From Saturday 17 September, astronauts from ESA, NASA, JAXA and ROSCOSMOS were living and working in the dark and humid underground environment for five days on their CAVES ‘mission’ a unique underground space experience organized by ESA. During the ‘mission’ different samples were taken and DLR, especially the Department for Radiation Biology (Institute of Aerospace Medicine) is participating this project by analyzing the taken samples in terms of microbiology.