Graphic shows plan to smash a small spacecraft into an asteroid to change its course. NASA Double Asteroid Redirection Test (DART) mission graphic.

Still defenseless Earth remains vulnerable to the Big One

By Jay Brodell

At any moment a large rock can plummet from space and wipe out all or part of civilization. That realization should put into perspective all other day-to-day concerns.

A quick look at the airless moon’s surface shows the battering celestial objects take. On Earth natural geological processes cover up impact craters from…