H2O. Water, a cosmic adventure. Water is abundant on Earth, the so-called ocean-covered blue planet. Abundant, but precious, sought after in arid regions and so often coveted. Precious, it is even more so once left our miraculous planet! But where does water come from in space, and where to look for it in the Solar System? And further in the galaxy, around stars other than the Sun? On Earth, water has allowed life; has it been able to play this formidable role elsewhere?