Planetary Sciences Seminars

Our solar system formed ca. 4,567 Ma ago from the collapse of a dense core within an interstellar molecular cloud. Determining the timescales (chronological studies) of the accretion of planetesimals that later formed the terrestrial planets and asteroids, and linking this information to the source reservoirs of their precursor materials (genealogical studies), are key to understanding the temporal and spatial constraints on early solar system processes. Meteorites, rocks that formed during the early stages of the solar system and made their way to Earth, are our most powerful means to retrace the formation, transport, and evolution of early planetesimals at different times and locations within the protoplanetary disk and beyond. They sample various asteroids, the Moon, and Mars, and are the most accessible source of extraterrestrial matter for direct study in the laboratory. This presentation discusses the chronology and genealogy of various solar system materials using high-precision Cr isotopes as chronological and genealogical tools. These studies are based on the determination of radiogenic and nucleosynthetic Cr isotope variations in meteorites and terrestrial impactites with meteoritic contamination

The Archean Dharwar Craton of southern India preserves volcano-sedimentary greenstone belts that record early Earth crustal evolution, tectonic processes, and ocean–atmosphere chemistry. The Dharwar Craton hosts well-preserved Banded Iron Formations (BIFs) within volcano-sedimentary greenstone belts. Integrated field observations, mineralogical analyses, and whole-rock major, trace, and rare earth element (REE) geochemistry of the BIFs (spanning ~3300–2600 Ma) reveal distinct paleoenvironmental signatures. Low total REE contents, positive Eu anomalies, and characteristic trace-element ratios indicate a dominant hydrothermal source for iron, and the variable Ce anomalies suggest fluctuating redox conditions in the Archean ocean–atmosphere system. Variations in mineral facies and Fe–Si systematics, together with localized enrichment in Al₂O₃ and CaO, reflect basin-scale heterogeneity and minor detrital input during BIF deposition. Building on these findings, future research will extend these mineralogical and geochemical approaches to planetary environments, particularly Mars. Comprehensive studies of the characteristics of terrestrial hematite are necessary to establish a basis for understanding hematite found on Mars, since sample return from Mars is still a distant prospect. Additionally, hematite, a major iron oxide phase in BIFs, is also a key indicator of aqueous activity, oxidation processes and habitability on Mars. By integrating hematite from diverse geological settings on Earth, particularly from the Indian geological record, this work aims to establish robust terrestrial analogues for Martian hematite formation, providing new insights into oxidation processes, validation of rover-based data and the evolution of early Martian surface environments.

The dayside ionosphere of Venus exhibits a recurring electron density enhancement known as the "topside bulge". It has been reported by multiple missions, yet its formation mechanisms remain debated. Using over 200 dayside electron density profiles from the Venus Radio Science experiment (VeRa) onboard Venus Express (2006–2014), we classify bulges into three types using an automated, gradient-based method. Type 1 bulges are found at higher altitudes, whereas Type 2 and Type 3 bulges occur at comparatively lower altitudes within the photochemistry-dominated region above the V2 layer. In this seminar, after discussing the morphological differences and occurrence rates of these bulge types, I will demonstrate the necessity of correcting for solar flux at Venus by accounting for both heliocentric distance and solar rotation in order to accurately characterize the primary V2 layer. Using the built-in house 1D photochemical model, I will discuss how vertical variations in electron temperature influence the structure of the topside ionosphere and shape the observed bulge morphology within the photochemically dominated regime.

