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The search for life outside our solar system is at the forefront of modern astronomy, and telescopes such as the Habitable Worlds Observatory (HWO) are being designed to identify biosignatures. Molecular oxygen, O$_2$, is considered a…
We report 320 to 1020nm disk-averaged Earth reflectance spectra obtained from Moon's Earthshine observations with the EMMI spectrograph on the NTT at ESO La Silla (Chile). The spectral signatures of Earth atmosphere and ground vegetation…
Planetary surface habitability has so far been considered, in the main, upon a global scale. The increasing number of 3D modelling studies of (exo)planetary climate has highlighted the need for a more nuanced understanding of surface…
Here we review how environmental context can be used to interpret whether O2 is a biosignature in extrasolar planetary observations. This paper builds on the overview of current biosignature research discussed in Schwieterman et al. (2017),…
Dozens of habitable zone, approximately earth-sized exoplanets are known today. An emerging frontier of exoplanet studies is identifying which of these habitable zone, small planets are actually habitable (have all necessary conditions for…
To date, a handful of exoplanets have been photometrically mapped using phase-modulated reflection or emission from their surfaces, but the small amplitudes of such signals have limited previous maps almost exclusively to coarse dipolar…
The long-term habitability of Earth-like planets requires low orbital eccentricities. A secular perturbation from a distant stellar companion is a very important mechanism in exciting planetary eccentricities, as many of the extrasolar…
Finding life on exoplanets from telescopic observations is an ultimate goal of exoplanet science. Life produces gases and other substances, such as pigments, which can have distinct spectral or photometric signatures. Whether or not life is…
The James Webb Space Telescope and the future Habitable Worlds Observatory aim to discover exoplanet atmospheric spectra that detect life. Currently, most existing spectral "retrieval" algorithms focus on inferring the abundances of…
One of the great quests of astronomy is to obtain the spectrum of a terrestrial planet orbiting within the habitable zone of its star, and the dominant challenge in doing so is to isolate the light of the planet from that of the star.…
Planet Earth has evolved from an entirely anoxic planet with possibly a different tectonic regime to the oxygenated world with horizontal plate tectonics that we know today. For most of this time, Earth has been inhabited by a purely…
The ongoing searches for exoplanetary systems have revealed a wealth of planets with diverse physical properties. Planets even smaller than the Earth have already been detected, and the efforts of future missions are placed on the…
The next generation of high-contrast imaging instruments will provide the first unresolved image of an extrasolar planet. While the emitted infrared light from the planet in thermal equilibrium should show almost no phase effect, the…
Understanding the possible climatic conditions on rocky extrasolar planets, and thereby their potential habitability, is one of the major subjects of exoplanet research. Determining how the climate, as well as potential atmospheric…
The characteristics of irradiated solar system planetary atmospheres have been studied for decades, consequently modern planetary science benefits from an exhaustive body of ground- and space-based data. The study of extrasolar planetary…
We have investigated mid-infrared spectra of Earth obtained by the Atmospheric Infrared Sounder (AIRS) instrument on-board the AQUA spacecraft to explore the characteristics that may someday be observed in extrasolar terrestrial planets. We…
We use a probability theory framework to discuss the search for biosignatures. This perspective allows us to analyse the potential for different biosignatures to provide convincing evidence of extraterrestrial life and to formalise…
The strongest remotely detectable signature of life on our planet today is the photosynthetically produced oxygen (O2) in our atmosphere. However, recent studies of Earth's geochemical proxy record suggest that for all but the last ~500…
In the last few years astronomical surveys have expanded the reach of planetary science into the realm of small and dense extrasolar worlds. These share a number of characteristics with the terrestrial and icy planetary objects of the Solar…
Agriculture is one of the oldest forms of technology on Earth. The cultivation of plants requires a terrestrial planet with active hydrological and carbon cycles and depends on the availability of nitrogen in soil. The technological…