What HabEx and LUVOIR can tell us about Habitability, Inhabitation, and Biosigning
Abstract
In the astrobiological community, a planet is defined as habitable if it has subaerial (exposed to the atmosphere) liquid water on its surface. The key assumption associated with this definition is that subaerial liquid water is essential for life. A planet is defined as inhabited if it actually has life present on it, and we will define a planet as "biosigned" if we can measure biosignatures in its atmosphere that provide a strong indication that it is inhabited. Barring clear signs of intelligence, it is unlikely that we will be able to definitively establish whether a planet is inhabited in the next 50 years, but we may be able to establish whether biosigning is common and whether our conception of habitability is useful. In this presentation we will discuss what NASA's space telescope mission concepts HabEx and LUVOIR might reveal about these issues. For example, suppose we find 100 habitable planets and all are biosigned. This would indicate that habitability is a useful concept, and that life is probably common in the universe (although we would be limited in our confidence in this statement by uncertainty in whether biosigned planets truly are inhabited). Alternatively, suppose we find 100 habitable planets and none are biosigned. This would indicate that habitability may not have much to do with life, and that life that we can detect with biosignatures is rare in the universe. But how many planets would we need in order for conclusions like these to be robust? Is 10 enough? Would even 1 planet be enough if we were certain that we would detect a biosignature on it if it existed? In this presentation we will address these questions by developing a Bayesian framework to combine current knowledge and uncertainty about the origin of life and the frequency of potentially habitable planets with the observational capabilities of HabEx and LUVOIR. We will determine the likelihood that different variants of both missions will be able to constrain the usefulness of the habitability concept, what the price point for scientific payoff is, and which mission makes the most sense to choose from the standpoint of maximizing what we learn about habitability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.P52A..05A
- Keywords:
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- 5215 Origin of life;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5494 Instruments and techniques;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS