Mineralogical Characterization of Mare Australe: A Unique Region on the Moon
Abstract
Mare Australe (47.77°S, 91.99°E) is a volcanic province ~1000 km in diameter at the eastern nearside and farside boundary of the Moon. It consists of 248 mapped basaltic patches arranged in a more-or-less circular pattern. Initially classified as a “distinct” basin, it was later considered a “no topographic basin” due to a lack of identifiable topographic features. The results from the GRAIL mission, did not confirm the presence of a basin coinciding with the previously proposed one. Instead, GRAIL suggested the presence of a ~880 km diameter impact structure northwards named the Australe North Basin centered at 35.5°S, 96°E. In the earlier study geological evidences were provided to further establish the presence of the Australe North Basin. Volcanic activity at Lacus Solitudinis and Bowditch Crater, once thought to be isolated, is now linked to Australe North Basin. Based on the re-defined basin boundaries in the region a significant part of Mare Australe’s basalts lie outside the boundaries of Australe North. These basaltic units of Mare Australe remain largely uncharacterized. In this seminar, I will present a detailed investigation into the mineralogical diversity of the Mare Australe region. This study aims to shed light on the nature and origin of the distinctive style of volcanism in the region, highlighting the unique geological setting of Mare Australe and its implications for lunar volcanic evolution.
Atmosphere Characterization of the Hot-Jupiter Exoplanets
Abstract
Hot Jupiters, tidally locked to their host stars, exhibit extreme day–night temperature contrasts that drive vigorous atmospheric circulation. In my recent work, I analytically and numerically quantified how this heat redistribution shapes their temperature–pressure (T–P) profiles and dayside emission spectra. Using discrete space theory radiative transfer simulations, I demonstrated that reduced heat redistribution leads to hotter daysides, stronger thermal inversions, and higher emission fluxes. Application to exoplanet XO-1b revealed near-complete heat redistribution, resolving key degeneracies in its atmospheric characterization. Beyond circulation, my research also addresses two crucial aspects:
• Radius Inflation: Ionized atmospheric flows coupled with magnetic fields generate Ohmic dissipation within the radiative and convective zones. MESA evolutionary simulations, parameterized by atmospheric flow velocities, successfully reproduce the observed inflated radii of hot Jupiters through this internal heating mechanism.
• Spectral Separation: I have generalized Chandrasekhar’s diffuse reflection theory to unify thermal emission and scattering, allowing precise separation of planetary spectra from stellar contamination in ultra-hot Jupiters.
In future work, I plan to integrate equilibrium and non-equilibrium chemistry into circulation models to better capture day–night variations in chemical abundances to study the effect of atmospheric heat redistribution on the atmospheric chemistry and finally its imprints on the emission spectra. Additionally, I aim to extend these frameworks to lower-mass, potentially habitable tidally locked terrestrial planets to inform climate and habitability studies. I also plan to develop improved radiative transfer tools that can simultaneously handle complex emission, scattering, and chemical processes, providing stronger predictive power for upcoming JWST and ARIEL observations.
Towards understanding lunar hydration using Chandrayaan-1 and Chandrayaan-2 NIR spectrometers
Abstract
The Moon Mineralogy Mapper (M3) onboard Chandrayaan-1 has been extensively utilized to map the global surface
composition and detect OH/H2O on the lunar surface. It was the first instrument to systematically detect and map the
3-µm absorption feature associated with hydration, using observations acquired at different times of the lunar day.
However, the compositional dependencies and temporal variability of this feature, especially in the polar regions,
remain poorly understood. Moreover, M3’s limited spectral coverage—extending only up to 3.0 µm—restricted its
ability to fully characterize the hydration feature and to distinguish between OH and H2O. The Imaging InfraRed
Spectrometer (IIRS) onboard Chandrayaan-2 addresses this limitation by extending the spectral range to 5.0 µm,
thus enabling discrimination between OH and H2O signatures. However, IIRS data also come with certain limitations
that must be carefully understood before it can be reliably applied at the global scale. In this talk, I will present our i
ndependent methodology for processing IIRS data in parallel with M3, aimed at achieving cross-calibration and a
robust comparison of hydration features. We have selected multiple overlapping IIRS observations, including
well-characterized landing sites, and categorized them based on lunar local time to study diurnal variations.
