Sixty-six million years ago, near what’s now the Yucatán Peninsula, a juvenile sauropod feasted on horsetail plants on a riverbank. Earth was a tropical planet. Behemoth and tiny dinosaurs alike soared its skies and roamed its lands while reptiles and tentacled ammonites swept its seas. But, in an instant, everything would change. Sean P. S. Gulick details one of Earth's most devastating periods. Lesson by Sean P. S. Gulick, directed by Jeff Le Bars, JetPropulsion.space