Asteroidal materials contain diverse organic matter (OM) components that are heterogeneously distributed within their mineral matrices. Organic matter occurs as either soluble organic matter (SOM) or insoluble organic matter (IOM). IOM is a complex macromolecular polymer spanning nanometer- to micrometer-scale, whereas SOM consists of relatively simple organic compounds bearing functional groups and is extractable using solvents such as water, methanol, and dichloromethane. Due to its insoluble nature, IOM can be characterized using petrographic, surface, and bulk analytical techniques, while SOM is primarily accessible through bulk molecular and isotopic analyses. My PhD research focused on the systematic characterization of IOM through the development of a novel SEM–EDS–based workflow integrating image processing and machine learning, which enabled unbiased identification of two distinct organic phases: concentrated organic matter (COM) and diffuse organic matter (DOM). COM exhibits petrographic properties analogous to classical IOM in terms of contrast, size, and spatial distribution, whereas DOM displays distinct characteristics. Based on these observations, I hypothesize that DOM may represent the petrographic expression of SOM within the matrix. To test this hypothesis, I propose to extend this work to direct SOM characterization at PRL by extracting SOM from sample aliquots and analyzing its molecular, spectral, and isotopic properties using FTIR, Raman spectroscopy, and NanoSIMS. Comparative isotopic analyses of aliquots before and after SOM extraction will be used to assess the contribution of SOM to the overall isotopic signature. Confirmation of this hypothesis would suggest distinct accretion sources for SOM and IOM, whereas its rejection would imply multiple sources or temporal variations in organic matter accretion within carbonaceous chondrite parent bodies.

Impact cratering exerts a primary control on the geological evolution of planetary bodies and serves as a key proxy for relative chronology, resurfacing processes, and crustal modification. Although major crater catalogs exist for the Moon and Mars, completeness declines at smaller diameters where manual mapping becomes laborious and observers differ in detection thresholds. Automated crater detection pipelines have advanced substantially with the introduction of classical machine learning, deep convolutional detectors, transformer-based architectures, and fusion of optical imagery with topography. These approaches improve recall for small and degraded craters, and support near-real-time inference, with potential utility for crater size–frequency distribution studies, surface chronology, and terrain-relative navigation. Building on these developments, the South Pole–Aitken Basin provides an exceptional natural laboratory for probing deep lunar lithologies. Multiple lines of evidence suggest that the SPA-forming impact may have excavated crustal and possible mantle materials, enabling investigation of Lunar Magma Ocean differentiation, the distribution of pyroxene and olivine lithologies, and the presence or depletion of KREEP during early lunar evolution. The proposed research integrates hyperspectral, geochemical, and contextual datasets with supervised and deep learning classification to evaluate mantle signatures at SPA, assess their geological context, and quantify implications for crust–mantle stratigraphy. The expected outcomes are relevant to lunar science priorities including landing site characterization, sample return targeting, and comparative studies of early solar system impact environments.

Oxygen and carbon are among the most abundant elements in the universe, forming the molecules that shape the environments of planets, comets, and interstellar space. However, the observed gas-phase abundances of oxygen- and carbon-bearing species in dense molecular clouds and cold regions of protoplanetary disks are significantly lower than predicted. This discrepancy suggests that much of these elements is trapped in icy mantles on dust grains. The structure of these icy mantles, whether crystalline, nonporous amorphous, or porous amorphous, plays a critical role in how molecules adsorb, diffuse, and desorb, yet the underlying surface processes remain poorly understood. This study employs ultra-high vacuum laboratory experiments using Reflection Absorption Infrared Spectroscopy (RAIRS) and Temperature Programmed Desorption (TPD) to investigate molecular interactions with interstellar ice analogues. RAIRS will be used to probe hydrogen bonding, molecular orientation, and structural changes, while TPD will quantify desorption kinetics and binding energies. By systematically exploring the relationship between molecular chemistry and ice morphology, this research aims to clarify the processes of retention and release of key oxygen- and carbon-bearing species.

Observed cometary production rates are often treated as straightforward measures of activity, but in practice they depend strongly on the physical characteristics of the nucleus. Properties such as shape, rotation state, and illumination conditions can change how much of the surface is effectively active at different points along the orbit. As a result, variations in production rates do not necessarily reflect changes in composition or heliocentric distance alone. In most research work spherical shape and uniform activity is taken to model the nuclues which can mask important physical effects and lead to misleading interpretations of outgassing behavior. In this seminar, I will explore how nucleus geometry and orientation influence observed production rates and discuss why more realistic representations of cometary nuclei are needed to better link observations with the physical state and evolution of comets.

