2011 L4 (PanSTARRS)

Tuesday, April 19, 2016 - 07:01 in Astronomy & Space

For millennia, people on Earth have watched comets in the sky. Many ancient cultures saw comets as the harbingers of doom, but today scientists know that comets are really frozen balls of dust, gas, and rock and may have been responsible for delivering water to planets like Earth billions of years ago.