After applying dark current subtraction, radiometric correction, and thermal emission modeling, the IIRS spectra
were geometrically aligned with M3 and corrected for topographic and photometric effects. I will share our
preliminary results, insights gained from the IIRS data processing workflow, and our outlook for integrating IIRS
and M3 data in a comprehensive global-scale analysis.
Cosmogenic Nuclides in Meteorites: Constraining Cosmic Ray Exposure and Terrestrial Ages
Abstract
Cosmogenic nuclides, produced by interactions between cosmic rays and meteoritic matter, are powerful tools for determining the cosmic ray exposure (CRE) ages and terrestrial residence times of meteorites. This talk will highlight the combined approach using Accelerator Mass Spectrometry (AMS) along with Noble Gas Mass Spectrometry (NGMS) to estimate both CRE and terrestrial ages. The talk will discuss how radionuclides such as ¹⁰Be, together with stable noble gases like ²¹Ne, help reconstruct the exposure history, shielding conditions, and delivery mechanisms of meteorites. These methods play a key role in understanding the journey of meteoroids from space to Earth and contribute toward developing robust AMS measurement protocols at PRL.
Concentrations of Hydrogenated, nitrogenated, & protonated sulfuric acid ions due to GCR (Galactic Cosmic Rays) impact ionization in lower atmosphere of Venus.
Abstract
Solar radiation interacting with the Venusian atmosphere produces two prominent ionization layers: V2 (~140 km) and V1 (~125 km). However, due to the high atmospheric density, only Galactic Cosmic Rays (GCRs) can penetrate into the deeper layers of the Venusian atmosphere. As cosmic ray air showers propagate through the Venusian atmosphere, they develop extensively until reaching a maximum, typically located between 60 and 70 km, below this altitude, the flux of secondary particles steadily declines due to their insufficient energy to sustain ionization. Previous studies have theorized the ion-pair production rates in this region with negligible focus on ionic species responsible.
This presentation will begin with a general overview of the Venusian atmosphere, followed by a concise explanation of the methodology and chemical model we have used to compute electron densities and ion concentrations for 74 ion species in this region. The talk will conclude with a discussion on of some of the dominant ions identified in the lower region, for example hydrated hydronium ions and hydrated ions of NO2-, CO3-.
Farside Volcanism on the Moon: A Remote Sensing Perspective
Abstract
Volcanism on the Moon is primarily manifested in the form of mare basalts, which cover ⁓17% of its surface. Mare basalts exhibit significant compositional diversity and are mainly concentrated within and adjacent to the large circular impact structures, and have a total volume estimated at ~107 km3. Interestingly, the distribution of mare basalts is highly asymmetric, whereby the nearside hosts extensive basaltic emplacements and the farside exhibits remarkably fewer mare basalts. In my talk, I will be providing a detailed account of how the understanding of this fundamental dichotomy has evolved from the first glimpse of the farside by Luna 3 in 1959 to present-day (with missions like Clementine, Lunar Prospector, LRO, Chandrayaan, Kaguya, GRAIL, Chang’e). Despite these advances, key questions remain unanswered on the nearside-farside dichotomy in volcanism. I will discuss the existing gaps in the knowledge and the objectives of my thesis. The talk will conclude with preliminary results based on morphological and chronological studies of the Freundlich-Sharonov Basin, one of my study areas on the farside of the Moon that exhibits evidence of mare emplacement.
Development of Readout Electronics for Plastic Scintillators Coupled with a Photomultiplier Tubes (PMTs) for a Hard X-ray Compton Polarimeter
Abstract
Photons preferentially undergo Compton scatter perpendicular to the plane of polarization, a property that enables the measurement of linear polarization in hard X-rays. A Compton polarimeter employs a low-Z scatterer to maximize the probability of Compton scattering. This central scatterer is surrounded by a high-Z absorber, which detects the azimuthal distribution of scattered photons. In such a configuration, the lowest photon energy at which polarization can be effectively measured is determined by the lower energy detection efficiency of the scatterer. The efficiency is, in turn, limited by the noise performance of the readout electronics.
In this seminar, I will present an overview of the design considerations of the Hard X-ray Compton Polarimeter, with a focus on the development of readout electronics for the scatterer, a plastic scintillator coupled with a PMT. I will also discuss the experiment setup to characterize its detection efficiency at lower energies, aiming to improve the polarimeter sensitivity.
