“do without” = lacking something essential
“If space travelers had to do without fresh water for very long, they wouldn’t be able to survive.”
“at the drop of a hat” = immediately, willingness to do something without delay
“I’d travel to the moon at the drop of a hat if I had the chance.”
What are three specific things that world governments can do, individually or collectively, to prevent or minimize the impact of future catastrophes such as huge meteors and asteroids of this kind on a global scale? Use the internet to research the topic of asteroid avoidance strategies or plans for planetary defense of such events.