Detectability Simulations of a NIR Surface Biosignature on Proxima Centauri b with Future Space Observatories

Abstract

Telescope missions are currently being designed which will make direct imaging of habitable exoplanets possible in the near future, and studies are needed to quantify the detectability of biosignature features in the planet's reflectance spectrum. We simulated the detectability of a NIR-absorbing surface biosignature feature with simulated observations of the nearby exoplanet Proxima Centauri b. We modeled a biosignature spectral feature with a reflectance spectrum based on an anoxygenic photosynthetic bacterial species that has strong absorption at 1 um, which could make it well suited for life on an M-dwarf hosted planet. We modeled the distribution of this organism across the planet's surface based on climate states from a 3D General Circulation Model (GCM), which were Archean and Proterozoic-like exo-Earth analogues. We included the GCM runs' prognostically simulated water clouds and added organic haze into the Archean-like atmospheres. We simulated observations of these Proxima Centauri b scenarios with the LUVOIR-A and B telescope concepts, with LUVOIR-B serving as a proxy to the planned Habitable Worlds Observatory (HWO). We calculated integration times necessary to detect the biosignature, and found that it would be detectable on Proxima Centauri b if the organism is moderately abundant (greater than a 1-4% global surface area coverage), as long as the atmosphere is transmitting in the wavelength range under consideration. Small amounts of methane, clouds, and haze do not greatly impede detectability. We found preliminary evidence that such a biosignature would be detectable on exoplanets within 15 pc, but further investigations are needed to corroborate this.

31 pages, 9 figures, 2 tables

References in corpus (12)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• Vegetation's Red Edge: A Possible Spectroscopic Biosignature of Extraterrestrial Plants
• The Pale Orange Dot: The Spectrum and Habitability of Hazy Archean Earth
• Spectral signatures of photosynthesis II: coevolution with other stars and the atmosphere on extrasolar worlds
• The habitability of Proxima Centauri b II. Possible climates and Observability
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present
• Vegetation signature in the observed globally-integrated spectrum of Earth: Modeling the red edge strength using simultaneous cloud data and application for extrasolar planets
• Nonphotosynthetic Pigments as Potential Biosignatures
• No Conclusive Evidence for Transits of Proxima b in MOST photometry
• Probing the capability of future direct imaging missions to spectrally constrain the frequency of Earth-like planets
• Detectability of Surface Biosignatures for Directly-Imaged Rocky Exoplanets
• Purple is the new green: biopigments and spectra of Earth-like purple worlds