From exo-Earths to exo-Venuses: Flux and polarization signatures of reflected light

Context. Terrestrial-type exoplanets in or near stellar habitable zones appear to be ubiquitous. It is, however, unknown which of these planets have temperate, Earth-like climates or for example, extreme Venus-like climates. Aims. Technical tools to distinguish different kinds of terrestrial-type planets are crucial for determining whether a...

Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory

NASA is engaged in planning for a Habitable Worlds Observatory (HabWorlds), a coronagraphic space mission to detect rocky planets in habitable zones and establish their habitability. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can...

Ocean signatures in the total flux and polarization spectra of Earth-like exoplanets

ontext. Numerical simulations of starlight that is reflected by Earth-like exoplanets predict habitability signatures that can be searched for with future telescopes.<br/><br/>Aims. We explore signatures of water oceans in the flux and polarization spectra of this reflected light.<br/><br/>Methods. With an adding-doubling algorithm, we computed...

Exoplanet cartography using convolutional neural networks

Context. In the near future, dedicated telescopes will observe Earth-like exoplanets in reflected parent starlight, allowing their physical characterization. Because of the huge distances, every exoplanet will remain an unresolved, single pixel, but temporal variations in the pixel’s spectral flux contain information about the planet’s surface...

Biosignatures of the Earth: I. Airborne spectropolarimetric detection of photosynthetic life

Context. Homochirality is a generic and unique property of life on Earth and is considered a universal and agnostic biosignature. Homochirality induces fractional circular polarization in the incident light that it reflects. Because this circularly polarized light can be sensed remotely, it can be one of the most compelling candidate...

Colors of an Earth-like exoplanet: Temporal flux and polarization signals of the Earth

Context. Understanding the total flux and polarization signals of Earth-like planets and their spectral and temporal variability is essential for the future characterization of such exoplanets. Aims. We provide computed total (F) and linearly (Q and U) and circularly (V) polarized fluxes, and the degree of polarization P of sunlight that is...

PyMieDAP: A Python-Fortran tool for computing fluxes and polarization signals of (exo)planets

PYMIEDAP (the Python Mie Doubling-Adding Programme) is a Python-based tool for computing the total linearly and circularly polarized fluxes of incident unpolarized sunlight or starlight that is reflected by solar system planets or moons, respectively, or by exoplanets at a range of wavelengths. The radiative transfer computations are based on...

Circular polarization signals of cloudy (exo)planets

The circular polarization of light that planets reflect is often neglected because it is very small compared to the linear polarization. It could, however, provide information on a planet’s atmosphere and surface, and on the presence of life, because homochiral molecules that are the building blocks of life on Earth are known to reflect...

Polarized scattered light from self-luminous exoplanets: Three-dimensional scattering radiative transfer with ARTES

Context. Direct imaging has paved the way for atmospheric characterization of young and self-luminous gas giants. Scattering in a horizontally-inhomogeneous atmosphere causes the disk-integrated polarization of the thermal radiation to be linearly polarized, possibly detectable with the newest generation of high-contrast imaging instruments....

Flux and polarization signals of spatially inhomogeneous gaseous exoplanets

Aims. We present numerically calculated, disk-integrated, spectropolarimetric signals of starlight that is reflected by vertically and horizontally inhomogeneous gaseous exoplanets. We include various spatial features that are present on Solar System’s gaseous planets: belts and zones, cyclonic spots, and polar hazes, to test whether such...