On a Monday evening last September, a NASA spacecraft intentionally blasted into an asteroid in deep space. The goal was planetary defense — protecting our planet from the kind of wayward rock that could end civilization as we know it. The unprecedented moment seemed surreal, with a camera from the craft sending footage back to Earth of a large asteroid getting bigger and bigger until — pow! — impact. It was both incredible and credible — equal parts jaw-dropping and successful in its proof of concept.