Astrobiologie : état actuel et prochaines étapes
Colloque organisé par André Brack du 10 au 15 avril 2007
Développements récents en astrobiologie et réflexions sur la coopération internationale et sur certains aspects sociétaux liés à l’astrobiologie.
André Brack, Jan Bredehöft, Hervé Cottin, Luis Delaye, Pascale Ehrenfreund, David Field, Rose Grymes, Gerda Horneck, Helmut Lammer, Doron Lancet, Antonio Lazcano, Anatoliy Pavlov, Györgyi Ronto, Ewa Szuszkiewicz, Malcom Walter.
Le séminaire « Astrobiologie » a réuni 15 astrobiologistes européens et internationaux venus d’Allemagne, d’Australie, d’Autriche, du Danemark, des Etats-Unis, de France, de Hongrie, d’Israël, du Mexique, des Pays-Bas, de Pologne et de Russie.
Les travaux ont consisté à :
- faire le point sur les avancées en astrobiologie
- renforcer les coopérations internationales
- mener une réflexion approfondie sur les aspects sociétaux liés à l’astrobiologie.
L’astrobiologie a pour objet l’étude de la vie dans l’Univers. Actuellement, les recherches se limitent essentiellement à la chimie du carbone dans l’eau, principaux acteurs de l’émergence de la vie terrestre, il y a quelques quatre milliards d’années.
C’est vers ce carrefour de la chimie du carbone dans l’eau que convergèrent les conférences présentées pendant le séminaire, allant de l’astrophysique aux sciences de la vie : chimie interstellaire, chimie cométaire, formation et évolution des planètes, chimie de l’origine de la vie, photochimie, microfossiles bactériens, dernier ancêtre commun, recherche de vie dans le Système Solaire et planètes extrasolaires.
Les discussions portèrent également sur le renforcement des coopérations internationales ainsi que sur les aspects sociétaux liés à l’astrobiologie : vulgarisation, enseignement, médias et éthique.
Au final, les participants se sont engagés à :
- renforcer la coopération internationale
- mieux harmoniser les trop nombreux colloques internationaux en astrobiologie
- sensibiliser davantage les jeunes scientifiques à ce domaine multidisciplinaire de recherche en évolution permanente
- mieux expliquer l’astrobiologie à tous les publics
The international meeting « Astrobiology » gathered 15 astrobiologists from Australia, Austria, Denmark, France, Germany, Hungary, Israël, Mexico, Netherlands, Poland, Russia and United States. There were two objectives of the meeting: to overview the recent developments in astrobiology and to have in depth reflections on international cooperation and on some societal aspects related to astrobiology.
The ultimate goal of astrobiology is the search for life in the Universe. Today, the efforts are dedicated to the chemistry of carbon in water, the key ingredients for the emergence of terrestrial life, about 4 billion years ago. All the presentations given at the meeting dealt with this chemistry, at the intersection of different sciences going from astrophysics to life sciences: interstellar chemistry, chemistry of cometary, formation and evolution of planets, chemistry of the origin of life, photochemistry, primitive microfossils, last common ancestor, search for life in the solar system, exoplanets.
Ewa Szuszkiewicz (Szczecin, Poland) presented the most basic context for life, i.e. star and planet formation and evolution. Infrared and optical observations of the star forming regions combined with computer modelling are helping us to understand the different stages, starting from the molecular cloud collapse, through a deeply embedded protostellar phase, a circumstellar disc and collimated outflow, a protoplanetary disc in which planetesimals and protoplanets form via sedimentation and agglomeration till a mature planetary system in orbit around the star. Pascale Ehrenfreund (Leiden, The Netherlands) compiled the current knowledge on interstellar carbonaceous chemistry. This chemistry seems to follow common pathways throughout space and time since carbonaceous molecules in the gas or solid state, refractory or icy, are observed in similar abundances and composition in galaxies, nearby or distant. The largest fraction of carbon in the universe is incorporated into aromatic molecules such as gaseous polycyclic aromatic hydrocarbons as well as solid aromatic structures. David Field (Aarhus, Denmark) described the interstellar synthesis and the delivery, in meteorites and micrometeorites, of organic molecules needed to start life. He considered the question of how such chemicals came to be present in these primitive bodies dating from the birth of the solar system and the question of whether these complex prebiotic organics were made in dark molecular clouds, where stars form, or whether they stem from a later period associated with processing in the solar nebula itself. Hervé Cottin (Créteil, France) described observations, modelling and experimentation of cometary chemistry, in the laboratory and in Earth orbit. Having never been differentiated and being located far away from the Sun, comets probably host pristine matter reflecting the physical-chemical conditions prevailing at the very beginning of the planetary system and even in the protosolar nebulae. Many organic molecules have already been detected in comets, some of which present a potential prebiotic interest. Comets are the archives of space and chemistry is the Rosetta’s stone allowing us to decipher their message. André Brack (Orléans, France) presented the chemistry of the origin of life which emerged on Earth in water about 4 ± 0, 2 billion years with a set of organic molecules able to self-reproduce and also able to evolve. Organic matter might have been formed in the primitive Earth’s atmosphere and/or near submarine hydrothermal systems but a large fraction of organic molecules was delivered by meteorites and micrometeorites. Doron Lancet (Rehovot, Israel) proposed a computational simulation of the prebiotic evolution of vesicles, a lipid world having preceded the cellular world. Jan Bredehöft (Bremen, Germany) underlined the importance of symmetry breaking in astrobiology and reviewed the inventory of the many theories on the origin of biological homochirality, driven either by chance or by a determinate physical force.
