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Photosynthesis in hydrogen-dominated atmospheres
William Bains1, Sara Seager2, Andras Zsom3
1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA. bains@mit.edu.
Life (Basel, Switzerland)
|November 21, 2014
Summary
Photosynthesis may occur on rocky planets with hydrogen-rich atmospheres, utilizing methane. This could produce ammonia as a biosignature, suggesting complex life may evolve in such alien environments.
Area of Science:
- Astrobiology
- Planetary Science
- Exoplanet Research
Background:
- Exoplanet discoveries reveal diverse environments beyond Earth.
- Super-Earths with stable, hydrogen-dominated atmospheres are increasingly found.
- Life detection strategies should consider non-Earth-like conditions.
Purpose of the Study:
- Investigate the potential for photosynthesis on rocky planets with hydrogen-rich atmospheres.
- Explore methane-based photosynthesis as an alternative to carbon dioxide-based photosynthesis.
- Identify potential biosignature gases for life in hydrogen-dominated exoplanet atmospheres.
Main Methods:
- Chemical pathway analysis for methane-based photosynthesis.
- Comparison of energy requirements for methane versus carbon dioxide photosynthesis.
- Assessment of potential biosignature gas production and detectability.
Main Results:
- Methane-based photosynthesis is energetically feasible with lower energy photons compared to CO2-based photosynthesis.
- Hydrogen (H2) is a likely byproduct but difficult to distinguish from atmospheric H2.
- Ammonia (NH3) is a potential, uniquely identifiable biosignature gas.
Conclusions:
- Methane-based photosynthesis is a plausible metabolic pathway for extraterrestrial life.
- Ammonia could serve as a key biosignature for life on hydrogen-rich exoplanets.
- Such environments may support the evolution of complex life.
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