Letters of Intent for 2015

LoI 2015-204
Focus Meeting: Signs of Life: Exoplanets and the Search for Biomarkers

Date: 4 August 2015 to 4 August 2015
Location: to be held during the next General Assembly of the IAU, in Honolulu, HI USA Aug. 3-14, United States
Contact: Rachel Osten (osten@stsci.edu)
Coordinating division: Division F Planetary Systems and Bioastronomy
Chair of SOC: Rachel Osten (STScI)
Chair of LOC: ()



What kinds of planets are most suited for studies of habitability?
What observations will be necessary to demonstrate habitability?
What are the biomarkers that will tell us we’ve seen the signature of life on an exoplanet?



From the Copernican Revolution to the present day, humankind has been continually engaged in a debate about our place in the universe. The discovery of extrasolar planets and the possibility of life outside our solar system extends this discussion. There are several steps on the road to answering the question “Are we alone?”. The increase in the number of exoplanets detected in recent years provides the ground-work for future explorations of their habitability. A scrutiny of this census of exoplanets can reveal which harbor conditions necessary to support life. However, the sample size of confirmed habitable planets is the smallest it could be, and there is a fantastic diversity to the conditions where life can be sustained within that one example. This motivates a focussed discussion of the strategy that should be used by astronomers to identify and characterize the likely planets to harbor life. It also spurs a vigorous discussion about what markers should be used as those signatures and how they should be interpreted.

Emerging discoveries in the field of planetary systems reveal a diversity of exoplanet properties which stretches present understanding of planet formation. Determining which exoplanets are potentially habitable starts with an understanding of the gross planetary properties. The existence of potential biosignatures is necessary but not sufficient to establish habitability; the interpretation depends also on the specific conditions about the atmosphere which they reveal. These factors require an interplay between astronomers focussed on each step, in order that gaps in understanding can be addressed.

The proposed focus meeting will be one day in length. The date given is notional, and any day within the two week-long General Assembly is sufficient.

The topics listed above are timely, as recent developments have shown progress in addressing them. Advances in observing exoplanet atmospheres are occurring in concert with a deepening understanding of the dynamic physical and chemical makeup of these atmospheres. They also illustrate the complementarity inherent in science done at different wavelengths. The general assembly is an excellent venue for bringing together these diverse communities.

The timing of the General Assembly in 2015 fits well with progress being made on several fronts. First results of GAIA will constrain distances to exoplanet hosts and provide some astrometric constraints on exoplanet orbits, and the first intermediate data products will be released around the time of the IAU general assembly in 2015. The astrometric precision of the ALMA telescope will also provide constraints on exoplanets. Building on the legacy of Kepler, the Wide Field Infrared Survey Telescope (WFIRST) and the Transiting Exoplanet Satellite (TESS) will complete our knowledge of exoplanet demographics. WFIRST, through its microlensing technique, will search for planets orbiting stars at larger radii than Kepler and TESS will find super-Earths around low mass dwarfs that are very close to the Sun.
Ground-based extremely large telescope projects such as TMT, GMT, and E-ELT are aiming to study the atmospheres of young, massive exoplanets. The James Webb Space Telescope will launch us into an era of exoplanet characterization, and has the power to detect molecular features from H2O and CO2 in super Earths around nearby stars. Advances in modeling exoplanet atmospheres and the interpretation of spectra will need to be folded into the discussion. This meeting includes participation from scientists associated with the aforementioned missions.

The 2015 IAU General Assembly offers the opportunity to reflect on progress towards answering questions laid down at the beginning of the decade. The General Assembly offers a venue for astronomers from different countries and scientific communities to come together, and so is appropriate for the meeting being proposed. In addition to the attendees to the General Assembly, we would also like to broaden participation through web interaction with astronomers at other institutions.