In the mid-1980s, a group of American archaeologists pored over satellite images trying to understand what had become of the Mayan civilization that had once ruled over Mexico’s Yucatan Peninsula, discovered a pattern: a near-perfect ring of sinkholes -cenotes- about 200 kilometers across, encircling the Yucatecan capital, Merida, and port towns of Sisal and Progreso. A pattern created by an ancient asteroid explosion that one young NASA scientist thought may yield clues to the lost ocean and atmosphere of Mars. Defining Event in the History of Planet Earth When the researchers presented their findings to fellow satellite specialists at a scientific conference in Acapulco, Mexico, in 1988, one scientist in the audience, Adriana Ocampo, then a young planetary geologist at NASA, saw not just a huge ring, but a bullseye –the impact crater of an asteroid that hit with the force of 10 billion Hiroshima nuclear bombs that scarred the planet in ways still being revealed 66 million years on. An impact that ended the reign of dinosaurs and opened a pathway for the emergence of the human species. “It gave us a leg up to be able to compete, to be able to flourish, as we eventually did,” she said.