Videoconference by Frances Westall, geologist, astrobiologist, director of the exobiology group of the Centre for Molecular Biology of Orléans, president of the European Association of Astrobiology.

Has life appeared on Earth only, or is it a “cosmic phenomenon”, as thinks the Nobel laureate, Christian de Duve ? Can it appear everywhere or are there certain constraints? Indeed, while the ingredients of life – organic molecules, water, energy – are generally available, the geological context must still be relevant, i.e. a rocky planet with hydrothermal activity in a context Volcanic. Such conditions for the emergence of ex novo life existed on several planets in the young Solar System (Earth, Mars, perhaps Venus and even now icy satellites, such as Europe or Enceladus), but are no longer present, even on the Earth. However, the high number of suitable planets in the Universe suggests that life may be widespread, in a rather primitive form, such as anoxygenic microorganisms, the problem being rather how to identify them on an exoplanet.