The second part of the conference was dedicated to terrestrial life as a reference. Malcolm Walter (Sydney, Australia) described the 3.4-3.5 Ga years old traces of early life found in the Barberton Mountain land of South Africa and the Pilbara region of Western Australia. Györgyi Rontó (Budapest, Hungary) presented the role of UV on biological systems, especially the UV damage of nucleic acids, as learned from experiments in the laboratory and in space. Antonio Lazcano (Mexico City, Mexico) explained that the accumulation of free oxygen in the atmosphere is reflected in the size and composition of prokaryotic genomes, and in the presence of manifold mechanisms of protection against oxidation damage. Luis Delay (Mexico City, Mexico) presented several reconstructions of the gene sequence of the last common ancestor (LCA), performed by using the information derived from hundreds of completely sequenced genomes. According to the different methods used, the set of universally conserved genes inherited from the LCA ranges from a highly conserved core of 63 genes to approximately 700 genes. Anatoliy Pavlov (Saint Petersburg, Russia) described the thermophilic microbial community sampled in frozen volcanic deposits of Kluchevskaya volcano group collected during an expedition to Kamchatka as a model of a Martian ecosystem.
The third part of the conference focused on the search for extraterrestrial life. Helmut Lammer (Graz, Austria) discussed the habitability of Earth-like planets and exoplanets. By studying the contribution of the solar/stellar radiation and particle environment to the atmosphere and hydrosphere, it is possible to evaluate how far it is possible to extrapolate the principles that generated Earth’s long-time habitable environment to other terrestrial solar planets like Venus and Mars and potential terrestrial exoplanets. Early Venus and Mars, subsurface oceans of icy satellites like Europa, Titan, Enceladus, hydrocarbon lakes of Titan, could also have been possible habitats in the young Solar System. Gerda Horneck (Köln, Germany) gave a presentation on human missions to Mars and planetary protection. She stressed that before planning any human exploratory mission, the critical issues that need to be investigated concern human health and the well being, the protection of Mars in its pristine condition, as well as the protection of the Earth and its biosphere from potentially harmful agents brought back on return of the astronauts.
Finally, Rose Grymes (Santa Cruz, USA) presented the state of astrobiology in the US, based on the answers of a survey. A significant majority of respondents agree that astrobiology is a bona fide field, interdisciplinary in its conduct, with identifiably unique perspectives. All participants believed NASA funding was the most critical factor contributing to current maturity of astrobiology. A broad majority says that astrobiology has attracted students to colleges and mentors offering training in this area. The interdisciplinary perspectives acquired by astrobiology students are felt to be advantageous.
Unexpectedly, the meeting accreted Francis Albarède, a geochemist at the Ecole Normale Supérieure de Lyon, in residence at Les Treilles for writings, who gave an impressive presentation of the geology of the primitive Earth.
2) Societal aspects
We had in depth discussions concerning society aspects related to astrobiology and international cooperation. The participants decided to create a website to demonstrate the worldwide dimension of the astrobiology community. Regarding education, the online Astrobiology Course Network initiated by 5 universities (Turku, Dresde, Salzburg, Paris 12, Open University), will be continued and will be enlarged to new universities. It was acknowledged that public outreach must be improved in Europe. It has been decided to build a standard “universal” astrobiology lecture and to consider making a video game, in particular to stress the difference between science and belief, such as creationism and intelligent design. We should also have a more dynamic attitude toward the media, by organising dedicated short meetings for the media, for example. The ethical aspects of astrobiology were also discussed, more precisely those related to space missions. We agreed that scientific exploration must always be preferred to conquest and that the explored land must gain the status of common patrimony of humanity i.e. will belong to everybody and will be managed for the common interest. There is a real need to reinforce the international cooperation within the Federation of Astrobiology Organizations, including the Australian Centre for Astrobiology, the Astrobiology Society of Britain, the Spanish Centro de Astrobiologia, the European Astrobiology Network, the French Groupement de Recherche en Exobiologie, the Israel Society for Astrobiology and the Study of the Origin of Life, the American NASA Astrobiology Institute, the Red Mexicana de Astrobiología and the Swedish Astrobiology Center by organising quarterly teleconferences and releasing a newsletter.