PBS
How Earth's First, Unkillable Animals Saved the World
They have survived every catastrophe and every mass extinction event that nature has thrown at them. And by being the little, filter-feeding, water-cleaning creatures that they are, sponges may have saved the world.
PBS
How Volcanoes Froze the Earth (Twice)
Over 600 million years ago, sheets of ice coated our planet on both land and sea. How did this happen? And most importantly for us, why did the planet eventually thaw again? The evidence for Snowball Earth is written on every continent...