Thermal evolution of trans‐Neptunian objects,icy satellites,and minor icy planets in the early solar system

Numerical simulations are performed to understand the early thermal evolution and planetary scale differentiation of icy bodies with the radii in the range of 100–2500 km. These icy bodies include trans‐Neptunian objects, minor icy planets (e.g., Ceres, Pluto); the icy satellites of Jupiter, Saturn, Uranus, and Neptune; and probably the icy‐rocky cores of these planets. The decay energy of the radionuclides, ²⁶Al, ⁶⁰Fe, ⁴⁰K, ²³⁵U, ²³⁸U, and ²³²Th, along with the impact‐induced heating during the accretion of icy bodies were taken into account to thermally evolve these planetary bodies. The simulations were performed for a wide range of initial ice and rock (dust) mass fractions of the icy bodies. Three distinct accretion scenarios were used. The sinking of the rock mass fraction in primitive water oceans produced by the substantial melting of ice could lead to planetary scale differentiation with the formation of a rocky core that is surrounded by a water ocean and an icy crust within the initial tens of millions of years of the solar system in case the planetary bodies accreted prior to the substantial decay of ²⁶Al. However, over the course of billions of years, the heat produced due to ⁴⁰K, ²³⁵U, ²³⁸U, and ²³²Th could have raised the temperature of the interiors of the icy bodies to the melting point of iron and silicates, thereby leading to the formation of an iron core. Our simulations indicate the presence of an iron core even at the center of icy bodies with radii ≥500 km for different ice mass fractions.     

Effect of hot injections on electromagnetic ion-cyclotron waves in inner magnetosphere of Saturn

Encounter of Voyager with Saturn’s environment revealed the presence of electromagnetic ion-cyclotron waves (EMIC) in Saturnian magnetosphere. Cassini provided the evidence of dynamic particle injections in inner magnetosphere of Saturn. Also inner magnetosphere of Saturn has highest rotational flow shear as compared to any other planet in our solar system. Hence during these injections, electrons and ions are transported to regions of stronger magnetic field, thus gaining energy. The dynamics of the inner magnetosphere of Saturn are governed by wave-particle interaction. In present paper we have investigated those EMIC waves pertaining in background plasma which propagates obliquely with respect to the magnetic field of Saturn. Applying kinetic approach, the expression for dispersion relation and growth rate has been derived. Magnetic field model has been used to incorporate magnetic field strength at different latitudes for radial distance of \(6.18~R_{{s}}\) (\(1~R_{{s}}= 60{,}268~\mbox{km}\)). Various parameters affecting the growth of EMIC waves in cold bi-Maxwellian background and after the hot injections has been studied. Parametric analysis inferred that after hot injections, growth rate of EMIC waves increases till \(10^{\circ}\) and decreases eventually with increase in latitude due to ion density distribution in near-equatorial region. Also, growth rate of EMIC waves increases with increasing value of temperature anisotropy and AC frequency, but the growth rate decreases as the angle of propagation with respect to \(B_{0}\) (Magnetic field at equator) increases. The injection events which assume the Loss-cone distribution of particles, affect the lower wave numbers of the spectra.     

Origin of red color of the Lower Siwalik palaeosols: A micromorphological approach

Palaeosols associated with fluvial of the Siwalik Group are and lacustrine deposits that occur as thick multiple pedocomplexes. The bright red color of the palaeosol beds has been earlier interpreted as a result of hot and arid palaeoclimate. However, as against this view, our investigations of the bright red palaeosol beds of the Lower Siwaliks suggest that the climate was cool and subhumid, instead of hot and arid during the deposition of these beds. Since cold climate is not very conducive to impart red coloration, further research is needed to explain the cause of these red beds. For this, the micromorphological study of soil thin sections was done which showed the presence of features such as dissolution and recrystallisation of quartz, feldspar and mica, compaction, slickensides, presence of calcite spars, subrounded and cracked nature of quartz grains, microfabric, complex patterns of birefringence fabrics, pigmentary ferric oxides, thick cutans and cementation by calcite. These features indicate that diagenesis took place on a large scale in these sediments. The positive Eh and neutral-alkaline pH of soils also suggest that the conditions were favorable for the formation of diagenetic red beds. During burial diagenesis of sediments, the hydroxides of ferromagnesian minerals got converted into ferric oxide minerals （hematite）. During deep burial diagenesis smectite was converted into illite and the preponderance of illite over smectite with increasing depth of burial also indicates the diagenesis of sediments. Thus, the red color of the Lower Siwalik palaeosols seems to be due mainly to the burial diagenesis of sediments and does not appear to be due to the then prevailing climatic condition.     

