What is a habitable environment? - answers from abservations of a global transect

Extremophiles are specialists which colonise special niches in these extreme environments due to there adaptation capacities attained during the evolution of life. Some examples of extremophiles and their potential to deal with harsh conditions as well as the characterisation of their niches will be presented. Based on observations and results obtained in the 10th German Antarctic North Victoria Land Expedition (GANOVEX X) in the area of the Transantarctic Mountains led by the German Geosciences and Resource Research Society(BGR) and during an environment characterisation campaign of the European Alps and the Spanish Mountains\Sierra de Gredos" supported by the German Ministry of Economy and Technology (BMWi) a global transect from temperate Alpine regions to Mediterranean mountains and Polar Mountain regions can be analysed. Due to a summary of these results we are able to compare different strategies of colonisation in different habitats of the global mountain transect by cosmopolitan and endemic species as there are, the colonisation of rocks, fissures, cracks, polygon forming substrates, permafrost and glaciers. Data of UV B-, PAR- and IR-radiation measurements, humidity and temperature as well as the activity of microorganisms are accomplishing with more details the habitat characterisation and may give relevant information on probably niches for life on other planets as e.g. the planet Mars and may give answers on the question what is a habitable environment. These results will also form the basis of a series of new space experiments on satellites or on the International Space Station (ISS) and furthermore may lead to progress in probes- and rover-development for particular \hardly" accessible terrains.