In this 9th session of the internet-based live lectures between Universities and Institutes, Dr Michel Viso of CNES discusses planetary protection. Planetary protection is based on the article IX of the Outer space treaty from the United Nations, in force since 1967. The Committee for Space research (COSPAR), an international science organisation edictally authorized to recommend how to handle space missions aiming at the various bodies of the Solar System. The recommendations are regularly updated as new knowledge is gained about planets, satellites and the terrestrial microbes. The ultimate responsibility of the implementation of those recommendations is the charge of space agencies and governments.