Earth is teeming with life-and water makes it all possible. But elsewhere in the cosmos, life might be built from different chemicals that dissolve and assemble in some other liquid: perhaps methane, kerosene, or even chloroform. For now, it is not feasible for humans to set foot on those worlds and see what is there, but researchers are exploring some possibilities in labs here on Earth. The idea of a strange parallel form of life, whose cells do the same basic things as ours using a completely different chemistry, is not new to science. In fact, Isaac Asimov broached the subject in his 1962 essay "Not as We Know It: The Chemistry of Life." And in 2004, the same year the Cassini spacecraft entered Saturn's orbit, biochemist Steven Benner proposed that on a world like Saturn's moon Titan, life might use liquid hydrocarbons as a solvent (a liquid that can dissolve other substances), the way water is used on Earth. With new exoplanets joining the roster of known worlds every day, it is likely that some of them have oceans (or at least warm puddles) of hexane, ethers, chloroform, or other exotic liquids that might serve as a source of life, which we do not yet know.