Spandan Dash

I was a PhD student in the Astronomy and Astrophysics group at the University of Warwick. My supervisor was Dr. Matteo Brogi. I am now a Postdoctoral Researcher at the Institute de Physique du Globe de Paris (IPGP) in Paris, France with a contract at Universite Paris Cite. I work in the group of Dr. Sebastien Charnoz on modelling volatile rich atmospheres above magma oceans. For any further updates, here is a link to my personal homepage.Link opens in a new window

Research focus during my PhD

I worked on characterizing sub-Jovian exoplanet atmospheres using high resolution spectroscopic data in the infra-red wavelength range from spectrographs mounted at some of the biggest telescopes on the planet e.g. VLT, TNG and CAHA. My overall research project was divided into observational and theoretical components.

Part - I (observational and computational)

My aim was to build a python pipeline to analyze data from atmospheres of giant and Neptune/sub-Neptune sized objects. The analysis of such data will aim at measuring their physical (temperature) and chemical (composition) properties which will serve to inform us of the diversity of gaseous planets that can exist and the kind of molecules that can be seen. This will then either match with predictions of theoretical atmospheric chemistry models or bring even more surprises and inform us about possible exotic chemical reactions that might make some specific molecules more or less abundant than expected.

Looking at the diversity of Neptune and sub-Neptune sized objects can also ultimately present an overview of the compositional diversity of atmospheres of such objects with the largest sampling frequency in exoplanet surveys. This will allow us to examine the dichotomy between the more gaseous and/or icy (similar to Neptune and Uranus) and the more terrestrial (rocky or water worlds similar to Earth or Mars) objects, which in turn has the potential to remove the degeneracy in composition that exists for such objects today. Efforts at characterization of atmospheres of such bodies at low resolution are often constrained by the fact that presence of clouds, hazes and aerosols in the atmosphere can result in flat spectra which obscures chemical signatures. High Resolution spectroscopy is expected to still be sensitive to species present above the cloud deck in such atmospheres. Hence, results from high resolution spectroscopic observations by taking cloud modelling, hazes and aerosols into account in our chemical models have the potential to make a massive contribution to understanding this class of exoplanets.

The Python pipeline I built for this purpose during my PhD (Dash et al. 2024) is called Upamana.

Part - II (theoretical and/or computational)

Planets similar to our own planet Earth are what excites us most since it directly addresses the ultimate question: Are we alone in the universe?

Keeping that question in view, the second part of my project was intended to venture into the simulation of observations of terrestrial exoplanet atmospheres, some of which will be/are expected to be close to our own planet’s conditions. As the ultimate goal of exoplanet research is to assess whether life exists elsewhere than the Earth, these simulations will inform the community on whether it is possible to use the next generation of giant telescopes - for instance the Extremely Large Telescope currently under construction in Chile - to recognise the imprint of biomarkers. Biomarkers are a set of molecules in the atmosphere which are thought to be indicators of biological life. In order to robustly claim their detection, the simulations will also explore whether it is possible to recognise and exclude false-positive scenarios (cases when one or more biomarkers are present in the atmosphere due to processes not related to life).

During my PhD, I built the Python pipeline Ratri (Dash et al. 2025), which can be used for simulation of transmission and emission observations of exoplanet atmospheres, at high spectral resolution, using some of the best current generation ground-based spectrographs. Together with Upamana, my PhD work thus resulted in the creation of an end-to-end mechanism to in order to quantify the high-resolution observability of specific molecular signatures in the atmosphere of any exoplanet (provided accurate ephemerides). The application of this end-to-end mechanism to quantify the detectability of diverse mineral atmospheres of the ultra-short period rocky exoplanet 55 Cnc e, dependent on the oxygen fugacity of the mantle, was done in Dash et al. 2025. Due to my PhD period coming to an end, I was not able to fully work on quantifying the detectability of biomarkers in terrestrial exoplanets, but I intend to do so in the future by extending this end-to-end mechanism to the next generation of ground-based spectrographs planned to be mounted on some of the largest telescopes currently being built (ELT, TMT and GMT).

Publications

Teaching

I served as a Senior GTA for the 1st year Physics and Electronics laboratory from 2021-2023.

Scholarship/Funding

I was a recipient of the Chancellor's International Scholarship provided by the University of Warwick.

Conferences, Workshops and Contributions

Seminars