Given the pace of discovery using Earth and spaceborne observatories, it's not too much of a stretch to assume that sooner or later a planet orbiting its parent star in the "habitable" zone, a region where liquid water is likely to exist, will be found. So let's assume that a planet has been found in this "Goldilocks" zone. How would we go about inspecting that planet to determine if there is, in fact, life present? What's next? Paul Gilster explains.