Title : Planetary Differentiation and Sample Analysis

Abstract

After accretion from dust, gas, and rock colliding and sticking together, Planetary differentiation is the process by which a planet's molten materials separate into distinct layers. Following this early stage of planetary evolution, the differentiation process continues for billions of years and may still be ongoing today, owing to the internal dynamics of each planet. Over the past decade, planetary missions—especially to the Moon and Mars, as well as the growing number of recognized lunar and Martian meteorites — have provided transformational insights into the diversity, composition, and histories of planetary materials throughout the inner Solar System. Yet, despite these new insights, defining a reasonably simple set of criteria that provides some predictive understanding of planetary crustal development remains elusive. This talk will try to showcase the elusive characteristics of our understanding towards planetary evolution through the proxy of extra-terrestrial sample analysis.

Title : Coastal Groundwater: Effects of Climate Change and Abuse on a Critical Resource

Abstract

Groundwater is an essential resource for most coastal communities. Abuse of this resource and global sea level rise due to climate warming endanger its sustainability. In this talk, I will discuss less obvious aspects of changing coastal groundwaters. Along some coastlines, excess groundwater mining leads to land subsidence. Combined with global sea level rise, this causes enhanced coastal flooding and saltwater intrusion (SWI) into coastal aquifers. The intrusion of seawater into these aquifers poisons an essential resource. The movement is not one-way. Coastal aquifers are an underground link between the land and sea. Terrestrial freshwater and seawater are constantly mixed and exchanged within these permeable sediments, called subterranean estuaries. The flow of fresh or salty groundwater into the ocean is called submarine groundwater discharge (SGD). SWI radically alters the groundwater chemistry by introducing sulfate, a major ion in seawater and a powerful oxidizing agent. Fresh groundwater has low oxidation capacity due to the low solubility of oxygen. The sulfate in seawater brings 200 times greater oxidation capacity, allowing considerably more carbon to be oxidized. The byproducts of marine carbon oxidation include CO2, nutrients (N, P), sulfide (H2S), dissolved organic carbon and nitrogen, and reduced metals (Fe2+, Mn2+). SGD transports these byproducts of carbon oxidation into estuarine and coastal waters, where they may stimulate biological productivity – sometimes to excess, and deplete dissolved oxygen concentrations through reactions with sulfide and other reduced substances. My focus in this talk will be on the interplay between SWI and SGD and the effects on estuarine and coastal waters. About the speaker: Prof. Willard S. Moore is Distinguished Faculty Emeritus in the School of the Earth, Ocean and Environment at the University of South Carolina, USA. He is an internationally renowned marine geochemist whose pioneering research has transformed our understanding of coastal and oceanic processes through the application of naturally occurring radioisotopes, particularly radium isotopes. Prof. Moore’s work has been instrumental in quantifying submarine groundwater discharge and assessing its role in the transport of nutrients, trace metals, and carbon to the coastal oceans. Prof. Moore has been elected Fellow of both the American Geophysical Union (AGU) and the American Association for the Advancement of Science (AAAS), and is a recipient of the prestigious “Buck” Ketchum Award from the Woods Hole Oceanographic Institution.

Title : Exploring GRB Localisation Capability of Proposed Daksha Mission using Coded Mask Imaging with its Low-Energy Detectors and Their Development.

Abstract

Gamma Ray Bursts (GRB) are short, intense extragalactic gamma-ray flashes. GRBs are of two kinds-long GRBs (burst duration >2 sec) thought to be produced due to core collapse of rapidly rotating massive stars, short GRBs (duration <2 sec) believed to be produced due to merger of binary compact objects like neutron star-neutron star (NS-NS) or black hole-neutron star (BH-NS). Daksha is India’s proposed high-energy transient mission aimed at detecting and characterizing electromagnetic counterparts (EMCs) of gravitational wave (GW) events and GRBs. In its initial configuration, Daksha can localize short GRBs to within 5–10 degrees using a projection method. Daksha’s scientific potential could be greatly enhanced if onboard GRB localization within 1 degree is made possible, which can be potentially achievable using the Coded Aperture Mask (CAM).

Title : Multi-wavelength Variability and Quasi Periodic Oscillations (QPOs) in Blazars

Abstract

This is the age of multi-wavelength (MW) time domain astronomy in which the transient astronomical sources are of great interest due to their rapid change in flux, spectra and polarization. Simultaneous MW observation of a particular transient source over an extended period of time has importance to understand the emission mechanism in different electromagnetic (EM) bands. Blazars are among one of the most favourite astronomical transient objects, because they emit radiation in the complete EM spectrum, and their flux, spectra and polarization are highly variable.

Title : Interplanetary Dust and Its Measurement in Solar System

Abstract

Our solar system is immersed in a thin cloud of Interplanetary Dust Particles (IDPs). The dust is an important constituent in formation of solar system and found everywhere. The IDP may originate from sources like Asteroid belt, Kuiper belt or comets and evolve dynamically under the influence of various forces. Although, there are some measurements of IDP near Earth and also, in the interplanetary space; there are no measurements of IDP at other inner planets. The entering dust particles in a planetary object can affect it in different ways. During the seminar, the results of IDP flux in inner solar system will be presented. The Dust EXperiment (DEX) was flown recently using POEM 3 on PS4 of PSLV C-58 (XPoSat) mission to understand dust particles in the Earth orbit. From the dust observations in near Earth orbit, the DEX was found working successfully in space. The results obtained from DEX will be also be presented

Title : Role of picophytoplankton in the carbon cycle of the northern Indian Ocean

Abstract

Picophytoplankton are vital drivers of marine biogeochemical cycles and serve as indicators of ocean productivity, ecosystem health, and climate change. As the smallest single-celled phytoplankton, they play a crucial role in ocean ecosystems, being globally recognized as major primary producers and significant contributors to the oceanic carbon stock. Despite their ecological importance, their role is often underestimated, particularly in the northern Indian Ocean—an oceanic region characterized by high environmental variability and dynamic biogeochemical processes. In this seminar, I will present the results that aimed to quantify the abundance and carbon biomass of picophytoplankton and to assess the influence of regional physicochemical parameters on their spatial distribution and ecological role in the northern Indian Ocean. Our findings demonstrate that the contribution of picophytoplankton carbon biomass to the total particulate organic carbon (POC) pool was substantial in both the Arabian Sea and the Bay of Bengal. This underscores their significant, yet often overlooked, role in supporting the regional biological pump and influencing carbon fluxes.

Title : Investigating Lunar Subsurface Water Ice through Neutron Leakage and Gamma-Ray Continuum Flux

Abstract

Lunar volatiles, including water ice, are considered to be preserved in cold traps or buried beneath the surface layer near the poles. Understanding their distribution and abundance is critical for advancing knowledge of lunar evolution and for supporting future exploration activities. Neutron and gamma-ray spectroscopy provide key tools for this purpose, as subsurface hydrogen abundance can be inferred to depths of up to 1 m from measurements of neutron leakage flux and gamma-ray continuum flux from the Moon. In this seminar, I will discuss the lunar leakage neutron and gamma continuum flux induced by galactic cosmic rays interacting with the lunar surface, as well as their dependence on subsurface hydrogen abundances, using Monte Carlo simulations. The effects of temperature and compositional variation on neutron leakage flux are examined. The sensitivity of the leakage neutron intensity to the depth profile of subsurface water ice within the top 1 m of soil will also be discussed.