Our Earth consists of silicate rocks and an iron core with a thin veneer of water and life. But the first potentially habitable worlds to form might have been very different. New research suggests that planet formation in the early universe might have created carbon planets consisting of graphite, carbides, and diamond. Astronomers might find these diamond worlds by searching a rare class of stars. More.
Is it worth pointing out that we don’t know of any planet that has life other than ours?
See also: Maybe if we throw enough models at the origin of life… some of them will stick?