FM 9: Highlights in the Exploration of Small Worlds

Small bodies of the Solar System are believed to be the remnants - either fragments or “survivors”- of the swarm of planetesimals from which the planets were formed. They are thus primitive leftover building blocks of the Solar System formation process that can offer clues to the chemical mixture from which the planets formed some 4.6 billion years ago. By investigating in detail the physical and chemical properties of asteroids, comets, trans-neptunian objects and dwarf planets, one can characterize the conditions and processes of the Solar System's earliest epoch. This extends naturally also to some planetary satellites, which share, with small bodies and dwarf planets, similar properties and/or formation history.

2014-2015 are the golden years of the space exploration of these Solar System objects. It will be the right time to gather a large community in astronomy, space science, planetary science, and cosmo-chemistry, and to present space missions that either have just finished their harvest, or are in the middle of an effervescent period of new results, not mentioning the next generation of space missions under development.

• The ESA Rosetta mission will reach comet 67P/Churyumov-Gerasimenko in mid-2014, deposit the lander Philae in November 2014, and remain in the close vicinity of the comet until the end of 2015. Not less than 20 instruments will study in depth one of the most primitive objects of the Solar System.
• After its successful journey around asteroid Vesta in 2011, the Dawn mission of the NASA Discovery Program will rendezvous with dwarf planet (1) Ceres in Spring 2015.
• The Cassini spacecraft will keep exploring the Saturn system, and will perform three additional close flybys of Enceladus in 2015, offering opportunity to better understand its surprising activity.
• In July 2015, the News Horizons NASA mission will flyby and study dwarf planet Pluto and its moons.
• In addition, whereas the NEOWISE has been revived with the goal of discovering and characterizing quantities of near-Earth objects, the ESA Gaia mission will undertake in 2014-2018 a comprehensive spectroscopic investigation of hundreds of thousands of asteroids and comets.
• Last but not least, significant progress in the characterization of small Solar System bodies, dwarf planets, icy and irregular planetary satellites is expected from Earth-based large surveys (e.g. Pan-STARRS), observations with large observing facilities (e.g., ALMA, Herschel, HST, and 10-m class optical telescopes), as well as from geochemical analysis of meteorites, micrometeorites, and interplanetary dust particles.

The goal of the proposed focus meeting is to highlight results obtained from the Rosetta, Dawn, New Horizons, Cassini-Huygens, and Gaia missions, as well as recent achievements obtained from other space facilities, including past space missions, ground-based telescopes, and geochemical analyses. With, in particular, the discovery of Main-Belt comets and the analysis of comet samples collected by the Stardust mission, it has become increasingly evident that the differences between Main-Belt primitive asteroids and comets, are much less sharp than previously thought. Major progress in our understanding of the asteroid-comet continuum is expected in the coming years, both from physical, chemical and dynamical analyses, as well as models of the chaotic early Solar System. This topic will be a focus of the meeting. Rosetta will provide unprecedented information on the chemical and isotopic properties of the primitive material trapped in cometary nuclei. In parallel, ALMA will unravel the chemistry of protoplanetary disks and star-forming regions, finally allowing a quantitative comparison with the Solar System composition. This meeting will thus be the right time to synthesize analogies and differences between star-forming regions and Solar Nebula material, and better understand our astrochemical history.

New Horizons and Dawn will explore for the first time the poorly known Pluto-Charon system and Ceres respectively, thus completing the spectra of characterized icy bodies from the Main Asteroid Belt to the Kuiper Belt. The Cassini-Huygens mission around Saturn has already revealed a wide variety of icy objects, with different surface and interior characteristics, though originating from a very specific region in the Solar System. Comparative studies between the dwarf planets and the icy moons of the giant planets will permit us to better understand why bodies that formed from rather similar building blocks follow so different evolutionary paths and how their local environment affected their long-term evolution. The meeting, just after Pluto-Charon’s flybys by New Horizons, a few months after Dawn’s arrival at Ceres, and toward the end of the Cassini-Huygens mission, will be the first opportunity to discuss the latest results gathered by these space missions and to start understanding the complex and rich evolution of the diverse icy bodies of the Solar system.

In summary, the IAU General Assembly in 2015 is a tremendous opportunity to highlight and spread to a large audience the spectacular results of several space missions towards small bodies, icy satellites, and dwarf planets of the Solar System. It is also a tremendous opportunity to address recent progresses made on their physical and chemical properties, their interrelations and their evolutionary paths, by combining observational, experimental, and theoretical approaches. The study of planetary formation is an interdisciplinary topic, per nature. The proposed focus meeting will gather researchers of different communities and young colleagues for a better understanding of the Solar System formation and evolution.

Our proposed focus meeting presents synergies and unique differences with the proposed IAU GA symposium "Asteroids: New Observations, New models" submitted by Steven Chesley. Indeed, this symposium focuses on asteroids, including main-belt comets, for which spacecraft observations are only a modest part, while our proposal emphasizes on space missions, and covers the full spectrum of small bodies, including comets, icy satellites and primitive meteorites. Moreover, the asteroid symposium will emphasize on dynamical processes and the dynamical and physical structure of asteroids, with limited emphasis on the chemistry and composition of these bodies. This is in contrast to our proposal that emphasizes cosmo-chemistry and physical properties across the continuum of small bodies, with the objective to better understand their interrelations in the context of Solar System formation. These two meetings are thus fully complementary to each other, and the organizing committees will make sure to keep this complementarity when finalizing their meeting programs.

We are aware of the proposed Focus Meeting "Search for water and life's building blocks in the universe" submitted by S. Kwok, P. Ehreunfreund, and E. Bergin. There will be some slight but complementary overlap in some of the topics between these two FMs that will serve as an excellent means of tying the topics of these two FMs together and providing a smooth transition between GA attendees that wish to attend both. The proposed FM on Water provides a broad and cutting edge overview of the topic from the ISM to life, whereas the FM on small bodies gives a detailed look at current missions related to small bodies that will be of interest to the whole GA. By having both FM we capture the global view and connections to many disciplines along with some fascinating details of interdisciplinary interest.

The Focus meeting will be advertised on several sites and mailing-lists, in addition to IAU, at national levels from SOC members (USA, Europe, South America, Japan) and through space agencies.

The question of the formation of the Solar System has always sparked enthusiasm to the general public. The spectacular images taken by the space missions will be a wonderful means to pick the interest of the public, especially the schoolchildren. The SOC will propose a panel of speakers to visit schools, in the framework of Education & Public Outreach actions planned by the astrobiology group of the University of Hawaii at the time of IAU GA. We will seek for the support of national and international space agencies to provide materials for the schools, such as movies, posters, exhibitions, games, model spacecrafts, etc...