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School of Earth and Planetary Sciences
राष्ट्रीय विज्ञान शिक्षा एवंअनुसंधान संस्थान
National Institute of Science Education and Research

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Past Events

Understanding early Earth processes: A multidisciplinary approach
Date/Time:
Fri, 11/12/2021 - 19:00
Venue:
Online - Zoom
Speaker:
Dr. Priyadarshi Chowdhury
Affiliation:
Continents, plate tectonics and life make our Earth unique in the solar system and perhaps, in
the entire universe (so far). However, none of them was present when the planet formed some 4.56
billion years ago (Ga). Therefore, understanding how, when, and why they appeared is critical to
understand planetary evolution and habitability. My work directly deals with these questions. For the
past few years, I am working on elucidating in what form plate tectonics appeared on the early Earth
(> 2 Ga) and what imprints it left on the different system components of the planet (e.g., lithosphere,
mantle, atmosphere etc.). In the talk, I will show how I find answers to these questions by integrating
field geology and petrology with the novel methods like diffusion modelling of micron-scale
compositional zonings in minerals to unravel geological timescales (diffusion chronometry) and
numerical modelling of large-scale tectonics. My work has revealed that plate tectonics processes
were substantially different > 2 Ga from their modern nature and, for the first time, showed how
timescales of large-scale processes can help us identify it from the natural rock record. I proposed a
new style of continent-continent collision (called peel-back orogenesis) for that time period, which is
found to have major implications for building and recycling Archean continental crust. While I continue
to work on these aspects, I have further extended my research to understand how deep and shallow
Earth processes were linked in ‘deep time’ (> 3 Ga). My interest is to see how and why ‘continental dry
land’ formed since it is pivotal in controlling atmospheric and oceanic chemistry, and climate.
Modeling Solar-Stellar Astrophysical Plasma and Their Interaction with the Planetary-Exoplanetary Atmosphere
Date/Time:
Mon, 09/27/2021 - 06:30
Venue:
Online via zoom
Speaker:
Dr. Soumitra Hazra
Affiliation:

Space Physics, or Heliophysics, is the study of the medium between the Sun and the planets in our solar system, and the medium between stars and their planets. The space between stars and their planets is filled with a continuous flow of plasma, also called ''Solar/Stellar wind, and this outflow can impact the top of the atmosphere of planets on a short- and long range. Moreover, the interaction can be affected if the planet has an internal magnetic field. In my talk, I will review the modeling approach of solar and stellar wind. I will also discuss how the solar/stellar wind interacts with the planetary/exoplanetary atmosphere.

Lithospheric dynamics and geochemical cycles on Earth through time
Date/Time:
Wed, 09/22/2021 - 06:30
Venue:
Online via zoom
Speaker:
Dr. Vinod Oommen Samuel
Affiliation:
Earth is a dynamic planet, continuously undergoing geochemical cycling due to its internal and external thermal processes. Geochemical signatures of the interactions of Earth’s surface and its solid interior are imprinted on various rock types exposed in the planet’s solid outer layer, called the crust. Various rock types formed throughout Earth’s history are fortuitously preserved in the continental crust, in part due to lithospheric dynamics and its relatively lower density as compared to oceanic crust. The presence of an evolved continental crust, that preserves details of Earth’s history, makes Earth a unique planet in the solar system. In this talk, I present a broad overview of my study that shows how detailed field, petrological, geochemical and isotopic characteristics of various rock types can be used to improve our understanding of Earth’s history. Remnants of the continental crust (cratonic nuclei) that formed on early Earth still exist. For example, the Indian landmass is made up of five such cratons and their associated mobile belts. Of these, the lithological and geochemical variations that developed through the interactions of atmospheric, crustal and mantle components imprinted in the crustal blocks associated to the Dharwar Craton in southern India are significant. Interpreting and quantifying the lithospheric dynamics (e.g. plate tectonic and mantle interactions) and geochemical signatures additionally requires detailed comparative studies of various lithologies in different geologic settings in India and abroad. Such studies would also help us correlate tectonic settings in different parts of the world to improve our understanding of super-continental cycles through time. Furthermore, such projects could be extended to trace out mineralization zones for exploring elements important for the future energy industry.
Rivers in the Atmosphere: from Water Vapor to Aerosol Particles
Date/Time:
Fri, 09/17/2021 - 09:00
Venue:
Online via zoom
Speaker:
Dr. Sudip Chakraborty
Affiliation:

Ever since Zhu and Newell in 1994 identified that the filamentary river-like structures in the atmosphere transport a high amount of water vapor as high as the Amazon or the Mississippi River, there has been a growing interest in the scientific community to understand the role of the atmospheric rivers (AR) on rainfall, especially over the midlatitudes. ARs, covering only 5% of the earth area, transport over 90% of the moisture in the midlatitudes, are responsible for 90% of the flooding events, and contribute to a significant amount (40%) of freshwater supply in the U.S. Owing to ARs’ tremendous importance on the global climate, moisture transport, and precipitation, there have been many attempts to develop a detection algorithm to identify the ARs, both temporally and spatially- out of which, the algorithm, recently developed by Guan and Waliser (2015) has been the most successful one and widely-acclaimed in the scientific community. Leveraging the concept and importance of ARs on climate, it has also become necessary to investigate if such filamentary transports can be detected to other important constituents of the atmosphere like particulate matters or aerosols and gaseous pollutants that can have profound impacts on climate and air quality. Aerosols can influence climate through their interactions with clouds and precipitation, solar and infrared radiation, and also have adverse impacts on visibility and human health. Such influences are not confined to their source regions as aerosols and trace gases can be transported long distances, often across and between continents. Despite the strong impacts that aerosols and trace gases have on climate and air quality, significant gaps remain in our knowledge concerning their long-range transport, especially extreme transport events. With the above motivations in mind, this study introduces the extension and application of an already established AR detection algorithm (Guan et al., 2018; Guan and Waliser, 2015, 2019) to aerosols as a new and an alternative approach for understanding and quantifying aerosol transport extremes, hereafter referred to as “Atmospheric Aerosol Rivers” (AARs) using the Modern-Era Retrospective analysis for Research and Applications, Version 2 reanalysis (Chakraborty et al., 2021a). This presentation characterizes and quantifies various details of AARs that have never been studied before, such as AARs’ climatology, vertically integrated aerosol transport, seasonality, event characteristics, vertical profiles of aerosol mass mixing ratio as well as wind speed, and the fraction of total annual aerosol transport conducted by AARs. An analysis is also performed to quantify the sensitivity of AAR detection to the criteria and thresholds used by the algorithm.

Understanding Earth’s lithosphere dynamics 2 billion years ago
Date/Time:
Fri, 09/03/2021 - 03:00
Venue:
Online via zoom
Speaker:
Dr. Priyadarshi Chowdhury
Affiliation:

Continents, plate tectonics and life make our Earth unique in the solar system and perhaps, in the entire universe (at least, so far). However, none of them was present when  the planet formed some 4.56 billion years ago (Ga). Therefore, understanding how, when, and why they appeared is critical to understand planetary evolution and habitability. My work directly deals with these questions. For the past few years, I am working on elucidating in what form plate tectonics appeared on the early Earth (> 2 Ga) and what imprints it left on the different system components of the planet (e.g., crust-mantle, hydrosphere, atmosphere etc.). I find answers to these questions by integrating the classical approaches ofsolid Earth geology (field geology and petrology) with the novel methods like diffusion modelling of micron-scale compositional zonings in minerals to unravel geological timescales  (diffusion chronometry) and numerical modelling of large-scale tectonics (100s-1000s of km). So far, my studies have revealed that plate tectonics processes were substantially different > 2 Ga  from their modern nature and, for the first time, showed how timescales of large-scale processes can help us identify it from the natural rock record. In particular, I proposed a new style of continent-continent collision (called peel-back orogenesis) for that time period, which is found to have massive implications for building continents and driving the rise of O2 in the atmosphere.

Investigation of Interstellar Polycyclic Aromatic Hydrocarbon (PAH) molecules as carriers for mid-infrared emission bands
Date/Time:
Mon, 08/30/2021 - 03:00
Venue:
Online on Zoom
Speaker:
Dr. Mridusmita Buragohain
Affiliation:

Interstellar Polycyclic Aromatic Hydrocarbon (PAH) molecules exist in diverse forms depending on the local physical environment of the Interstellar Medium (ISM). Formation of ionized PAHs is favorable in the extreme condition of the ISM. Besides its pure form, PAHs are likely to exist in substituted forms, for example, PAHs with functional groups, nitrogenated PAHs, protonated and deuterated PAHs, etc. These PAHs may convert into alternate forms as a result of ongoing chemical processes in the ISM. The spectral evidence of PAH molecules and its variants in the ISM are observed via the mid-infrared emission bands, particularly at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.7 μm. These bands, also known as ‘Aromatic Infrared Bands (AIBs)’ are widely observed towards a varied range of astronomical sources and arise from the vibrational relaxation of PAH molecules on absorption of background UV photons. However, the exact form of PAH molecules that are responsible for the AIBs is still ambiguous. Here, we discuss a few of the possible forms of interstellar PAH molecules (for example: deuteronated, nitrogenated and aliphatic PAHs etc.) as carriers for AIBs. Density Functional Theory (DFT) calculation on several classes of PAHs is employed to study its spectral characteristics in infrared which is compared with the observed bands in quest of any similarity that establishes its presence in the ISM.