Investigation of Organic Matter in Differentiated Meteorites: Unveiling Indigenous Origins and Impact Dynamics
Abstract
The nature of organic matter in meteorites provides insights into early solar system chemistry and the evolutionary histories of their parent bodies, reflecting processes from nucleosynthesis and dust formation to planetesimal and planetary development over the last 4.5 billion years. This talk provides an overview of the first detailed investigation into the nature and origin of insoluble organic matter (IOM) in aubrites, a rare class of differentiated meteorites. I will present a multitechnique analysis of IOM in aubrites and enstatite chondrites, aimed at understanding the extent of organic distribution within the protoplanetary disk and the physicochemical processes that offer essential clues to their parent body evolution.
In this seminar, I will discuss the spectroscopic analyses of the IOM in aubrites compared with chondrite IOM to understand the structural and molecular heterogeneity in different meteorite classes. Further I will be discussing the microscopic studies of these organics highlighting the different carbon morphologies present in aubrites. The results offer new insights into the complex evolutionary history of aubrite parent bodies and contribute to a broader understanding of organic matter preservation in differentiated planetary materials.
N-Body Integration Model for Dust Dynamics and Flux Estimation in Inner Solar System
Abstract
Interplanetary Dust Particles (IDPs), originating from the Asteroid Belt, Kuiper Belt, Oort Cloud, and comets, are fundamental to many Solar System phenomena such as Zodiacal Light and meteor showers. As these particles spiral inward toward the Sun, their orbits are altered by a complex interplay of gravitational and non-gravitational forces, leading to gradual perturbations in their orbital elements. The mathematical formulation of the force models, orbital perturbation equations, and their impact on dust evolution will be discussed. We utilize and analyse the N-body problem using Everhart’s RA15 version of the RADAU integrator, which is particularly well-suited for handling stiff orbital equations. I will be presenting results highlighting how Mean Motion Resonances (MMRs) facilitate the capture and long-term trapping of dust particles near planets which can alter dust trajectories. Additionally, methodologies for statistical estimation of dust flux on planetary surfaces by analysing the position of dust particles over time during their close encounters with planets will be discussed. The velocity distribution of impacting particles will also be examined to provide a more complete picture of dust-planet interactions.
Understanding evolution of cometary volatiles
Abstract
Understanding the evolution of volatiles on the surfaces and subsurfaces of comets is crucial to studying their thermal, chemical, and structural history. This talk will provide an overview of the key physical processes driving volatile sublimation on comets, including heat conduction, sublimation, and gas diffusion through porous subsurface material. I will then discuss previous models of cometary nuclei and comae, highlighting their limitations—such as neglecting long-term thermal evolution, relying on simplified geometries (spherical or quasi-3D), underutilizing recent spacecraft data, and lacking integration between nucleus and coma evolution. Addressing these gaps, my research focuses on developing a model that comprehensively links the cometary surface and subsurface with the cometary atmosphere to study volatile evolution. This includes implementing coupled thermophysical and sublimation modelling across realistic comet geometries to interpret cometary activity better and simulate volatile loss over time—particularly at larger heliocentric distances (>3 AU), where CO and CO₂ dominate over H₂O as primary drivers of activity.
Decoding Aqueous Alteration on Mars: Insights from Water/Rock (WR) ratios in Open and Closed Systems
Abstract
In this talk, I will discuss how water/rock (WR) ratios under open and closed system conditions shape secondary mineral formation on Mars. For this, I shall be analyzing the secondary minerals on both Martian meteorites and terrestrial analogues (Deccan basalts from the Kutch area), which will help in understanding the geochemical conditions responsible for such alteration processes that will offer fresh insights into past climates and alteration histories on Mars.
Investigating the Impact of Hydrogen on Lunar Neutron Leakage Flux
Abstract
The Moon's lack of a magnetic field and atmosphere exposes its surface to ionizing radiation, including the solar wind, solar energetic particles (SEPs), and galactic cosmic rays (GCRs). High-energy GCRs interact with the lunar surface, generating fast neutrons through nuclear reactions. These fast neutrons are moderated by collisions with the nuclei in the lunar soil and can leak out, acting as messengers of the soil’s composition. Studying the neutron leakage spectrum can reveal important information about the abundance of near-surface hydrogen.
