Spectropolarimetric modeling of the Earth as an exoplanet, in search for new habitable worlds

Abstract

Previous studies have investigated the remote appearance of Earth-like exoplanets in the prospect of retrieving biosignatures of planets orbiting extrasolar stars, utilizing the variation of (polarized) flux. However, these studies did not use horizontally inhomogeneous models that include (1) daily cloud observations of planet Earth accounting for different cloud parameters with (2) an underlaying Earth-like surface cover, for (3) a set of wavelengths covering the ultra-violet, visible and near-infrared spectral domain. We present simulations of spatially resolved disks and planetary phase curves of the total flux, degree of polarization and linearly polarized fluxes. We discuss the presence of spectropolarimetric signatures that can potentially be directly retrieved from future observations. Moreover, in the design of future telescopes the characteristics of these signatures may be considered.

We conclude that utilizing a set of wavelengths in the visible and near-infrared domain, could potentially allow one to retrieve information about the presence, abundance and micro-physical properties of clouds in the atmosphere of, and also the presence of an ocean cover on, an Earth-like exoplanet.