Retrieval of cloud/precipitation properties using satellite-based and ground-based radar & numerical models
Date/Time:
Fri, 03/12/2021 - 18:00
Venue:
Zoom Meeting
Speaker:
Dr. Shailendra Kumar
Affiliation:
An age-integrated mineral-chemical and geochemical investigations from the Bastar and the Bundelkhand cratons, Indian subcontinent and its implications in Precambrian supercontinent assembly
Date/Time:
Thu, 03/11/2021 - 18:00
Venue:
Zoom Meeting
Speaker:
Dr. Pritam Nasipuri
Affiliation:
Evolutionary response of shallow marine foraminifera to the extreme climate states of Cenozoic within the Indian subcontinent
Date/Time:
Wed, 03/10/2021 - 18:00
Venue:
Join Zoom Meeting
Speaker:
Dr. Sonal Khanolkar
Affiliation:
Aerosols and its interaction with the Indian summer monsoon
Date/Time:
Fri, 03/05/2021 - 18:00
Venue:
Online via zoom
Speaker:
Dr. Sushant Das
Affiliation:
Shock Effects in Meteorites and Laboratory Space Weathering Simulations
Date/Time:
Thu, 02/04/2021 - 20:00
Venue:
SEPS, Zoom Meeting
Speaker:
Dr. Surya Rout
Affiliation:
Studying Cool Exoplanets with Microlensing
Date/Time:
Tue, 02/02/2021 - 20:00
Venue:
SEPS conference room and online via zoom
Speaker:
Dr. Aparna Bhattacharya
Affiliation:
High-Pressure Studies of Oxides and Fluorides: Analogs for Ultra-High Pressure Behavior of Planetary Silicates
Date/Time:
Fri, 01/29/2021 - 19:30
Venue:
SEPS conference room and online via zoom
Speaker:
Dr. Rajkrishna Dutta
Affiliation:
Micro-and Nanoscale Study of Extraterrestrial Materials
Date/Time:
Tue, 01/26/2021 - 17:00
Venue:
SEPS conference room and online via zoom
Speaker:
Dr. Surya Rout
Affiliation:
Solar System like Exoplanets at Galactic Center
Date/Time:
Wed, 01/20/2021 - 18:00
Venue:
SEPS conference room and online via zoom
Speaker:
Dr. Aparna Bhattacharya
Affiliation:
High-Pressure Studies of Oxides and Fluorides: Analogs for Ultra-High Pressure Behavior of Planetary Silicates
Date/Time:
Mon, 01/18/2021 - 18:00
Venue:
SEPS conference room and online via zoom
Speaker:
Dr. Rajkrishna Dutta
Affiliation:
UV Light and Life in the Universe
Date/Time:
Mon, 10/12/2020 - 19:00
Venue:
Online
Speaker:
Dr. Sukrit Ranjan
Affiliation:

Abstract: The interaction of UV radiation with molecules (photochemistry) plays a key role in the surface-atmosphere system of rocky planets. In this talk, I will explore how photochemistry controls the chemical context in which life arose on Earth, and affects the molecular signposts with which we hope to detect life elsewhere. I will specifically discuss (1) photochemical insights into sulfur and nitrogen speciation in natural waters on early Earth, (2) the UV environment on planets orbiting Sunlike stars compared to M-dwarf exoplanets, and (3) the accumulation of potential biosignature gases in rocky planet atmospheres. I will connect each of these theoretical studies to empirical advances, such as the discovery of new pathways for prebiotic ribonucleotide synthesis, a possible opportunity to use exoplanets to test theories of the origin of life, and the recent discovery of phosphine on Venus. I will conclude by emphasizing the synergistic roles of experiment and theory.

