Swansong Biospheres II: The final signs of life on terrestrial planets near the end of their habitable lifetimes

Abstract

The biosignatures of life on Earth do not remain static, but change considerably over the planet's habitable lifetime. Earth's future biosphere, much like that of the early Earth, will consist of predominantly unicellular microorganisms due to the increased hostility of environmental conditions caused by the Sun as it enters the late stage of its main sequence evolution. Building on previous work, the productivity of the biosphere is evaluated during different stages of biosphere decline between 1 Gyr and 2.8 Gyr from present. A simple atmosphere-biosphere interaction model is used to estimate the atmospheric biomarker gas abundances at each stage and to assess the likelihood of remotely detecting the presence of life in low-productivity, microbial biospheres, putting an upper limit on the lifetime of Earth's remotely detectable biosignatures. Other potential biosignatures such as leaf reflectance and cloud cover are discussed.

Accepted for publication in International Journal of Astrobiology

References in corpus (6)

• The James Webb Space Telescope
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• Atmospheric Retrieval for Super-Earths: Uniquely Constraining the Atmospheric Composition with Transmission Spectroscopy
• Habitat of early life: Solar X-ray and UV radiation at Earth's surface 4-3.5 billion years ago
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• Colors of extreme exo-Earth environments

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• The Vegetation Red Edge Biosignature Through Time on Earth and Exoplanets
• Long Term Planetary Habitability and the Carbonate-Silicate Cycle
• In Search of Future Earths: Assessing the possibility of finding Earth analogues in the later stages of their habitable lifetimes
• From climate models to planetary habitability: temperature constraints for complex life
• Quantifying the Influence of Jupiter on the Earth's Orbital Cycles
• Past, Present and Future Stars that can see Earth as a Transiting Exoplanet
• Searching for Biosignatures in Exoplanetary Impact Ejecta
• The Effect of Seafloor Weathering on Planetary Habitability
• Characteristics of aquatic biospheres on temperate planets around Sun-like stars and M-dwarfs
• The Detectability of Earth's Biosignatures Across Time
• A novel metric for assessing climatological surface habitability
• Maximum Lifetime of the Vegetative Biosphere