Nightside aurorae at Mars are produced when electrons precipitate into the upper atmosphere generating photon emissions. The Emirates Mars Mission (EMM) provides full-disk far-ultraviolet imaging with Emirates Mars Ultraviolet Spectrometer (EMUS), revealing three discrete aurora types: crustal field aurora, patchy aurora, and sinuous aurora. Concurrent in-situ MAVEN observations confirm that supra-thermal electron flux enhancements (less than 1 keV) drive elevated nightside ionospheric densities and auroral emissions. Electron pitch-angle distributions indicate precipitation along open magnetic field lines, characterized by field-aligned electron flow. During a conjunction event, EMUS and MAVEN data show that sinuous aurora correlate with magnetotail current sheet. Based on their attributes, sinuous aurora appears to be a projection of the tail current sheet under conditions which allow energized electrons to populate it. The current sheet itself is a persistent yet highly variable feature of Mars’ double-lobed magnetotail resulting from the draping of the IMF around the Martian ionosphere.

Dust is ubiquitous in the Martian environment and plays a vital role in atmospheric dynamics and seasonal variability. Near the surface, dust devils and dust storms are frequently observed, particularly during the southern hemisphere summer, with some dust storms growing to regional or even global scales. Dust devils are convective vortices which are formed because of the temperature inversions in between the surface and the nearby atmosphere. Within these vortices, intense dust lifting and collisions lead to significant charge separation through triboelectric processes. As a result of charge separation and low atmospheric conductivity on Mars, there is a possibility for electrical discharge to occur. In this seminar, I will be giving an overview of the existing models and some of the preliminary results which supports the electrical discharge in Martian environment.

Martian meteorites, together with rover and orbital observations, provide crucial information about the geological evolution of Mars. These meteorites provide evidence of early planetary differentiation, long-lived magmatism, mantle heterogeneity, and water–rock interaction. In this talk, I will discuss the classification of Martian meteorites and summarise the current understanding of Martian geology derived from their geochemical and isotopic characteristics. I will also highlight the major gaps in our understanding of Martian magmatic processes and compositional diversity and discuss how future studies can help address these unresolved questions.

The Moon is covered with several meters of thick layers of unconsolidated debris having variable thickness on the Maria and Highlands regions overlying more intact strata called the lunar regolith. Knowledge of the physical properties of  lunar regolith is essential for both science and exploration of the Moon. The present understanding about the regolith properties primarily come from onboard experiments and returned samples from Apollo and Surveyor, limited to only equatorial latitudes. Regolith characteristics at other different locations, in particular the high-latitudes and poles are not known. In this talk,  I will discuss about the current understanding of the physical properties of lunar regolith—specifically its geotechnical, thermophysical, and elastic characteristics—and assess their implications for future lunar exploration. By integrating these multidisciplinary parameters, I will highlight how a deeper understanding of lunar regolith is essential to support science, safe landing operations,  in-situ resource utilization and habitat design, in future. I will also briefly discuss the critical knowledge gaps that require future measurements to enable sustained human presence on the Moon.

Lunar swirls are enigmatic, high-albedo, sinuous surface features unique to the Moon and co-located with prominent crustal magnetic anomaly regions. Although the lunar swirls are widely studied, their formation process remains unclear. In this seminar, I will introduce lunar swirls and the three competing hypotheses proposed to explain their formation mechanism: solar wind shielding, cometary impact scouring, and electrostatic dust transfer. The advantages and limitations of each hypothesis will be discussed, with a specific focus on modeling attempts related to the solar wind shielding mechanism. While the model has advanced significantly, it predominantly focuses on reproducing the specific features of Reiner Gamma. Consequently, this seminar highlights the necessity of extending the model to other lunar swirls to determine whether a single mechanism is sufficient or if a mutual integration of mechanisms is required.

