Planetary Group Seminar: Polarization Spetra of Planet Earth (M. Sterzik)

Polarimetry is routinely used as a diagnostic tool to characterize surfaces of solar system bodies, and polarization measurements of starlight reflected by exoplanets are becoming a powerful tool to study atmospheres and surfaces of other worlds. If extra-terrestial life has similar signatures as life as we know, then astronomical observations of planet Earth represent a prime benchmark case to probe biomarkers on other planets. In fact, linear polarization spectra of Earthshine (the sunlight that has been first reflected by Earth and then reflected back to Earth by the Moon) allows us to detect the presence of oxygen, ozone, and clouds in the atmosphere of our planet. Surface properties such as fractional contributions of continents and ocean, as well as vegetated areas can be inferred. Earthshine observations provide strong observational constraints on model predictions for Earth-type exoplanets. In this talk, we will compare observed polarization spectra with detailed simulations of Earthshine based on atmosphere models, and will discuss their applications to the search for life indicators in exoplanets.