Nasa successfully crashed a spacecraft into an asteroid, accomplishing the goal of altering the asteroid’s course, a task which has never before been accomplished.
The ability to successfully alter the trajectory of an asteroid could potentially be life-saving for humanity in the future, should an asteriod of significant-enough size one day be detected on a collision-course with earth. A similar event is believed to have ended the era of dinosaurs, about 65 million years ago, demonstrating the existential threat to a species such an event could have.