A ground-based program for exobiological experiments on the International Space Station

The International Space Station will carry the external facility EXPOSE for exobiological studies under free space conditions and/or selected space pa rameters. Complementary to such experimentation in space, a profound ground support program under simulated space conditions is required: (i) to suppo rt the scientific EXPOSE community in the definition of the experiments und er simulated space conditions; (ii) to determine the compatibility of the d ifferent experiments (e.g., organics and biology); (iii) to optimize the ex periments; (iv) to perform experiments sequence tests under simulated EXPOS E environment conditions; (v) to run ground controls in parallel to the mis sion; and (vi) for postflight analysis of phenomena observed in space. For these laboratory studies, testbeds are available at DLR and GSF that simula te the parameters of space, such as vacuum, solar electromagnetic and cosmi c ionizing radiation, temperature extremes and reduced gravity that can be applied separately, or in selected combinations. Such studies contribute to answer several questions pertinent to exobiology, such as the relevance of the delivery of extraterrestrial organic molecules to the Earth for the or igin of life, the role of solar UV radiation in genetic stability, strategi es of adaptation to environmental extremes, the probability and limits for interplanetary transfer of life, and the needs for planetary protection. (C ) 2000 Elsevier Science Ltd. All rights reserved.