to dark brown and confirmed by UV–Vis spectrum of AgNPs at 423 nm, specific for AgNPs. Further, AgNPs were characterized by nanoparticle tracking analysis, Zeta sizer, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) analyses. FTIR analysis showed the presence of proteins as capping agent. TEM analysis revealed the formation of spherical and polydispersed AgNPs within the size range of 5–50 nm. The antimicrobial activity of silver nanoparticles against Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis was evaluated. The AgNPs showed the maximum antibacterial activity against B. subtilis (Gram positive) and the minimum against E. coli (Gram negative). The minimal inhibitory concentration values of AgNPs for the tested bacteria were found to be in the range of 30–80 µg/mL. The AgNPs demonstrated higher antibacterial activity against all the bacteria tested as compared with the commercially available antibiotics. The cytotoxicity of biosynthesized AgNPs against in vitro human cervical cancer cell line (HeLa) demonstrated a dose–response activity. The IC50 value was found to be 100 µg/mL of AgNPs against cancer HeLa cell line.

Target rocks, impact glasses, and melt rocks from the Lonar crater, India: Highly siderophile element systematics and Sr‐Nd‐Os isotopic signatures

AbstractThe Lonar crater is a ~0.57‐Myr‐old impact structure located in the Deccan Traps of the Indian peninsula. It probably represents the best‐preserved impact structure hosted in continental flood basalts, providing unique opportunities to study processes of impact cratering in basaltic targets. Here we present highly siderophile element (HSE) abundances and Sr‐Nd and Os isotope data for target basalts and impactites (impact glasses and impact melt rocks) from the Lonar area. These tools may enable us to better constrain the interplay of a variety of impact‐related processes such as mixing, volatilization, and contamination. Strontium and Nd isotopic compositions of impactites confirm and extend earlier suggestions about the incorporation of ancient basement rocks in Lonar impactites. In the Re‐Os isochron plot, target basalts exhibit considerable scatter around a 65.6 Myr Re‐Os reference isochron, most likely reflecting weathering and/or magma replenishment processes. Most impactites plot at distinctly lower187Re/188Os and187Os/188Os ratios compared to the target rocks and exhibit up to two orders of magnitude higher abundances of Ir, Os, and Ru. Moreover, the impactites show near‐chondritic interelement ratios ofHSE. We interpret our results in terms of an addition of up to 0.03% of a chondritc component to most impact glasses and impact melt rocks. The magnitude of the admixture is significantly lower than the earlier reported 12–20 wt% of extraterrestrial component for Lonar impact spherules, reflecting the typical difference in the distribution of projectile component between impact glass spherules and bulk impactites.

Basaltic glass formed from hydrovolcanism and impact processes: Characterization and clues for detection of mode of origin from VNIR through MWIR reflectance and emission spectroscopy

The CheMin X-ray diffraction instrument on-board the Curiosity rover in Gale crater has measured a consistent X-ray amorphous component in drill core samples examined to-date, clearly demonstrating that X-ray amorphous materials are a significant fraction of the martian surface layer. Glasses are potential components of this amorphous material and in this study, basaltic tephras from several hydro- and glaciovolcanic centers, as well as impact melts from India's Lonar Crater, were examined using thin section petrography, visible and near-infrared reflectance and mid-wave infrared emission spectroscopy as well as measuring major and minor element chemistry of representative samples using X-ray fluorescence (XRF) spectroscopy. The objectives of this study have been to look for distinguishing characteristics between volcanic and impact glasses and to determine features that indicate whether the glasses are fresh or altered using methods available on current and planned Mars rovers. Spectral features in the visible and near-infrared (VNIR) that can be used as indicators of alteration include the development of hydration features at 1.9 and ∼3µm and a feature attributed to ferric oxide development at 0.48µm. In the mid-wave infrared, it was observed that glass-rich tephra field samples did not display a broad, disordered glass feature near 9–10µm (as is observed in pristine basaltic glasses) but rather a doublet with centers near 9.5 and 11µm attributed in earlier work to incipient devitrification into SiO4 chain and sheet structures respectively. A tentative observation was made that the Si–O bending feature, observed in all the sample spectra near 22µm was broader in the hydro- and glaciovolcanic glass samples than in the impact glass samples. Hydro- and glaciovolcanic glass-rich tephra samples were used as library spectra in linear deconvolution analyses of Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) surface spectral types. These incipiently devitrified glass spectra were selected for all of the surface types and formed close to 40% of the N. Acidalia Planitia spectral type.

A perspective of alkaline Lonar Lake, Maharashtra, India with reference to its hydrochemistry

The inland Lonar Lake, encompassing a circular area of about 1 sq. km is situated in Buldhana district, Maharashtra state, India. The lake is part of the Lonar crater believed to have formed due to meteoric impact. It is third largest natural salt-water lake in the world. The lake water is not only saline, but also highly alkaline. In recent years, it is believed that the alkalinity and salinity of the lake water is being diluted with increased lake water level due to external inputs like seepage of water into the lake from nearby surface reservoirs. Studies on hydrochemical and isotopic signatures of lake water, and also lake water levels were carried out for one year to understand the lake dynamics. The generated data were compared with those available in the literature. This comparison showed that the water level and hydrochemistry of lake water are controlled by the local rainfall and evaporation, and that there are no other external water inputs to the lake.