The Dry Valley Lakes, Antarctica: From sulfur stains on Earth to sulfur stains in the Jovian system

Most organisms dwell in what we consider to be "normal" environments, while others, which are called extremophiles, may thrive in harsher conditions. These living organisms are mainly of unicellular (both prokaryotes and, to a lesser extent, there are some eukaryotes) But the extremophiles also include multicellular organisms, including worms, insects and crustaceans. In the present work we survey specific extremophiles in some detail. Astrobiology is concerned with all of these extremophiles, as they may be models for extant life in similar environments elsewhere in the universe. In the more restricted search for life through exploration of the Solar System, the main focus is on the preparation of suites of experiments that may attempt to discover the habitability of planets and their satellites. In this context we ask ourselves: What biosignatures can facilitate life detection, both unicellular and multicellular, in extreme environments? The environments that are within reach of present and future space missions include the Jupiter satellite Europa. The icecovered lakes of Antarctica's McMurdo Dry Valleys have long been of interest to astrobiology. These environments harbor unique microbial ecosystems that could orient us how to plan our experiments on Europa.