In this seminar, I will discuss the production and moderation processes of neutrons within the lunar surface, followed by an explanation of how the leakage neutron flux depends on hydrogen and other elements.
Global Detection of Lunar Pyroclastic Deposits (LPDs)
Abstract
Lunar Pyroclastic Deposits (LPDs) are fine-grained, low-albedo, Fe-Ti-rich volcanic glass-dominated lithological units typically
associated with thin crust and extensional tectonic regimes on the Moon. These deposits are providing key insight into thermal
evolution and volatile inventory of the Moon. However, their remote detection remains challenging due to the spectral similarities
between volcanic glasses and Fe-bearing common lunar minerals (e.g., Olivine, Pyroxene, etc.) in the visible to near-infrared
(VIS-NIR) spectral range.
In this seminar, I will present a novel approach developed for remote detection of LPDs by incorporating morphological
understanding with the spectral analysis covering both the spectral parameters. I will present new global LPDs maps,
based on the Moon Mineralogy Mapper (M3) data of two different optical periods. The results will be validated by
comparing the global outcomes to already reported LPDs. The main outcome of this work is new detections. I will
present a few case studies on new detections and validation to confirm their pyroclastic origin. I will also discuss
the inferences and implications during this seminar.
The Role of Layered Minerals in the Origin of Life Insights from Planetary Analogue Terrestrial Geomaterials
Abstract
How did life begin? Researchers believe that certain minerals, especially clays, played a big role in this process. These minerals can hold onto organic molecules, help chemical reactions happen, and create safe spaces for early life to form. Since they exist on Earth and other planets, they also help us search for signs of life beyond our planet. These layered minerals, abundant in terrestrial and extraterrestrial environments, serve as key indicators of fluid-rock interactions and potential biosignature preservation.
This talk will explore how clays can serve as one of the potential planetary analogue terrestrial geomaterials that can enhance our understanding of life’s emergence. By employing comprehensive biogeochemical fingerprinting, this research will characterize clay minerals in terrestrial settings, assessing their capacity to preserve biosignatures. By studying layered minerals on Earth and extending these findings to available extraterrestrial samples, we can unveil the largely unexplored role of clay minerals in the origin of life, which is essential for planning future astrobiological missions.
A Monte Carlo Approach to Temperature and Spectral Energy Distribution in Protoplanetary Disks
Abstract
A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young star. Understanding the structure and composition of these disks is essential for understanding the processes involved in planet formation. Over the years, various models have been developed to describe the chemical and hydrodynamic processes occurring within these disks. Here, we introduce a Monte Carlo Radiative Transfer (MCRT) model to characterize the temperature distribution and spectral energy throughout the disk and its surrounding envelope. MCRT method provides an efficient means of achieving radiative equilibrium without iteration in systems with temperature-independent opacity sources.
Additionally, the computational time required for this method is comparable to that of pure scattering models. The MCRT approach tracks individual photon packets, allowing for precise identification of energy absorption sites and subsequent adjustments to local cell temperatures. To enforce radiative equilibrium, each absorbed packet is instantly re-emitted, with its frequency selected to correct the cell’s thermal spectrum. These re-emitted packets can undergo scattering, absorption, and re-emission processes until they escape, enabling the system’s temperature and spectral energy distribution (SED) to reach equilibrium. We present the initial results of the simulations for both spherical symmetry models and 2D axisymmetric density structures, comparing the findings with standard benchmark tests.
Identification of Whistler Waves Near Flux Ropes in the Nightside Magnetosphere of Venus
Abstract
Whistler waves are electromagnetic plasma waves which are generated by temperature anisotropy instability in magnetized plasma. These right-handed circularly polarized waves propagate along the ambient magnetic field in a magnetized plasma. Atmospheric lightning has been considered a natural source of whistler waves at Venus. Recent observations from the Parker Solar Probe (PSP) during its fourth Venus Gravity Assist (VGA) detected whistler wave bursts in the Venusian magnetotail, with further analysis indicating a non-planetary origin. Magnetic reconnection, a fundamental plasma process which may be responsible for atmospheric erosion and dynamic magnetic activity in Venus' induced magnetosphere, emerges as a potential candidate. Observations at Earth have detected whistler waves near magnetic reconnection regions. Venus Express observed magnetic flux rope structures, which are formed by reconnection in Venus' magnetotail. This study explores the detection of whistler waves in the vicinity of these flux rope structures, bridging the concept of whistler wave generation via magnetic reconnection at Venus.