The Freundlich-Sharonov Basin, ~600 km in diameter, is a pre-Nectarian/Nectarian basin located on the farside of the Moon at 18.35°N, 175.2°E. The presence of this highly degraded basin was first confirmed by the Clementine altimetry data and the recent gravity observations from the GRAIL mission revealed the presence of two rings associated with the Freundlich-Sharonov Basin. Unlike many lunar basins that are completely filled with mare emplacements, the Freundlich-Sharonov Basin exhibits only a limited distribution of the dark-toned materials confined within the central portion of the basin. Several studies have previously investigated these dark-toned materials but there is no clear consensus on their origin and mode of emplacement. While some studies interpret these dark-toned materials as remnants of an impactor, others suggest a pyroclastic origin or attribute their presence to localized mare volcanic activity. In this seminar, I will present a detailed study of the Freundlich-Sharonov basin incorporating insights from morphological, chronological and compositional analysis using a variety of datasets from missions such as Chandrayaan, Kaguya, and LRO. The results from this work enhance our understanding of the volcano-tectonic evolution of the Freundlich-Sharonov Basin and will have implications to decipher the geological evolution of similar large impact structures on the Moon.

The Venusian ionosphere has been studied for several decades using
various instruments, with radio science experiments providing some
of the most detailed insights. While the basic ionization processes
are well understood, the coupling between the lower ionosphere and upper
atmosphere, along with the variability near the ionopause region, remains
only partially understood. Recent findings and improved retrieval
techniques are now offering clearer perspectives on these interactions and
helping to refine our understanding of Venus’s plasma environment. This
presentation will demonstrate how modern radio science is transforming our
understanding of planetary ionospheres and the future of exploration.

Since the discovery of the first exoplanet, the field of exoplanet studies has expanded rapidly. With the current census of confirmed exoplanets exceeding 6,000, the “zoo” of known worlds now spans a vast range of planets, from “hot Jupiters” with orbital periods of less than a day to cold, ocean-covered “mini-Neptunes.” The scientific frontier is now shifting from mere detection to the detailed characterisation of exoplanet atmospheres. This seminar provides a basic overview of exoplanets, beginning with the fundamental challenges that make direct observation difficult. We will also discuss two indirect observation methods—transit photometry and radial velocity—and how they constrain the mass and radius of exoplanets. The focus of the seminar will be the characterisation of exoplanetary atmospheres using an extension of the transit photometry method: transit spectroscopy. To interpret these complex spectra, we employ “atmospheric retrieval,” a computational method that uses forward models and Bayesian inference to statistically derive atmospheric properties such as mixing ratios and vertical structure. An atmospheric model is critical in this process. Finally, the seminar addresses the limitations of standard chemical-equilibrium models. While simple to compute and sufficiently accurate for hot planets, these models often fail to represent atmospheres where chemical-reaction timescales are long. This highlights the need for disequilibrium models, and I will showcase one example of such models.

The thermophysical environment of the Moon plays a crucial role for future exploration, resource utilization & in understanding its geological evolution. While global surface temperatures are available, only a limited understanding exist about the local scale temperature environment and thermophysical characteristics due to less samples and in situ experiments. In view of several missions planned for future lunar exploration, it is imperative to have an improved understanding of the temperatures and thermophysical environments of key sites on the Moon. We have carried out an in-depth analysis of lunar surface thermal environment across several distinct and scientifically important sites on the Moon. We have used ~15 years of observations from Diviner lunar radiometer to generate improved 3D temperature maps at all the selected sites, using a rigorous and refined methodology. In this talk, I will discuss the methodology, characterisation and interesting results from the study.

Since 2013 the Geoforschungszentrum in Potsdam has operated a Cameca 1280-HR large geometry Secondary Ion Mass Spectrometer. This large-scale infrastructure is at the heart of an open user facility that supports the research needs of geoscientist from around the globe. The key capability of this instrument is its ability to perform precise analyses on sample masses reaching down into the picogram mass range; access to such micron-scale sampling is often essential for many geoscience applications. The work of the Potsdam SIMS lab falls into three general categories: the determination of light stable isotope ratios, U-Pb geochronology and the production of new microanalytical reference materials that are intended for world-wide distribution. During this talk I will describe the operation of our facility and will highlight a few examples of our research output.