Six years ago today, an explosion and fire on the Deepwater Horizon oil rig in the Gulf of Mexico killed 11 workers and unleashed the largest oil spill in U.S. history. It also launched a massive scramble by scientists to understand the extent and impacts of the spill.

On April 20, 2010, the Deepwater Horizon, a drilling rig off the Louisiana coast, blew up. The explosion killed 11 people, and the resulting oil spill, the largest in U.S. history, killed hundreds of thousands of animals and produced 65,000 square miles of oil slicks off the coasts of Louisiana, Mississippi, Alabama and Florida.