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The initial composition and thermo-chemical state of a planet determine how its climate and geodynamics will evolve - for instance, whether the planet will have an internal magnetic field. These conditions are in turn a direct product of planet formation processes. My research focuses on two key areas: a) understanding primary planet formation processes, especially planetesimal formation and giant impacts, and how observations can help constrain theoretical models; b) exploring the sensitivity of key planetary properties (e.g., global magnetic field, style of mantle convection) to the initial state of the planet.
In order to assess how a planet’s geodynamics are affected by its initial conditions, I developed a new thermo-chemical framework for the Earth’s thermal evolution, core-mantle chemical interaction, and geodynamo [Mittal et al. 2019]. Using this framework, I demonstrated for the first time that mantle dynamics and composition control the rate of light element (e.g., Mg, Si, O) precipitation from the core. My analysis showed that this precipitation process can continuously generate a global magnetic field throughout Earth’s history. We are working on extending this to include various other elements (e.g., H,C,S) and couple with various surface observations to constrain Earth's interior evolution.
Mittal, T., Knezek, N., Arveson, S. M., McGuire, C. P., Williams, C. D., Jones, T. D., & Li, J. (2020). Precipitation of multiple light elements to power Earth's early dynamo. Earth and Planetary Science Letters, 532, 116030.
Work on Spectroscopy and Debris Disks (with extensions to Earth applications) :
My work has focused on theoretical and observational analyses of protoplanetary disks: coupled gas-dust dynamics during planetesimal formation [Mittal & Chiang 2015] and constraints on structure and composition of dust using infrared spectroscopy (with Christine Chen, Casey Lisse, Space Telescope Science Institute/APL) [Chen, Mittal et al. 2014; Mittal et al. 2015]. I used Spitzer IRS mid-IR spectroscopy to infer dust composition in debris disks - we used a combination of literature data as well as new programs to analyze >550 disks and do a comprehensive statistical analysis of dust composition [Chen et al. 2014; Mittal et al. 2014]. Using dust radiative transfer modeling and novel data analysis methods, I showed that many planetary systems have both an asteroid and a Kuiper belt, analogous to our solar system. My results also provided key observational constraints for the role of impacts during the accretion of rocky planets [Mittal et al. 2015].
I have active ongoing work to analyze this catalog as well as new spectroscopy datasets from JWST using an unsupervised ML algorithm - CLUES (CLustering UnsupErvised with Sequencer), a novel, non-parametric, fully interpretable machine-learning spectral analysis tool designed to analyze and classify the spectral data. This work was led by a co-supervised former graduate student - Cicero Lu as part of her NASA FINESST 2022 fellowship).
Ongoing work includes extending CLUES to various spectral datasets - both in planetary spectroscopy and various astrophysical datasets. In addition, we are using similar approaches, including supervised learning using Random Forest Classifiers, for Earth applications and optical spectral/hyperspectral data - the projects are focused on determining features of submarine volcanism (pumice raft, hydrothermal fluids) in satellite data (e.g., Sentinel-2, Landsat-8/9).
Selected Publications :
(i) The Spitzer infrared spectrograph debris disk catalog. II. Silicate feature analysis of unresolved targets, T Mittal, CH Chen, H Jang-Condell, P Manoj, BA Sargent, DM Watson; The Astrophysical Journal 798 (2), 87 25 2014
(ii) The Spitzer infrared spectrograph debris disk catalog. I. Continuum analysis of unresolved targets CH Chen, T Mittal, M Kuchner, WJ Forrest, CM Lisse, P Manoj, The Astrophysical Journal Supplement Series 211 (2), 25 22 2014.
(iii) Pumice Raft Detection Using Machine-Learning on Multispectral Satellite Imagery, Maggie Zheng, Tushar Mittal, Kristen Fauria, Ajit Subramaniam, Martin Jutzeler Front. Earth Sci., Sec. Volcanology 2022
(iv) Trends in Silicates in the β Pictoris Disk Cicero X. Lu, Christine H. Chen, B. A. Sargent, Dan M. Watson, Carey M. Lisse, Joel D. Green, Michael L. Sitko, Tushar Mittal, V. Lebouteiller, G. C. Sloan, The Astrophysical Journal 933, no.1 2022
(v) Sequencing Silicates in the IRS Debris Disk Catalog I: Methodology for Unsupervised Clustering, Cicero Lu, Tushar Mittal, Christine H. Chen, Alexis Y. Li, Kadin Worthen, B. A. Sargent, Carey M. Lisse, G. C. Sloan, Dean C. Hines, Dan M. Watson, Isabel Rebollido, and Joel D. Green Astrophysical Journal (in revision) 2024
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