More than 5000 Exoplanets have been detected, with another >5000 candidates awaiting confirmation. Among these is a growing number of planets of approximately Earth size and mass. A significant number of them orbit their host stars in the habitable zone and potentially harbor extraterrestrial life. While the concept of the habitable zone is useful for a first assessment of the chance of detecting extraterrestrial life, it is likely too unspecific for targeting sophisticated and costly follow-up observation. Considerations of more specific planetary physical properties include the balance between land and (deep) ocean surfaces, the availability of water vs nutrients from riverine sources such as phosphorus and nitrogen and the potential for the built-up of free oxygen to support more advanced life forms.
A discussion of the “workings” of exoplanets should thus go far beyond simple models of their interior and their environment based on their radius and mass and on their orbital distance from the host star. Rather, the discussion should include many more aspects of the geosciences such as the tectonic modes (viz. plate vs single plate tectonics), interior, atmosphere and magnetic field evolution and star – planet interactions, from the process of formation to later in the evolution of the planet. Since many host stars are low mass stars, tidal interactions will be worth considering. The rocky planets in the solar system provide type-examples of lifeless and mostly waterless worlds that may have earlier had more clement environmental conditions. In addition, these planets complement terrestrial data with viable observational evidence.
Rocky Exoplanets are important for the geoscientist as objects of comparison, if only to assess how unusual or common Earth is and motivate considerations of Earth’s properties in ways that would likely never have been raised without the comparison.
The workshop will cover a wide range of topics, bringing exoplanet observers and modelers, astrophysicists, planetary scientists, astrobiologists and Earth scientist together to learn about Earth-sized rocky planets in general and discuss the chances of finding extraterrestrial life and strategies of how to best detect it. It will be the first workshop of its kind for ISSI. It is timely considering the wealth of data already available and to be expected from JWST and coming missions like PLATO and ARIEL. The workshop fits well with other activities at ISSI including several international teams concerned with exoplanet observation and recent working groups on biosignatures and life in the Martian underground.
The Workshop and the resulting publications will cover the following main themes:
- Interior structure, modeling and relevance for planetary evolution
- Interior dynamics, tectonic modes and planetary evolution
- Habitability, origin and evolution of life and observable biosignatures
- Formation and evolution of atmospheres and hydrospheres
- Star/Planet interactions, magnetospheres and upper atmospheres
- Future observations
Based on the presentations and discussions during the workshop, we will select about 15 sub-topics to be published as (review) papers in a topical collection of Space Science Reviews and as a printed volume in the Space Science Series of ISSI by Springer Nature.
Header Image: Foreground: Courtesy of Lena Noack, FU Berlin. Background: Except from the Hubble Ultra Deep Field view (credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team)