Planetary atmospheres and chemical markers for extraterrestrial life

Abstract

A decade of exoplanet research has led to surprising discoveries, from giant planets close to their star, to planets orbiting two stars, all the way to the first hot, confirmed rocky worlds with potentially permanent lava on their surfaces due to the star’s proximity. Observation techniques have reached the sensitivity to explore the chemical composition of the atmospheres as well as physical structure of some detected exoplanets and to detect planets of less than 10 Earth masses (MEarth) and 2 Earth radii, so called Super-Earths, among them some that may be habitable. To characterize a planet’s atmosphere and its potential habitability, we explore absorption features in the emergent and transmission spectra of the planet that indicate the presence of biology. This Chapter discusses our strategy to characterize rocky exoplanets remotely, the basics underlying the concept of the Habitable Zone as well as chemical markers that indicate life through geological time.