Biosignature Detection in Exoplanetary Atmospheres Using Monte Carlo Simulations
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Date
2021-05
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The Ohio State University
Abstract
Development is under way of an exoplanetary atmosphere simulator GEANT4-ExoPlanets (GEANT4-ExoP) based on the multi-purpose Monte Carlo program package GEANT4, which enables modeling transmission of radiation and particles through matter. GEANT4-ExoP will provide a toolkit to model the transmission of host-star radiation through differentiated atmospheric layers using radiative transition data for a plethora of atoms and molecules. GEANT4-ExoP will allow observations to be compared with simulated spectra, demystifying atomic and molecular abundances in exoplanetary atmospheres. We focus on biosignatures such as H, C, N, O, P, and S atoms and molecules comprised of them. The Sun-Earth system will be fully simulated first as a test case with a focus on modeling absorption and emission spectral features. With the data filtered through GEANT4-ExoP, we report Gaussian convolutions of the Kurucz simulated solar irradiance and flux residual spectra. Precise atomic radiative transmissions are calculated using SUPERSTRUCTURE (SS), a program package that computes atomic energies, probabilities, and opacities. Sample results of spectroscopic diagnostic lines for PXIV are reported, with their values being compared to NIST values and other published results, ensuring accuracy and precision. Transition probabilities for biosignature molecules are obtained through collaboration with the EXOMoL team at the University of College London. Calculations will be conducted for many atoms and integrated into GEANT4-ExoP following assurance of accuracy. Current work is dedicated to developing the module to generate monochromic opacity profiles for each atom and molecule. GEANT4-ExoP will provide a toolkit for the modeling of host-star radiation transmission through exoplanet atmospheres, allowing for assessment of habitability and characterization of biosignature abundances within observations.
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Keywords
exoplanet, spectroscopy, Monte Carlo, simulation, biosignature, Geant4