A discarded rocket stage, left adrift after delivering its payloads to the moon more than a year ago, will collide with the lunar surface Wednesday at 5,400 miles per hour — an unintended consequence of a step never taken. Near Einstein Crater, on the moon's near side, the impact will carve a new scar into an ancient landscape, and scientists will watch closely, not out of alarm, but out of necessity. As humanity accelerates its return to the moon, this accidental collision becomes an unexpected teacher, reminding us that the choices we make in space — including the ones we neglect — leave mar