NASA discovers surprising new features on Phaethon asteroid.

NASA researchers have found that asteroid 3200 Phaethon, which is the source of the annual Geminid meteor shower, has a tail made of sodium gas instead of dust, leading scientists to question whether some comets may actually be rocky asteroids like Phaethon. The asteroid's tail provides material for the Geminid meteor shower each December, and researchers believe a disruptive event a few thousand years ago caused Phaethon to eject the material making up the Geminid debris stream. An upcoming Japan Aerospace Exploration Agency mission called DESTINY+ is expected to fly past Phaethon later this decade.