Robe’s problem: its extension to 2+2 bodies

In the problem of 2+2 bodies in the Robe’s setup, one of the primaries of mass m^*₁m^{*}_{1} is a rigid spherical shell filled with a homogeneous incompressible fluid of density ρ ₁. The second primary is a mass point m ₂ outside the shell. The third and the fourth bodies (of mass m ₃ and m ₄ respectively) are small solid spheres of density ρ ₃ and ρ ₄ respectively inside the shell, with the assumption that the mass and the radius of third and fourth body are infinitesimal. We assume m ₂ is describing a circle around m^*₁m^{*}_{1}. The masses m ₃ and m ₄ mutually attract each other, do not influence the motion of m^*₁m^{*}_{1} and m ₂ but are influenced by them. We also assume masses m ₃ and m ₄ are moving in the plane of motion of mass m ₂. In the paper, the equations of motion, equilibrium solutions, linear stability of m ₃ and m ₄ are analyzed. There are four collinear equilibrium solutions for the given system. The collinear equilibrium solutions are unstable for all values of the mass parameters μ,μ ₃,μ ₄. There exist an infinite number of non collinear equilibrium solutions each for m ₃ and m ₄, lying on circles of radii λ,λ′ respectively (if the densities of m ₃ and m ₄ are different) and the centre at the second primary. These solutions are also unstable for all values of the parameters μ,μ ₃,μ ₄, φ, φ′. Such a model may be useful to study the motion of submarines due to the attraction of earth and moon.     

Transition metals (Mn,Ni, Co) doping in TiO<Subscript>2</Subscript> nanoparticles and their effect on degradation of diethyl phthalate

Transition metal-doped TiO₂ nanoparticles are synthesized by sol–gel method. The as-prepared samples are characterized by various techniques to correlate structural and optical properties with chemical nature of dopants and their effect on photocatalytic degradation of diethyl phthalate esters. X-ray diffraction (XRD) reveals that all the samples are crystalline and exhibit anatase as a major phase. Chemical nature of dopants could not affect the formation of anatase and its volume fraction. The crystallite size of undoped and doped TiO₂ nanoparticles varies between 10 and 12 nm as confirmed by XRD and transmission electron microscope. The lowest optical band gap observed is 2.47 eV in Mn-doped TiO₂. Among all the samples, Ni-doped TiO₂ sample shows better photocatalytic activity and degradation of diethyl phthalate due to its lower crystallite size and higher surface area than those of Mn- and Co-doped TiO₂ samples.     

Quaternary alluvial fan sedimentation in the Dehradun Valley Piggyback Basin, NW Himalaya: tectonic and palaeoclimatic implications

ABSTRACT The Dehradun Valley, a synclinal intermontane valley piggyback basin within the Siwalik Group rocks in the NW Himalaya, is separated from the Lesser Himalayan formations in the north by a major intraplate thrust, the Main Boundary Thrust (MBT) and from the Indogangetic Plains in the south by the Himalayan Frontal Fault (HFF). Major parts of the Dehradun Valley are covered by three fans, from west to east the Donga, Dehradun and Bhogpur fans, deposited by streams following the topography produced by activity of the MBT and probable footwall imbricate thrusts, starting at about 50 ka. The Donga and Dehradun fans were fed by small streams and characterized mainly by sediment gravity‐flow deposits (debris flow and mudflow deposits) in the proximal zone, and mostly mudflow deposits and minor braided stream deposits in the middle zone during the period 50–10 ka. Palaeosols were weakly developed in the proximal zone and moderately to strongly developed in the middle zone. The degree of development of palaeosol was mainly a function of rate of sedimentation and to some extent entrenchment of streams into the fan surface. Since 10 ka, deposition has been typically by braided streams. The Bhogpur fan has been marked by deposition from relatively larger braided streams since 50 ka. The fan sequences in the Dehradun Valley are synorogenic and their deposition started due to activity of the southern footwall imbricate of the MBT, i.e. Bhauwala Thrust on the Donga and Dehradun fans. In these fans, major fan sequences show retrogradation (50–10 ka) related to a decrease in the activity of the MBT and related imbricates and activity of more hinterlandward imbricates with time. After 10 ka a thin prograding sequence was deposited due to uplift of the fans, which resulted from the activity on a thrust in the distal parts of the fans. It suggests an out‐of‐sequence activity of faults in the MBT imbricate system. Cross‐faults divide the Siwalik formations in the footwall of the MBT into three blocks, which were marked by decreasing subsidence or possibly uplift from east to west. Thrusting on the HFF was not piggyback type but synchronous with activity of the MBT and its imbricates. The development of the Mohand fault‐bend anticline above the HFF changed the nature of the basin from foreland to piggyback type, shed minor colluvial deposits prior to 10 ka, and folded the southernmost fan deposits in the western, narrow parts of the valley. A major change in climate from a cold, dry climate with strong seasonal variations prevailing since 50 ka to warm and humid climate at about 10 ka resulted in a change in depositional processes from sediment gravity‐flows to braided streams.     

