Comets' heads can be green, but never their tails: After 90 years, we finally know why

Solving a 90 Year-Old Space Mystery: Why Comets’ Heads Can Be Green, but Never Their Tails

Body mass of animals shrank by 98% during last 1.5 million years

Comets’ heads can be green, but never their tails. After 90 years, we finally know why