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Oxygen is a well-studied biosignature. Studying potential abiotic pathways for O2 build-up in exoplanet atmospheres is essential for evaluating whether the detection of O2 would constitute a biosignature detection on other worlds. Previous…
Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is…
The search for life on planets outside our solar system will use spectroscopic identification of atmospheric biosignatures. The most robust remotely-detectable potential biosignature is considered to be the detection of oxygen (O_2) or…
Here we advocate an observational strategy to help prioritize exoplanet observations. It starts with more easily obtained observational data, and ranks exoplanets for more difficult follow-up observations based on the likelihood of avoiding…
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),…
In the search for life on Earth-like planets around other stars, the first (and likely only) information will come from the spectroscopic characterization of the planet's atmosphere. Of the countless number of chemical species terrestrial…
As oxygen is essential for respiration and metabolism for multicellular organisms on Earth, its presence may be crucial for the development of a complex biosphere on other planets. And because life itself, through photosynthesis,…
Previous research has indicated that high amounts of ozone (O3) and oxygen (O2) may be produced abiotically in atmospheres with high concentrations of CO2. The abiotic production of these two gases, which are also characteristic of…
Life has had a dramatic impact on the composition of Earth's atmosphere over time, which suggests that statistical studies of other inhabited planets' atmospheres could reveal how they co-evolve with life. While many evolutionary pathways…
Ozone is a potential biosignature and disambuguator between Earth-like and Venus-like exoplanets due to its association on Earth with photosynthetically produced oxygen (O$_2$). However, the existence of ozone in Venus's observable…
In the next decades, the astrobiological community will debate whether the first observations of oxygen in an exoplanet$'$s atmosphere signifies life, so it is critical to establish procedures now for collection and interpretation of such…
Thousands of planets beyond our solar system have been discovered to date, dozens of which are rocky in composition and are orbiting within the circumstellar habitable zone of their host star. The next frontier in life detection beyond our…
The oxidation of rocky planet surfaces and atmospheres, which arises from the twin forces of stellar nucleosynthesis and gravitational differentiation, is a universal process of key importance to habitability and exoplanet biosignature…
We investigate the abiotic production of oxygen and its photochemical byproduct ozone through water vapor photolysis in moist atmospheres of temperate terrestrial exoplanets. The amount of water vapor available for photolysis in the middle…
Spectral characterization of Super-Earth atmospheres for planets orbiting in the Habitable Zone of M-dwarf stars is a key focus in exoplanet science. A central challenge is to understand and predict the expected spectral signals of…
Recent observations of several planet-hosting M dwarfs show that most have FUV/NUV flux ratios 1000 times greater than that of the Sun. Here we show that the atmospheric oxygen contents (O2 and O3) of potentially habitable planets in this…
Some atmospheric gases have been proposed as counter indicators to the presence of life on an exoplanet if remotely detectable at sufficient abundance (i.e., antibiosignatures), informing the search for biosignatures and potentially…
Ocean-atmosphere chemistry on Earth has undergone dramatic evolutionary changes through its long history, with potentially significant ramifications for the emergence and long-term stability of atmospheric biosignatures. Though a great deal…
Warm rocky exoplanets within the habitable zone of Sun-like stars are favoured targets for current and future missions. Theory indicates these planets could be wet at formation and remain habitable long enough for life to develop. In this…
(Abridged) Super Earth exoplanets are being discovered with increasing frequency and some will be able to retain stable H2-dominated atmospheres. We study biosignature gases on exoplanets with thin H2 atmospheres and habitable surface…