CHEBARKUL, Russia — After a brilliant flash illuminated the sky on Friday morning like a second sun, Alyona V. Borchininova and several others in this run-down little town in the Siberian wilderness wandered outside, confused and curious.

They followed the light’s path to the town’s lakefront, where they trudged for about a mile over the open ice until they came to a startling sight: a perfectly round hole, about 20 feet in diameter, its rim glossy with fresh ice that had crusted on top of the snow.

“It was eerie,” Ms. Borchininova, a barmaid, said Saturday. “So we stood there. And then somebody joked, ‘Now the green men will crawl out and say hello.’ ”

Russians are still coming to terms with what NASA scientists say was a 7,000-ton chunk of space rock that hurtled out of the sky at 40,000 miles an hour, exploding over the Ural Mountains, spraying debris for miles around and, amazingly, killing no one.