They're losing sleep as the landing nears, wondering if it will be a success leading to groundbreaking science, or a $2.5-billion disaster.

NASA has dubbed the dizzyingly complex landing of its new Mars rover "seven minutes of terror" — a sequence of pyrotechnics, ropes and a "backpack" of engines that must work in meticulous choreography to give the mission a shot. Because of the distance, the sequence will be over by the time engineers receive a message that it has begun; Curiosity will already be on the ground, either ready to deliver groundbreaking science, or lying in a $2.5-billion wreck.

This weekend, as scientists were preparing their final push, Adam Steltzner — a leader of the landing team and a confident man with a booming voice and a skinny-Elvis pompadour — was asked which of the seven minutes was his favorite.

"Like any good parent," he said, clutching his chest, "I love each of those minutes equally." He has allotted himself an hour a day to think about it, he said — between 2:30 a.m. and 3:30 a.m., staring at the ceiling.