Letters of Intent received in 2016

LoI 2018-1898
GA Symposium: Origins: From the Protosun to the First Steps of Life

Topics

Collapsing cloud cores
-simulations and observations of dense molecular cores and the formation of solar mass stars

Early environment of the pre-solar nebula
- isotopic anomalies in meteorites and the implications for nearby supernovae; physics of the presolar nebula; location in the Milky Way; single versus binary star formation

Formation and evolution of proto-planetary disks
- observations and modeling of jets, disks, and disk substructures

Physical and chemical properties of proto-planetary disks
- chemical composition of the proto-planetary disk; planetesimals and planetary embryos; snow line; complex molecules; temperatures and densities; magnetic fields,

Early planetary atmospheres and surfaces
- origin of the Earth's water; late heavy bombardment period

Early conditions for habitability
- young stellar output, stellar winds and activity; planetary atmospheric erosion; planetary system dynamics and stability

Earth-like planets
- observations, properties

Early life on Earth
- evidence for early life; early conditions on Earth and the transformation of Earth's atmosphere by early life

Rationale

This is a Letter of Intent to organize an IAU Symposium for the General Assembly in Vienna that will bring together the typically separate fields of Interstellar Matter and Local Universe, represented by Division H, and Planetary Systems and Bioastronomy, represented by Division F. The concept involves one of the most important problems facing all of modern science, namely to find direct evidence for the types of physical processes that eventually formed the Sun, Earth and the beginnings of Life on it. While a considerable number of relatively massive exoplanets have been detected, the present focus is on discovering ever smaller bodies orbiting in habitable zones as candidates for life-bearing planets. With this comes the quest for a deeper understanding of the complex mechanisms leading to such environments, many of which are related to the early epochs of star and planet formation, such as the formation of organic molecules in disks and envelopes, the formation of terrestrial planets in stable orbits, transport of water, erosion of primary or secondary atmospheres in the energetic environment of young stars, etc. Conversely, a deep understanding of existing planetary systems provides clues to the processes relevant during star formation, in particular accretion mechanisms, disk formation, evolution and dispersal, and the evolution of the early stellar output.

What critical conditions subsequently lead to the emergence of life on rocky planets is not yet clear. Although the existence of liquid water is the minimum requirement, based on which the habitable zones are estimated currently, other conditions such as chemical composition of the atmosphere and a proper circulation of volatile elements on the planet's surface could be highly relevant as well. Observations of disks and theoretical models indicate that the content of water and other volatiles in the building blocks of planets could critically depend on chemical processes in the protoplanetary disk and dynamics of planet formation. It is evident that the conditions for habitable environments on planets and the emergence of life are rooted in the formation mechanisms of stars, protoplanetary disks and solids. Progress calls for joint studies of all these issues.

Astronomers in Divisions H and F are making real progress on these problems. Modern facilities like the Spitzer and Herschel infrared telescopes and the ALMA and NOEMA mm-wave interferometers have observed dust emission and gas dynamics in the core regions of molecular clouds, where stars like the Sun are forming. Computers now simulate many stages in this process, including supernova feedback that might have contributed to the isotopic anomalies in meteorites. Interferometers at mm-wavelengths have also observed molecules, ices, and dynamical processes inside proto-planetary disks. In the past decades, the theory of planetary system formation has been stimulated and renewed by the observations of exoplanets. There are several thousand extrasolar planets now in catalogues, based on several different methods of detection. Several of these planets are Earth-sized or slightly larger and orbit their parent stars in the Habitable Zone. Progress in our understanding of planet formation is expected in the near future when observations of exoplanet atmospheres will become more prevalent with JWST and TMT. The latest observations with sensitive high-resolution instruments such as ALMA and VLT SPHERE begin to reveal the formation process of planets in protoplanetary disks. New breakthroughs in planetary statistics, properties, and physical origins are expected from the TESS and CHEOPS missions to be launched soon. With upcoming instruments like JWST, VLT SPHERE and ESPRESSO, and the planned NEID on WIYN for 2019, the next several years should vastly improve our knowledge of the frequency of Earth-like planets, in particular those in the Habitable Zone, and the connection between these types of planets and the mechanisms of star and planet formation. The time is thus ripe and the interest is high for a major IAU symposium on this topic.

This will be the first IAU Symposium to bring together all phases of the processes that brought life to our planet. Only with this comprehensive view can we begin to understand the complex interplay between interstellar dynamics and chemistry, the structure and properties of the pre-solar nebula, early Earth, and the beginnings of life as we know it. We expect a large international interest from both the science community and the general public on this diverse and important issue.

We intend to have both Division H and Division F as coordinating Divisions, unless only one is allowed, in which case Division H will take the administrative responsibility for that role.