Jean-Pierre Paul de Vera, Mashal Alawi, Theresa Backhaus, Mickael Baque, Daniela Billi, Ute Boettger, Thomas Berger, Maria Bohmeier, Charles Cockell, Rene Demets, Rosa de la Torre Noetzel, Howell Edwards, Andreas Elsaesser, Claudia Fagliarone, Annelie Fiedler, Bernard Foing, Frederic Foucher, Jörg Fritz, Franziska Hanke, Thomas Herzog, Gerda Horneck, Heinz-Wilhelm Hübers, Björn Huwe, Jasmin Radha Joshi, Natalia Kozyrovska, Martha Kruchten, Peter Lasch, Natuschka Lee, Stefan Leuko, Thomas Leya, Andreas Lorek, Jesus Martinez-Frias, Joachim Meessen, Sophie Moritz, Ralf Moeller, Karen Olsson-Francis, Silvano Onofri, Sieglinde Ott, Claudia Pacelli, Olga Podolich, Elke Rabbow, Günther Reitz, Petra Rettberg, Oleg Reva, Lynn Rothschild, Leo Garcia Sancho, Dirk Schulze-Makuch, Laura Selbmann, Paloma Serrano, Ulrich Szewzyk, Cyprien Verseux, Jennifer Wadsworth, Dirk Wagner, Frances Westall, David Wolter, Laura Zucconi

• BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports-among others-the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs andBIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports-among others-the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.…