Electrostatic Dust Detachment
Abstract
The electrostatic processes are fundamentally important in understanding particle dynamics and the complex dusty plasma environment over the Moon. While many studies have examined dust levitation, the detachment of dust from the lunar surface remains a key factor in understanding the lunar dusty plasma environment. Dust particles on the charged lunar surface experience gravity, cohesion, and electrostatic forces. Typically, the electrostatic force derived from a uniformly charged surface (from Gauss Law) is insufficient to lift the particles against gravity. In this presentation, I will demonstrate that sufficient electric field and coulomb repulsion can be created between the dust and surface due to charge fluctuations on a microscopic scale, which can detach the dust particle from the lunar surface, overcoming dust-surface adhesive force.
Unravelling Mar’s Magmatic Past: Insights from Martian Shergottites
Abstract
Shergottites, constituting around 90% of the Martian meteorite collection, are categorized into various types: basaltic, olivine-phyric, poikilitic, and gabbroic. Notably, poikilitic shergottites are distinct from the other shergottites as they are cumulate and form at the deep interior into the Mars in comparison to the other extrusive members. This study delves into the mineralogy and petrology of a poikilitic shergottite, NWA 1950 to constrain Martian igneous processes and identify mantle source reservoirs for shergottites. Additionally, the olivine-hosted melt inclusions help to constrain parental melt compositions, mantle sources, and formation processes, while also reconstructing magma evolution from emplacement to ascent.
Identification and Characterization of Topside V3 Layer of Venusian Ionosphere
Abstract
The dayside Venusian ionosphere is produced by photoionization (primary) and photoelectron impact (secondary) ionization from solar EUV (10-105 nm) and SXR (0.1-10 nm) radiations producing V2 (~140 km) and V1 (~125 km) layers. Previous observations from missions such as the Mariner, Venera, and Pioneer Venus Orbiter also reported a "bulge" at 160–200 km altitudes. This bulge has not been documented in any of the standard ionospheric model. Moreover, there have been a limited data of the ionospheric observation during low solar activity which further constrain the characterization of this V3 layer. Using electron density profiles observed by VeRa radio occultation experiment under varying solar activity levels and solar zenith angles (SZAs), we examined the bulge, known as the "V3 layer". Our study analyzed over 200 electron density profiles to characterize this V3 layer. In this seminar I will briefly summarize the results of V3 layer morphology and occurrence rate under varying Solar activity and SZA conditions.
Tides as a tool for deciphering internal structures of telluric planets
Abstract
Modelling the tidal deformations observed on the telluric planets is a complementary approach to any seismological data to decipher their internal structure. It provides constraints on internal heterogeneities, as well as rheological and density constraints on materials, enabling tidal 'tomography'. These constraints, coupled with thermodynamic models, allow us to establish the current structure of these objects and help us to understand their geodynamic evolution. In this seminar, we will look at the internal structures of Moon and Mars cores, the process of mantle overturn during the crystallisation of the lunar magma ocean, the persistence of a potentially molten zone in the Martian mantle and the persistence of a significant viscosity contrast between the upper mantle of Venus and the lower mantle. We will also look at the viscosity contrasts between the Martian lithosphere and asthenosphere. The challenges of characterising the existence of heterogeinities in the Moon mantle will be also addressed.
Design and development of PRATHIMA electronics subsystem for LuPEX/Chandrayaan-5 Rover
Abstract
Permittivity and Thermophysical Instrument for Moon’s Aquatic Scout (PRATHIMA) is an instrument onboard ISRO-JAXA LuPEX Rover. PRATHIMA experiment consists of three main sub-systems: (a) a permittivity probe that will be deployed into ~50 cm of the lunar surface (in a pre-drilled borehole), (b) electronics and (3) a deployment mechanism. The Probe consists of pairs of electrodes, which consist of a pair of transmitters and receivers. The complex permittivity of the Lunar Regolith over the low-frequency range (e.g. 1Hz-10 kHz) by measuring the mutual impedance between the transmitter and receiver electrodes. The subsurface complex permittivity (i.e., dielectric constant and conductivity) is derived from the measured phase and amplitude of the mutual impedance. The dielectric constant of water ice embedded in Lunar regolith strongly depends on the frequency in the 10 Hz-10 KHz range and temperature. The design aspects and its development status will be presented in the seminar.
