Astatine is probably the rarest chemical element that you've never heard of or seen. It occurs on Earth only as the result of the radioactive decay of certain heavier elements. Elemental astatine has never been viewed, because a mass large enough to be seen (by the naked human eye) would be immediately vaporized by the heat generated by its own radioactivity. Click here to view the first image in today's viral picture gallery. Continue reading for a viral video showing what Jurassic Park would be like with cats instead of dinosaurs.