Exoplanets and the Search for Habitable Worlds
Date/Time:
Tue, 07/28/2020 - 09:00
Venue:
Speaker:
Dr. Jayesh Goyal
Affiliation:
For centuries, humans have wondered about the existence of planets around stars, other than our own Sun. However, for the first time in human history we have the capability not just to find, but also to characterize these far away worlds, termed as “Exoplanets". In this talk I will show the astonishing variety of exoplanets that have been discovered and techniques used to find them. I will discuss how we study exoplanet atmospheres using the combination of remote sensing observations, 1D and 3D atmospheric models, retrieval techniques and thereby characterize them. I will also briefly discuss how modeling the atmospheres of exoplanets from first principles, aid in-depth understanding of different processes, in the past as well as present Earth. Finally, I will show our approach to answer one of the most fundamental questions of humanity, Are we alone in this Universe?
Melts and fluids in planetary systems
Date/Time:
Wed, 07/15/2020 - 09:30
Venue:
Speaker:
Dr. Shantanu Keshav
Affiliation:
Generation of melts (liquids/magmas) and fluids (e.g., gas), and their interactions in the Earth’s interior, are perhaps some of the most important of all planetary phenomena. Such activity is the principal mechanism by which planetary interiors differentiate chemically. The generally upward motion of magmas relative to solids can, and does, advect significant energy toward planetary surfaces.  Extrusion of magma on the surface and intrusion at shallow levels are the principal mechanisms by which planetary crusts form; these processes ultimately provide the raw material that is weathered, reworked, and remobilized by near-surface geologic processes; and in many cases, eruption of magma at the surface can have substantial nfluence on climate.
Here, from theoretical phase equilibria, thermochemistry, and experimental work, the most likely origin of magmas and fluids is discussed, with some focus on current/future work. On this aspect, fusion relations of the most plausible candidate materials (e.g., peridotite) with and without volatiles (for instance, water, H 2 O; carbon dioxide, CO 2 ), are examined in model systems as frameworks for visualizing, understanding, and analyzing igneous phenomena in more complex natural systems. Although these simple phase diagrams are incomplete models of actual magmatic systems, many of the processes that occur in natural systems can be understood by analogy with them, and most significantly, these phase diagrams often make it possible to visualize complex processes in relatively simple terms. Their staying power in earth-planetary sciences reflects the easy to understand yet powerful framework for interpreting and understanding complex natural phenomena that they provide.
On these bases, and without having misplaced notions tantamount to being presumptuous, some discussion, dominantly on fusion, derived on the basis of thermochemistry and experimental work, and how might it have “shaped” this planet, Earth, is presented. Attempt is made not to reach finalities, for such could be diagnosed as indicating my solipsism.
An Excursion in Laboratory Astrophysics: Large Carbonaceous Compounds
Date/Time:
Thu, 02/27/2020 - 11:00
Venue:
Speaker:
Dr. Shubhadip Chakraborty
Affiliation:
The interstellar medium (ISM) contains a plethora of various small and large organic molecules. Among the large organic molecules (PAHs) and fullerenes such as C60 and C70 are the main candidates. The presence of PAHs is revealed by the mid-infrared spectra of various astronomical objects, which comprise several broad emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 microns, called the aromatic infrared bands (AIBs). After 35 years of extensive research it has now been generally accepted that these bands arise from the infrared fluorescence of thermally excited PAHs of large size (50-100 C atoms) pumped by single FUV photon (Allamandola et al. 1985; Leger et al.1989). A similar process can be invoked for C60, which carries bands at 7.0, 8.5, 17.4 and 18.9 microns. Very recently, the diffuse interstellar bands (DIBs) at 9632 and 9577 Angstrom have been ascribed to the C60+ Campbell et al. (2015). It is interesting to mention that there are hundreds DIBs observed in the ISM and their carriers remain an enigma since 100 years. In the ISM, the processing of PAHs is driven by the interaction with stellar radiation, shock waves and cosmic rays. Berne & Tielens (2012) proposed that the formation of C60 is driven by the photolysis of large PAHs. On the other hand, Garcia-Hernandez et al. (2011) proposed that C60 could be formed from amorphous carbon due to shocks driven by fast stellar winds. In my talk I will demonstrate the use of laboratory astrophysics to solve some of the above questions. Experimental and theoretical IR spectroscopy of hot PAHs was performed Chakraborty et al. (2019) for an in-depth understanding of the carriers of AIBs and the physical state of cosmic C60 Joblin & hakraborty (2020). We also recorded the NIR spectrum of C60 at low temperature in the context of the identification of DIBs Chakraborty et al. (2020). Finally, I will show some experimental simulations of the evolution of interstellar dust analogues upon low velocity shocks.
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