Clara Sousa-Silva

Detecting Biosignature and Pre-Biosignature Gases with Computational Chemistry

At the edge of our present scientific frontier lies the question: “How does life originate?”. Establishing how a planet becomes habitable, or inhabited, relies not just on the observation and interpretation of exoplanet atmospheres but also their stellar hosts and any planetary bodies, such as comets, that can deliver water and organic material to a planetary surface.

In turn, this interpretation of stellar spectra, planetary atmospheres, and comae, requires knowledge of the spectral behavior of every significant contributing molecule. However, though thousands of molecular candidates can contribute towards an astronomical spectrum, data exist for only a few hundred gases. Among these, only a fraction have complete spectra (e.g. ammonia, water). This deep incompleteness in the knowledge of molecular spectra presents a pressing vulnerability in the spectroscopic study of astronomical bodies; there exists a strong possibility of mis-assignment, false positives, and false negatives in molecular detections.

The work presented here combines structural organic chemistry and quantum mechanics to obtain the necessary tools for the interpretation of astrophysical spectra and, ultimately, the detection of biosignature, or pre-biosignature, gases. Whether life is associated with familiar gases (e.g. oxygen) or exotic biosignatures, painting a confident picture of a potential biosphere will require a holistic interpretation of an atmosphere and its molecules, and an understanding of their origin. In this talk I will describe the ongoing efforts to decipher astronomical atmospheres through the identification of volatile molecules, in particular those that might be associated with non-Earth-like life.