Key science questions
Sagan et al. (1993) analyzed a spectrum of the Earth taken by the Galileo probe, searching for signatures of life and concluded that the large amount of O2 and the simultaneous presence of CH4 traces are strongly suggestive of biology. To characterize a planet’s atmosphere and its potential habitability, we look for absorption features in the emergent and transmission spectrum of the planet. The spectrum of the planet can contain signatures of atmospheric species, what creates its spectral fingerprint. On Earth, some atmospheric species exhibiting noticeable spectral features in the planet’s spectrum result directly or indirectly from biological activity: the main ones are O2, O3, CH4, and N2O. CO2 and H2O are in addition important as greenhouse gases in a planet’s atmosphere and potential sources for high O2 concentration from photosynthesis. The presence or absence of these spectral features (detected individually or collectively) will indicate similarities or differences with the atmospheres of terrestrial planets, and its astrobiological
The KEY questions:
- What could constitute a (remotely detectable) biosignature under what conditions?
- Conditions under which other biosignatures can form
- e.g. methane biosignature and the limits of methanogens.?
- Minimum physical & chemical requirements to create a habitable environment
- Early environments impact on evolution of life
- Extreme physical & chemical limits for life in general
- Physical and chemical limits of photosynthesis
- Impact of total atmospheric pressure on microbes
- Man-made biosignatures & identification of advanced life
- SuperEarth environments and life
- Influence of stellar activity on an atmosphere
- Is there a min or maximum mass for habitability?
- Is there a minimum mass for plate tectonics on a planet?
- What geochemical cycles could globally dominate a planet?
Saturday 5 September 2009 by Vincent Coudé du Foresto