MOLECULAR SIMULATIONS FOR THE SPECTROSCOPIC DETECTION OF BIOSIGNATURE GASES AND OTHER VOLATILES

Unambiguously identifying molecules in spectra is of fundamental importance for a variety of scientific and industrial uses; a compelling modern focus is the spectroscopic detection of volatiles in exoplanet atmospheres, and the assessment of habitability and inhabitability of these planets.

Analyses of observational spectra require information about the spectrum of each of its putative components. However, spectral data currently only exist for a few hundred molecules and only of fraction of those have complete spectra (e.g. H2O, NH3). Consequently, molecular detections in exoplanet atmospheres are vulnerable to false positives, false negatives and miss-assignments (Sousa-Silva+ in prep). There is a key need for spectral data for a broad range of molecules.

Using a combination of experimental measurements, organic chemistry, and quantum mechanics, ATMOS (Approximate Theoretical MOlecular Spectra) is a programme that: 
a)    Provides approximate spectral data (band centres and relative intensities) for molecules in seconds, including thousands of potential biosignature gases (Seager+2016).
b)    Assesses hundreds of molecules simultaneously, highlighting patterns and any distinguishing features. Traditional methods for obtaining spectra are extremely costly and time-consuming (i.e. months/years per molecule); ATMOS will inform prioritization protocols for future high accuracy studies.
c)    Demonstrates that, at low resolution, individual spectral features could belong to a large number of molecules. Molecular detections in spectra are often made by assigning one, or a few, spectral features to a given molecule. ATMOS can highlight ambiguities in such molecular detections and also direct observations towards spectral regions that reduce the degeneracy in molecular identification.

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