We now know of thousands of planets circling other stars. These systems are very different than we expected they would be. We've found Jupiter-sized gas giant planets huddled close to their stars. We've found "super-Earths" two to 10 times the mass of our own planet. We've found planets orbiting double-star systems. It may be our own solar system that's the oddball in the universe.
But despite the strangeness, the question that drives us remains the same: Are there other planets out there that could have given rise to life?
Webb will study the atmospheres of these extrasolar planets — or exoplanets, as they're called — for the chemical fingerprints of water vapor, methane, ammonia, carbon monoxide, and carbon dioxide — the types of gases that were present on primitive Earth. Webb will examine how gas and dust disks around stars coalesce into planets, and define the raw materials of those disks with much greater precision than any previous telescope.