Clay Minerals in Soils as Evidence of Holocene Climatic Change, Central Indo-Gangetic Plains, North-Central India

Clay mineral assemblages of a soil chrono-association comprising five fluvial surface members (QGH1 to QGH5) of the Indo-Gangetic Plains between the Ramganga and Rapti rivers, north-central India, demonstrate that pedogenic interstratified smectite–kaolin (Sm/K) can be considered as a potential indicator for paleoclimatic changes during the Holocene from arid to humid climates. On the basis of available radiocarbon dates, thermoluminescence dates, and historical evidence, tentative ages assigned to QGH1 to QGH5 are <500 yr B.P., >500 yr B.P., >2500 yr B.P., 8000 TL yr B.P., and 13,500 TL yr B.P., respectively. During pedogenesis two major regional climatic cycles are recorded: relatively arid climates between 10,000–6500 yr B.P. and 3800–? yr B.P. were punctuated by a warm and humid climate. Biotite weathered to trioctahedral vermiculite and smectite in the soils during arid conditions, and smectite was unstable and transformed to Sm/K during the warm and humid climatic phase (7400–4150 cal yr B.P.). When the humid climate terminated, vermiculite, smectite, and Sm/K were preserved to the present day. The study suggests that during the development of soils in the Holocene in alluvium of the Indo-Gangetic Plains, climatic fluctuations appear to be more important than realized hitherto. The soils older than 2500 yr B.P. are relict paleosols, but they are polygenetic because of their subsequent alterations.     

Release of Chromium from Soils with Persulfate Chemical Oxidation

An important part of the evaluation of the effectiveness of persulfate in situ chemical oxidation (ISCO) for treating organic contaminants is to identify and understand its potential impact on metal co‐contaminants in the subsurface. Chromium is a redox‐sensitive and toxic metal the release of which poses considerable risk to human health. The objective of this study was to investigate the impact of persulfate chemical oxidation on the release of chromium from three soils varying in physical‐chemical properties. Soils were treated with unactivated and activated persulfate [activated with Fe(II), Fe(II)‐EDTA, and alkaline pH] at two different concentrations (i.e., 41 mM and 2.1 mM persulfate) for 48 h and 6 months and were analyzed for release of chromium. Results show that release of chromium with persulfate chemical oxidation depends on the soil type and the activation method. Sandy soil with low oxidant demand released more chromium compared to soils with high oxidant demand. More chromium was released with alkaline pH activation. Alkaline pH and high Eh conditions favor oxidation of Cr(III) to Cr(VI), which is the main mechanism of release of chromium with persulfate chemical oxidation. Unactivated and Fe(II)‐activated persulfate decreased pH and at low pH in absence of EDTA chromium release is not a concern. These results indicate that chromium release can be anticipated based on the given site and treatment conditions, and ISCO system can be designed to minimize potential chromium release when treating soils and groundwater contaminated with both organic and metal contaminants.     

Metasomatism of ferroan granites in the northern Aravalli orogen,NW India: geochemical and isotopic constraints,and its metallogenic significance

The late Palaeoproterozoic (1.72–1.70 Ga) ferroan granites of the Khetri complex, northern Aravalli orogen, NW India, were extensively metasomatised ~900 Ma after their emplacement, at around 850–830 Ma by low-temperature (ca. 400 °C) meteoric fluids that attained metamorphic character after exchanging oxygen with the surrounding metamorphic rocks. Albitisation is the dominant metasomatic process that was accompanied by Mg and Ca metasomatism. A two-stage metasomatic model is applicable to all the altered ferroan intrusives. The stage I is represented by a metasomatic reaction interface that developed as a result of transformation of the original microcline–oligoclase (An_12–14) granite to microcline–albite (An_1–3) granite, and this stage is rarely preserved. In contrast, the stage II metasomatic reaction front, where the microcline-bearing albite granite has been transformed to microcline-free albite granite, is readily recognisable in the field and present in most of the intrusives. Some of them lack an obvious reaction interface due to the presence of stage II albite granites only. When studied in isolation, these intrusives were incorrectly classified and their tectonic setting was misinterpreted. Furthermore, our results show that the mafic mineralogy of metasomatised granites has a significant impact on the characterisation of such rocks in the magmatic classification and discrimination diagrams. Nevertheless, the stage I metasomatised granites can be appropriately characterised in these diagrams, whereas the characterisation of the stage II granites will lead to erroneous interpretations. The close spatial association of these high heat producing ferroan granites with iron oxide–copper–gold (IOCG), U and REE mineralisation in the region indicates a genetic link between the metasomatism and the mineralisation. World-class IOCG, U and REE deposits are associated with metasomatised ferroan granites, suggesting that such a relationship may act as a critical first-order exploration target for undiscovered mineral deposits.