Comets’ heads can be green, but never their tails. After 90 years, we finally know why: The team…
Every so often, the Kuiper Belt and Oort Cloud throw galactic snowballs made up of ice, dust and rocks our way: 4.6-billion-year-old leftovers from the formation of the solar system.
These snowballs -- or as we know them, comets -- go…