EXPOSE

EXPOSE is a multi-user facility mounted outside the International Space Station dedicated to astrobiology. EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights and was designed to allow exposure of chemical and biological samples to outer space while recording data during exposure. EXPOSE is a multi-user facility mounted outside the International Space Station dedicated to astrobiology. EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights and was designed to allow exposure of chemical and biological samples to outer space while recording data during exposure. The results will contribute to our understanding of photobiological processes in simulated radiation climates of planets (e.g. early Earth, early and present Mars, and the role of the ozone layer in protecting the biosphere from harmful UV-B radiation), as well as studies of the probabilities and limitations for life to be distributed beyond its planet of origin. EXPOSE data support long-term in situ studies of microbes in artificial meteorites, as well as of microbial communities from special ecological niches. Some EXPOSE experiments investigated to what extent particular terrestrial organisms are able to cope with extraterrestrial environmental conditions. Others tested how organic molecules react when subjected for a prolonged period of time to unfiltered solar light. EXPOSE has several objectives, specific to each experiments, but all linked to the astrobiology domain. Their collective objective is to better understand the nature and evolution of organic matter present in extraterrestrial environments and their potential implications in astrobiology. These experiments mostly study molecules of cometary interest in order to understand the results of the Rosettamission, the chemistry of Titan (Cassini–Huygens mission), or the organic chemistry of the Martian environment (Mars Science Laboratory and ExoMars project). With the experiments onboard of the EXPOSE facilities, various aspects of astrobiology were investigated that could not be sufficiently approached by use of laboratory facilities on ground. The chemical set of experiments is designed to reach a better understanding of the role of interstellar, cometary and planetary chemistry in the origin of life. Comets and meteorites are interpreted as exogenous sources of prebiotic molecules on the early Earth. All data achieved from the astrobiological experiments on both EXPOSE missions will add to the understanding of the origin and evolution of life on Earth and on the possibility of its distribution in space or origin elsewhere. Data obtained from the studies on complex organics of cometary interest will support the interpretation of in-situ data obtained from the Rosetta mission after landing on Comet 67P/Churyumov-Gerasimenko in 2014, and samples analyzed by the Curiosity and ExoMars rovers on Mars. Finally the chemical experiments will contribute to the understanding of the chemical processes on Saturn's moon Titan and possible analogies to the prebiotic chemistry on the early Earth. The biology experiments used the full extraterrestrial spectrum of solar UV radiation and suitable cut-off filters to study both, the role of the ozone layer in protecting our biosphere and the likelihood of resistant terrestrial microorganisms (extremophiles) to survive in outer space. The latter studies will provide experimental data to the lithopanspermia hypothesis, and they will provide basic data to planetary protection issues. To get better insight into the habitability of Mars, one set of samples was exposed to simulated Martian conditions (UV-radiation climate, pressure, atmosphere), with and without a protective cover of simulated Martian soil. The biological test samples selected are hardy representatives of various branches of life. There were three EXPOSE experiments completed between 2008 and 2015: EXPOSE-E, EXPOSE-R and EXPOSE-R2. The EXPOSE-E was launched on February 7, 2008 on board the Space Shuttle Atlantis and was mounted on the ISS European module Columbus to the European Technology Exposure Facility (EuTEF). EXPOSE-R was launched to the ISS on November 26, 2008 from Baikonur in Kazakhstan on board of a Progress capsule and was mounted on the ISS Russian module Zevzda. EXPOSE-R2 was launched EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated Martian surface conditions (tray 2). The different experiments consisted in exposing solid molecules, gas mixtures or biological samples to the solar ultraviolet (UV) radiation, cosmic rays, vacuum and temperature fluctuations of outer space as the ISS repeatedly passed between areas of direct sunlight and the cold darkness of Earth's shadow. At the end of the exposition period, EXPOSE-E was brought back to the ground in September 2009 as part of the Space Shuttle Discovery mission STS-128. EXPOSE-R was brought back in 2011 by a Soyuz spacecraft. From the landing site in Kazakhstan, the trays were returned via Moscow and distributed to scientists for further analysis in their laboratories.