Transmitter electronics of Permittivity and Thermophysical Instrument for Moon’s Aquatic Scout (PRATHIMA)
Abstract
PRATHIMA is one of the selected payloads for the LUPEX/Chandrayaan-5 mission. Its primary objective is to detect and quantify regolith-bound water-ice on the lunar surface/subsurface in the vicinity of the landing site, along the traverse of the rover. The working principle of PRATHIMA involves measuring the dielectric permittivity of water-ice at low frequencies, as water-ice exhibits a significantly high dielectric permittivity in this range. Therefore, a low-frequency sinusoidal signal can be used to excite a medium to study the presence of water-ice content mixed with the regolith.A transmitter electronics system has been designed to generate a programmable low-frequency sinusoidal signal using an FPGA-based Direct Digital Synthesis (DDS) algorithm.
Characterization of Multichannel SDD X-Ray Spectrometer with ASIC Readout
Abstract
In the seminar, I will present the development of a multichannel Silicon Drift Detector (SDD) based X-ray spectrometer with application-specific integrated circuit (ASIC) readout aimed at flying in future space missions. The multiple channels facilitate the spectrometer to have a large detection area, allowing the detection of faint X-ray sources. The spectrometer is designed to readout the signal from eight SDDs through a VErsatile Readout for Detector
Integration (VERDI) ASIC with high energy resolution in the 1-25 keV energy range. The spectrometer provides an X-ray spectrum for each detector simultaneously. Initially, the system is tested with five SDDs and shown that the spectrometer provides the energy resolution of ~148 eV at 5.9 KeV when SDDs are cooled to -35oC. We have also assessed the system’s performance for different detector operating temperatures and pulse shaping times. The detailed design and the performance assessment of the spectrometer will be presented in the seminar.
The Origin of Isotopes
Abstract
The origin of isotopes plays a cruicial role in understanding the chemical enrichment of the Universe. Isotopes are formed through nucleosynthesis processes in stars, including stellar burning, supernovae, and neutron star mergers. These processes distribute isotopes into the interstellar medium (ISM), influencing the evolution of galaxies. Galactic Chemical Evolution (GCE) provides a framework to model the production, distribution, and recycling of isotopes over cosmic time, driven by processes such as star formation, stellar feedback, and gas inflow/outflow.
In this seminar, I will discuss the primary sources of isotopes, the physics of their nucleosynthesis, and the mechanisms by which they are transported and mixed within galaxies. The talk will also explore the connection between isotope studies and the broader understanding of the Milky Way's formation and evolution.
A 3D Thermophysical model for Temperatures and Thermophysics at Prospective Sites on Mars
Abstract
Existing thermal models of Mars, such as the KRC 1D model, lack the ability to account for complex heat transport processes, topographical variations, and environmental factors like dust storms and surface changes. This study addresses these gaps by developing a 3D thermophysical model that integrates lateral heat transport, accurate topography from MOLA DEM, and Martian-specific conditions, including its thin CO₂ atmosphere and thermal inertia. The model provides detailed insights into localized thermal variations at prospective landing sites, enhancing mission planning and advancing our understanding of Mars' thermal behavior and geological history.
Mathematical Framework for Dust Dynamics under Different Forces
Abstract
Interplanetary Dust Particles (IDPs) are a fundamental constituent of the Solar System, originating from diverse sources such as the Asteroid Belt, Kuiper Belt, Oort Cloud, and comets. It manifests in phenomena like Zodiacal Light and Meteor showers. As IDPs migrate inward toward the Sun, their dynamics are governed by a combination of gravitational and non-gravitational forces, including Poynting-Robertson drag, solar radiation pressure, and solar wind drag, which induce perturbations in their orbital elements. In this seminar, I will discuss the mathematical framework for orbital perturbations and the governing force equations, derived from the principles of celestial mechanics. The variation in orbital elements due to the governing forces will be analyzed, along with the obtained results. In addition to this, the method for estimating the dust flux on planetary bodies will be explored, with a focus on insights derived from our research.