Putting astronauts in suspended animation--halting their metabolisms at temperatures below freezing--would theoretically preserve them indefinitely, but this technique presents its own set of problems. Namely, ice. "Everything in biology is soft and squishy," says Gregory Fahy, vice president and chief scientific officer at the cryobiology research firm 21st Century Medicine. "If ice forms in a living system, it can rip up intracellular structures and make blood vessels leak." Problematic for our interstellar explorers, to say the least. To forestall the freezing process in organs for transplant, Fahy and his colleagues have tried diluting water-based bodily fluids with agents like glycerol, a process analogous to putting antifreeze in a car's radiator. Yet cells need water, so Fahy's strategy--so far unsuccessful--depends on fooling thirsty cells into thinking they have plenty of H2O, when in reality they're filled with biological antifreeze. Astronauts would be wise to approach this strategy with caution.